 |
 Previous Article | Next Article 
The Journal of Neuroscience, April 1, 2002, 22(7):2718-2729
Gene Expression Profiling Reveals Alterations of Specific
Metabolic Pathways in Schizophrenia
Frank A.
Middleton1,
Karoly
Mirnics1, 2, 4,
Joseph
N.
Pierri2,
David A.
Lewis2, 3, and
Pat
Levitt1, 4
Departments of 1 Neurobiology,
2 Psychiatry, 3 Neuroscience, and
4 PittArray, University of Pittsburgh School of Medicine,
Pittsburgh, Pennsylvania 15261
 |
ABSTRACT |
Dysfunction of the dorsal prefrontal cortex (PFC) in schizophrenia
may be associated with alterations in the regulation of brain
metabolism. To determine whether abnormal expression of genes encoding
proteins involved in cellular metabolism contributes to this
dysfunction, we used cDNA microarrays to perform gene expression
profiling of all major metabolic pathways in postmortem samples of PFC
area 9 from 10 subjects with schizophrenia and 10 matched control
subjects. Genes comprising 71 metabolic pathways were assessed in each
pair, and only five pathways showed consistent changes (decreases) in
subjects with schizophrenia. Reductions in expression were identified
for genes involved in the regulation of ornithine and polyamine
metabolism, the mitochondrial malate shuttle system, the
transcarboxylic acid cycle, aspartate and alanine metabolism,
and ubiquitin metabolism. Interestingly, although most of the metabolic
genes that were consistently decreased across subjects with
schizophrenia were not similarly decreased in haloperidol-treated monkeys, the transcript encoding the cytosolic form of malate dehydrogenase displayed prominent drug-associated increases in expression compared with untreated animals. These molecular analyses implicate a highly specific pattern of metabolic alterations in the PFC
of subjects with schizophrenia and raise the possibility that
antipsychotic medications may exert a therapeutic effect, in part, by
normalizing some of these changes.
Key words:
microarray; neuroleptic; haloperidol; malate; ubiquitin; ornithine; polyamine; aspartate; citrate; transcarboxylic acid; mitochondria; prefrontal
| |
INTRODUCTION |
Alterations in the metabolism of the
dorsal prefrontal cortex (PFC) are well documented in studies of
schizophrenia (Berman et al., 1986 ; Weinberger et al., 1986; Andreasen
et al., 1992; Buchsbaum et al., 1992). It has been suggested that some
of these alterations may underlie the cognitive symptoms of the
disorder (Goldman-Rakic 1991; Park and Holzman 1992). For example,
blunted increases in glucose use and blood flow are seen in the dorsal PFC of subjects with schizophrenia while they perform cognitive tasks
compared with the large activations and blood flow increases seen in
normal subjects (Berman et al., 1986, 1992; Weinberger et al., 1986;
Andreasen et al., 1992; Buchsbaum et al., 1992; Callicott et al.,
1998). Considerable efforts have been made to determine the cellular
mechanisms that might underlie these apparent alterations in brain
metabolism in schizophrenia. Magnetic resonance spectroscopy studies
suggest that changes in the concentration of high-energy phosphate
molecules (including ATP, phosphocreatine, and phospholipid
metabolites) may be a common feature of schizophrenia, present even in
never-medicated subjects at the onset of clinical symptoms (Pettegrew
et al., 1991; Bertolino et al., 1998; Cecil et al., 1999; Keshavan et
al., 2000; Stanley et al., 2000). Other studies have reported altered
expression of one or more metabolic genes, or the levels of proteins
for which these genes code, in postmortem brain tissue from subjects
with schizophrenia (Marchbanks et al., 1995; Mulcrone et al., 1995;
Whatley et al., 1996; Prince et al., 1999; Maurer et al., 2001).
It is possible that the changes in prefrontal metabolism reported in
schizophrenia may be related to changes in synaptic structure and
function. This is attributable to both the high metabolic demands placed on neurons by the processes involved in synaptic communication and the considerable evidence indicating synaptic abnormalities in schizophrenia (Perrone-Bizzozero et al., 1996; Glantz and Lewis, 1997, 2000; Harrison 1999; Karson et al.,
1999; Selemon and Goldman-Rakic 1999). In a previous report, we used cDNA microarrays to assess potential alterations in >250 different gene groups in six subjects with schizophrenia (Mirnics et al., 2000,
2001a). We showed that genes related to presynaptic secretory function,
and the gene encoding the regulator of G-protein signaling 4 (RGS4),
were consistently decreased in subjects with schizophrenia. The data
suggested that schizophrenia may be a disease with fundamental dysfunction of synaptic communication (Mirnics et al., 2000, 2001a,b). In the present study, we wished to determine whether transcript levels
in more than 70 different gene groups involved in cellular metabolism,
which could impact the quality of neuronal communication, were altered
in a larger sample of subjects with schizophrenia and whether the
effects on these gene groups were interrelated. The present report
demonstrates that only five of the metabolic pathways examined showed
consistent changes (decreases) in subjects with schizophrenia and that
four of these groups are linked together by the presence of overlapping
gene members.
| |
MATERIALS AND METHODS |
Ten subjects with schizophrenia and 11 matched control subjects
were used for both the microarray and in situ hybridization studies (Table 1). One of the subject
pairs (794c/665s) used in the microarray studies did not have tissue
available for in situ hybridization from the control
subject, so another matched control subject (806c) was substituted. The
two groups of normal subjects and subjects with schizophrenia did not
differ in mean ± SD age at time of death (47.3 ± 14.5 and
46.0 ± 12.6 years, respectively), postmortem interval (PMI)
(17.4 ± 5.5 and 18.6 ± 6.7 hr, respectively), brain pH
(6.83 ± 0.21 and 6.84 ± 0.35, respectively), or tissue
storage time at  80°C (57.7 ± 16.6 and 67.7 ± 21.8 months, respectively). Subject pairs were matched for gender (eight
males and two females per group), and eight of the pairs were matched
for race. Among the group of subjects diagnosed with schizophrenia,
eight were receiving antipsychotic medications, three had a history of
alcohol abuse or dependence, and one had a history of drug dependence
at the time of death. Two of the subjects with schizophrenia died by
suicide. Among the control subjects, one (635c) had a past history of
depressive disorder, not otherwise specified, and another had a history
of alcohol abuse or dependence at the time of death. Consensus
DSM-IIIR (Diagnostic and Statistical Manual of Mental Disorders,
1987) diagnoses for all subjects were made using data from clinical records, toxicology studies, and structured interviews with surviving relatives, as described in detail previously (Volk et al.,
2000). Six of the subject pairs used in the present study were studied previously using cDNA microarrays (Mirnics et al., 2000, 2001a,b). One
of these "old" pairs (685c/622s) and four additional subject pairs
not studied previously with microarrays were analyzed using a more
updated microarray platform for the current study (see Microarray
experiments). We note that, since publication of these previous
studies, we performed an extensive reevaluation of all potential
subject pairings to obtain the best possible pairs (based on gender,
age, postmortem interval, and brain pH) for a much larger set of
patients and controls in future microarray studies. This necessitated
that some of the previous pairings used for in situ
hybridization follow-up studies were rearranged.
Microarray experiments
Methods of tissue preparation, nucleic acid isolation, sample
labeling, microarray hybridization, and initial data analysis were the
same as those reported previously (Mirnics et al., 2000). Briefly, 200 ng of mRNA was reverse transcribed using Cy3- or Cy5-labeled
fluorescent primers. Samples from matched subject pairs were combined
and hybridized onto the same UniGEM V or UniGEM V2 cDNA microarray
(Incyte Genomics Inc., Fremont, CA). Each UniGEM V array contained
>7800 unique and sequence-verified cDNA or expressed sequence
tag elements, whereas each UniGEM V2 array contained nearly
10,000 elements, including >7000 of the genes present on the UniGEM V. If a transcript was differentially expressed, the cDNA feature on the
array bound more of the labeled target from one sample than the other,
producing either a greater Cy3 or Cy5 signal intensity. Microarrays
were scanned under Cy3-Cy5 dual fluorescence, and the resulting images
were analyzed for signal intensity. Only genes whose signal intensity
was 3.5-fold greater than background signal intensity were called
present. The operators performing the labeling, hybridization,
scanning, and signal analysis were blind to the specific category to
which each sample belonged.
Individual gene expression analysis. Because of the inherent
variability in the distribution of expression ratios from experiment to
experiment and the use of two different microarray platforms with
different published confidence levels, we converted the balanced differential expression (BDE) ratio (of Cy3/Cy5 intensity) for each
gene into a standard Z score for each experiment according to the following formula:
After this normalization procedure, the mean Z score
for each array comparison was 0.0, with an SD of 1.0. To
identify the most consistently affected metabolic-related genes in
these experiments, we computed a "Z load score" for each
gene, which was the product of the average Z score of a gene
across all subject pair comparisons and the number of comparisons in
which that gene was significantly changed at the 0.05  level (i.e.,
had a Z score that exceeded ±1.65) (Table
2).
Gene group design. Metabolism gene groups were constructed
using the Kyoto Encyclopedia of Genes and Genomes release 19.0, July
2001 (www.genome.ad.jp/kegg/metabolism.html). Several additional groups
were also constructed using standard biochemistry texts and review
articles (Alberts et al., 1989; Siegel et al., 1989; Darnell et al.,
1990; Mathews and van Holde, 1990; Kauppinen and Alhonen, 1995;
Bernstein and Muller, 1999). These custom designed groups included
genes involved in the five different subunits of the electron transport
chain (ETC), the malate shuttle system, the ornithine-polyamine
system, and ubiquitin metabolism gene families. The list of genes
in these groups has been made available for viewing at
http://www.neurobio.pitt.edu/Levitt_JN_Genes.htm.
Gene group expression analysis. Analysis of gene group
expression was performed by ANOVA, using a post hoc
test (Scheffe's) to compare the distribution of Z scores
for all genes in a group with the distribution of Z scores
for all of the genes on an array. The significance values
(p values) of these post hoc tests were entered into a table that was pseudocolored according to the level of
the effect (Fig. 1). We found that this
method of gene group expression analysis provides a more conservative
estimate of significant gene group effects compared with other methods
that we used, such as repeated t test comparisons or
 2 analysis using confidence interval
binning. To determine whether there were significant interactions among
gene groups, the p values for each gene group were
normalized by using the log of each p, with the sign
positive or negative depending on the direction of the change in
expression. A correlation matrix was then computed among the 71 different gene groups and principal component analysis (PCA)
subsequently applied to the matrix. The factor loadings for the five
gene groups that were significantly changed in five or more comparisons
were displayed in a radial plot (see Fig. 3A).
View larger version (56K):
[in this window]
[in a new window]
|
Figure 1.
Metabolic gene group expression in
schizophrenia. Genes in 71 different metabolic groups, belonging to
several different categories of cellular functions, were analyzed in 10 subjects with schizophrenia and their matched controls. For each gene,
a pairwise differential expression ratio was calculated and converted
into a Z score for each array comparison. The
Z score distribution of all of the genes present in each
gene group was then compared with the Z score
distribution of each array using ANOVA, and the significance of the
differences was estimated with a post hoc paired
Scheffe's F test. The p values from
these tests were entered into a table that was pseudocolored according
to the level of the effect (key at the bottom). An average og 7.2 of the 71 gene groups were significantly
changed in each of the five pairs compared using the UniGEM V
microarray (right), whereas an average of 7.6 gene
groups were changed in each of the five pairs compared using the UniGEM
V2 microarray (left). Only five genes groups exhibited
changes in expression (decreases) in five or more comparisons
(indicated by arrowheads). The decreases in these five
gene groups reached significance slightly more often in the UniGEM V2
comparisons (mean, 3.2 of 5) than the UniGEM V comparisons (mean, 2.2 of 5), although a complete shift of the mean Z scores of
these groups was evident in all comparisons (see Fig. 2).
|
|
In situ hybridization analysis
The same tissue blocks used for the microarray experiments were
used to obtain sections for in situ hybridization. Area 9 was identified based on surface landmarks as described previously (Glantz and Lewis, 2000). After histological verification of the regions, 20 µm sections were cut with a cryostat at 20°C, mounted onto gelatin-coated glass slides, and stored at 80°C until use. The
slides were coded so that the investigator performing the analysis was
blinded to the diagnosis of the subjects. Three slides from each
subject were used to examine the expression of each of four different
genes: malate dehydrogenase type 1, cytosolic (MAD1);
glutamate-oxaloacetate transaminase type 2, mitochondrial (GOT2);
ornithine decarboxylase antizyme inhibitor (OAZIN); and ornithine
aminotransferase (OAT). These genes were chosen for in situ
hybridization analysis because of their consistent changes in
expression in the microarray experiments (Table 2). To generate the
riboprobes for in situ hybridization, double-stranded cDNA containing highly unique 699-878 bp sequences of each gene were initially amplified from normal human brain cDNA using custom-designed primers in a standard PCR reaction [OAZIN, nucleotides (nt) 1146-1845 of D88674; OAT, nt 84-962 of M1496; MAD1, nt 168-905 of U20352; and
GOT2, nt 458-1298 of M22632]. After cloning of the PCR products and
sequence verification of selected colonies,
[35S]-labeled riboprobes were
synthesized. During hybridization, ~2-3 ng of probe (~1-2 × 106 dpm) were used per slide in a total
volume of 90-100 µl. All other methods used were described
previously (Campbell et al., 1999; Mirnics et al., 2000). After
hybridization (16 hr, 56°C) and film exposure [42 hr, BioMax MR
(Eastman Kodak, Rochester, NY)] high-resolution scans of each
film image were used for quantification of signal with Scion NIH Image
(version 4.0b). In addition, dark-field images were captured from the
slides that had been dipped in radiographic emulsion (14 d, NTB-2;
Eastman Kodak). Through all procedures, subject pairs were always
processed in parallel. Hybridization of sections with sense riboprobe
did not result in detectable signal. The absolute levels
(disintegrations per minute per square millimeter) of
radioactive probe labeling were calculated using [14C]-labeled standards that had been
cross-calibrated to known quantities of
[35S]-containing brain matter. The
baseline levels for these measurements were set at the 0 dpm level
included on each standard.
Data from the in situ hybridization experiments were
analyzed using multivariate ANOVA, repeated-measures ANOVA, and
analysis of covariance with diagnosis as the main effect and brain pH, PMI, and tissue storage time as covariates. All of these models were
applied both with and without subject pair as a blocking factor.
Post hoc tests were performed using Fisher's protected least significant difference, Games-Howell, and Scheffe's methods. All models yielded similar results for the effect of diagnosis on
expression level differences. Levels of gene expression were also
subsequently analyzed by logistic regression.
Monkey experiments. To formally examine the potential
influence of antipsychotic medication on the expression of MAD1, OAT, GOT2, and OAZIN, we also used four pairs of male cynomolgus
(Macaca fascicularis) monkeys, matched for age and weight,
as subjects for in situ hybridization analysis in areas 9 and 46. In each pair, one animal was treated for 9-12 months with the
antipsychotic medication haloperidol decanoate as described previously
(Pierri et al., 1999). Serum levels were in the therapeutic range for the treatment of schizophrenia. Extrapyramidal symptoms were
effectively managed by maintenance administration of benztropine
mesylate. Tissue sections from these animals were acquired and used in
parallel with the human material.
All procedures were reviewed and approved by the appropriate
institutional review boards or the institutional animal care and use committee.
| |
RESULTS |
Most of the metabolism gene groups that we analyzed did not
display significant differences in transcript levels between
schizophrenic and control subjects (Fig. 1). However, five gene groups
did display significant alterations (p < 0.05)
in transcript levels in five or more of the 10 array comparisons (Fig.
1). These included the malate shuttle, transcarboxylic acid (TCA)
cycle, ornithine-polyamine, aspartate-alanine, and ubiquitin
metabolism groups. Several other gene groups also displayed
significantly decreased expression in fewer than five array
comparisons. No metabolic gene groups, however, showed significant
increases in expression in more than two array comparisons (Fig. 1).
When analyzed across all subjects with schizophrenia, the mean
expression levels of each of the five most affected gene groups were
consistently and significantly decreased compared with matched
controls (Figs. 1, 2). In addition, analysis of the mean pairwise Z score distributions for
these gene groups revealed two distinct and highly correlated patterns of decreased expression in the subjects with schizophrenia (Fig. 2).
The first of these patterns was present in seven of 10 array comparisons with primary intercorrelations ranging from 0.77 to 0.99. The second pattern was present in two array comparisons (630c/566s and
604c/581s; r = 0.68). Only one array comparison failed
to demonstrate significant similarity with other array comparisons
(Fig. 2, 558c/317s).
View larger version (33K):
[in this window]
[in a new window]
|
Figure 2.
Mean pairwise Z score
distributions: five highly affected and one unaffected gene group. The
distribution of mean Z scores for the five most
consistently affected gene groups (see Fig. 1) is shown for each array
comparison, along with the mean Z scores for an
unaffected gene group, RNA polymerases (RNA Poly).
Interestingly, the mean Z score distributions for the
five most affected gene groups was highly correlated among seven of the
10 subject pairs (Pearson's R range, 0.77-0.99).
Asp/Ala, Aspartate-alanine metabolism;
Orn/PA, ornithine-polyamine metabolism.
|
|
Correlated metabolic group effects
To examine whether there were interactions among the effects on
different metabolic gene groups, we next computed a correlation matrix
using the log of the p value for each gene group and
performed a varimax PCA on this matrix. PCA permits one to search for
significant relationships between multiple data sets and reduces the
complexity of these relationships to a small number of factors that
best describe the variance of the data. The PCA we performed produced eight factors that described >99.9% of the variance of the
correlation matrix for the 71 gene groups. The degree to which the
effects on different gene groups are related to each factor is provided by the oblique factor weights for each gene group, which are the correlation of each variable with each factor. Examination of the
oblique factor weights in our PCA analysis revealed that the effects on
the malate shuttle, TCA cycle, and ubiquitin groups were highly
correlated (Fig. 3A,
Factor 2). Factor 3, in contrast, more accurately described
the effects on aspartate-alanine and ornithine-polyamine metabolism
(Fig. 3A, Factor 3). This analysis also revealed
that a number of gene groups with decreases in expression in fewer than
five schizophrenic subjects had effects that were correlated with those
of the more significantly affected gene groups. For example, the
tyrosine and cysteine metabolism gene groups exhibited significant
decreases in expression in three schizophrenic
subjects, with the effects on all 10 subjects highly correlated with
factor 2 (oblique factor weights 0.977 and 0.827, respectively).
Likewise, expression of glycolysis genes was also significantly
decreased in three schizophrenic subjects, with effects that were
highly correlated with factor 3 (oblique factor weight 0.805).
View larger version (15K):
[in this window]
[in a new window]
|
Figure 3.
Correlations and connections between affected gene
groups. A, To estimate the mathematical relationships
between the effects on different gene groups, the normalized
p values from Figure 1 were used to calculate a
correlation matrix and perform a PCA. The PCA revealed strong
relationships between the effects on the malate shuttle, TCA (citrate)
cycle, and ubiquitin metabolism gene groups (Factor 2)
and between aspartate-alanine metabolism and ornithine-polyamine
metabolism (Factor 3). Variance proportions for factors
1-8 were 0.308, 0.233, 0.169, 0.091, 0.069, 0.055, 0.054, and 0.020, respectively. B, Connections, in the form of shared
genes, existed between four of the five most affected gene groups. The
size of these gene groups are drawn to scale, with the presence of
significantly affected overlapping genes indicted in
yellow and nonsignificantly affected overlapping genes
shown in gray.
|
|
Overlap in gene membership between different metabolic groups is one
possible explanation for the apparent similarity of statistical effects
on different gene groups; that is, a few genes whose changes were
robust might impact multiple gene groups. To further probe this issue,
we examined the overlap in gene membership among the most consistently
affected gene groups (Fig. 3B). Interestingly, of the four
genes comprising the malate shuttle group that were present on the
array, two genes were part of the TCA group (n = 13 genes) and the other two genes were part of the aspartate-alanine group (n = 16 genes) (Fig. 3B, Table 2).
Each of these four shared genes was significantly decreased in most
schizophrenic subjects compared with controls. The ornithine-polyamine
group (n = 18 genes) also shared two different genes
with the aspartate-alanine group. These particular genes, however,
were not significantly affected in schizophrenic subjects. The
ubiquitin group (n = 47 genes) did not share any genes
with the other metabolic gene groups. These observations, combined with
our analysis of the statistical effects on different gene groups,
indicate that simply sharing one or a few genes is insufficient to
explain the effects we described. In many cases, groups with a high
degree of overlap in membership do not have similar statistical effects
(e.g., tyrosine and phenylalanine gene groups; ornithine-polyamine and
urea cycle gene groups). Conversely, many of the gene groups with the
highest correlated effects do not have any genes in common (e.g.,
ubiquitin and tyrosine; ubiquitin and malate shuttle).
Although small overlaps in group membership do not appear to produce
correlated effects on different gene groups, they do establish real
biological links between them. Of the five different metabolic cascades
we identified as significantly affected in five or more array
comparisons, we were able to establish biological links between four of
these groups at the single gene level, with the lone exception being
the ubiquitin gene group (Fig. 2B). These relationships may have important biological significance (see Discussion).
In situ hybridization verification
We examined the expression of some genes that belonged to more
than one significantly affected gene group, as well as some genes that
belonged to only a single gene group, to verify the decreases in
expression observed in the microarray analysis. To determine
the individual genes that had the most robust changes in
our comparisons, we ranked all of the metabolic-related genes according
to their Z load scores (Table 2; see Materials and Methods).
Of the top 10 genes identified by this method, the transcripts encoding
MAD1, OAT, GOT2, and OAZIN were selected for additional analysis using
in situ hybridization. Two of these transcripts (OAT and
OAZIN) were members of a single gene group (ornithine-polyamine metabolism), whereas the other two transcripts belonged to more than
one gene group (Table 2).
In situ hybridization analysis confirmed the microarray
finding that expression of each of these four genes was significantly decreased (p < 0.05) in the PFC of the subjects
with schizophrenia (Fig. 4).
Moreover, there was no interaction between these decreases and
other subject characteristics, such as brain pH, PMI, or tissue storage
time. The decreased expression was present in the majority of the 10 subject pairs for each gene (Fig. 5).
View larger version (14K):
[in this window]
[in a new window]
|
Figure 4.
In situ hybridization confirms
microarray data. Four genes (OAZIN, OAT, MAD1, and GOT2) were chosen
for verification based on their consistency in changes (see Table 2).
The expression of these genes was significantly decreased in both the
in situ hybridization (A) and
microarray (B) studies of 10 subjects with
schizophrenia. In both A and B, the
pairwise expression of each gene is plotted as a ratio of the level in
the control subject compared with the level in the subject with
schizophrenia. Genes expressed at a higher level in controls are
located below the unity line, whereas genes expressed at a higher level
in subjects with schizophrenia are located above the unity line. Levels
of expression in A are in disintegrations per minute per
square millimeter, and levels in B represent balanced
fluorescent signal intensity.
|
|
View larger version (28K):
[in this window]
[in a new window]
|
Figure 5.
Pairwise expression differences in metabolic gene
expression. Each of the four metabolic genes we examined was
significantly decreased in subjects with schizophrenia, using both
paired and unpaired ANOVA comparisons. Mean levels of expression for
each subject group are indicated by the black bars. Mean
pairwise differences in expression for subjects with schizophrenia are
given in the boxes at the bottom of each
panel.
|
|
Each of the genes we examined by in situ
hybridization displayed a distinct
pattern and intensity of hybridization (Figs. 6,
7). For MAD1, nearly all cellular
cortical layers contained moderate to high levels of expression, with
very low levels of expression in the white matter. GOT2, another malate
shuttle gene, displayed almost uniformly low levels of expression
across all cortical layers. In contrast, OAT was highly expressed
throughout most cellular cortical layers, with occasional increases in
layer V present in some subjects and a low level of expression in the underlying white matter. OAZIN also displayed its highest expression in
layer V, with low levels of expression in other cortical layers and a
faint signal in white matter. Notably, the decreased expression of
these four genes that we observed in subjects with schizophrenia did
not appear to preferentially affect specific cortical layers.
View larger version (87K):
[in this window]
[in a new window]
|
Figure 6.
Laminar localization of transcript expression.
Each of the four genes examined was expressed in neurons, with little
or no signal present in white matter. These genes exhibited different
patterns and intensities but were all decreased in subjects with
schizophrenia (right) compared with control subjects
(left). Note that all of photomicrographs were taken
using identical radiographic emulsion exposure times and identical
illumination conditions. Roman numerals indicate
cortical laminas.
|
|
View larger version (99K):
[in this window]
[in a new window]
|
Figure 7.
Selective increases in MAD1 expression in
haloperidol-treated monkeys. None of the four genes we examined in
haloperidol-treated monkeys (A) exhibited the
same significant decreases in expression as subjects with schizophrenia
(B). However, one of these genes (MAD1) exhibited
significant increases in expression. C, Enlarged views
of the dorsomedial convexity of the PFC illustrating the change in MAD1
expression in medial area 9. The increased expression of MAD1 was
specific to deep cortical layers. *p < 0.05.
|
|
Logistic regression classification
Because of the potentially important role of OAT, OAZIN, MAD1, and
GOT2 in the pathophysiology of schizophrenia, we also performed a
logistic regression classification test with our in situ
hybridization data. This analysis revealed that, as a group, the levels
of expression of these four genes in the PFC correctly classified 75%
of the subjects in our study as either affected or unaffected. This
degree of accuracy is comparable with that achieved when analyzing
expression levels of the single most changed gene in our microarray
analysis, RGS4 (Mirnics et al., 2001a), by logistic regression
classification (data not shown). Future studies will be necessary to
determine the disease specificity of the changes we reported in the
present study, but they support the concept that analyzing gene
expression patterns in postmortem samples may be of value in
identifying a distinctive molecular neuropathology of schizophrenia.
Gene expression in haloperidol-treated monkeys
Consistent changes in gene expression in subjects with
schizophrenia may reflect either a component of the disease process or
a consequence of the pharmacological treatment of the disorder. In situ analysis of gene expression in monkeys treated
chronically with haloperidol indicated that none of the four genes we
examined in subjects with schizophrenia was significantly decreased in an animal model of the treatment of the disorder (Figs. 6, 7). One of
these four genes (OAZIN) did show marginal decreases, which may have
reached significance with a larger sample size. In contrast to the lack
of significant decreases in expression, we observed an unexpected
increase (p < 0.05) in the expression of the
MAD1 transcript in the PFC of haloperidol-treated monkeys (Figs. 6, 7).
This increase in expression averaged over 40% on a pairwise basis
(Fig. 7B) and was most evident in deep cortical layers (Fig. 7C). Although we recognize that no animal model can
accurately mirror the pharmacotherapy of schizophrenia, we cautiously
interpret these data to indicate that many of the changes in metabolic
gene expression we observed in subjects with schizophrenia are not a
direct result of treatment with antipsychotic medication.
| |
DISCUSSION |
The use of cDNA microarrays provides an opportunity to assess, in
a broad manner, potential metabolic alterations in schizophrenia at the
molecular level. Our analysis has revealed a consistent and significant
decrease in the expression of genes encoding proteins involved in the
mitochondrial malate shuttle, the transcarboxylic acid cycle, aspartate
and alanine metabolism, ornithine and polyamine metabolism, and
ubiquitin metabolism. Interestingly, many of these effects were highly
correlated with each other and with other biologically related, but
less consistently affected, gene groups. The ranking of metabolic genes
by Z load score and the analysis of gene overlap between
different affected metabolic gene groups revealed that alterations in
specific genes may be central to the metabolic pathophysiology of
schizophrenia. In addition, because of the important relationship that
exists between cellular metabolism and synaptic activity in the brain,
these findings converge with our recent studies demonstrating reduced
expression of gene groups involved in presynaptic function (Mirnics et
al., 2000) and the reduced expression of RGS4, a protein involved in
postsynaptic signaling (Mirnics et al., 2001). Together, the data
suggest that deficits in neuronal communication may contribute to the
core pathophysiology of schizophrenia.
Biological significance
At the chromosomal level, many of the individual metabolic
transcripts we identified as abnormally expressed in subjects with schizophrenia are located on cytogenetic loci that are directly linked
or associated with the disorder, including 1q32-44, 5q11-13, 8p22-21, 17q21, and 22q11-13 (Thaker and Carpenter, 2001). In addition, previous reports suggest that mitochondrial genes are expressed at abnormal levels in schizophrenia (Marchbanks et al., 1995;
Mulcrone et al., 1995; Whatley et al., 1996; Prince et al., 1999;
Maurer et al., 2001). Thus, it is possible that some metabolic-related genes may prove to be bona fide susceptibility genes. However, whether
these transcriptional changes in metabolic gene groups reflect primary
or secondary changes, they clearly have the potential to alter neuronal
metabolism and activity, thereby contributing to defects in neuronal communication.
Our findings indicate that a number of biologically related and
mitochondria-dependent processes are affected in schizophrenia. Specifically, we found that gene groups related to energy shuttles and
oxidative metabolism, as well as certain amino acid metabolic pathways,
exhibit reduced expression. Previous studies, using protein, enzyme
activity, and transcript level analyses, have demonstrated
abnormalities in many of these same gene groups and some of the same
genes in subjects with schizophrenia (see below).
Malate shuttle and transcarboxylic acid metabolism
In a study published over 35 years ago, serum malate dehydrogenase
activity was reported to be significantly diminished (~25%) in 50 subjects with schizophrenia compared with 10 controls (Burlina and
Visentin, 1965). These findings are consistent with our data on the
decreased expression of MAD1 in schizophrenia. The potential biological
consequences of a decrease in malate dehydrogenase activity, and a
general decrease in the activity of the malate shuttle, are quite
significant. First, one of the most important functions of the malate
shuttle is to transfer hydrogen ions [in the form of reduced
nicotinamide adenine dinucleotide (NADH)] from the cytoplasm
into the mitochondria. Therefore, schizophrenia may be associated with
increased [H+]-reducing equivalents in the cytosol. Increases in
cytosolic [H+] are known to decrease the activity of the major
rate-limiting enzyme of glycolysis, 6-phosphofructokinase (Mathews and
van Holde, 1990). Thus, decreased malate shuttle activity in the PFC of
subjects with schizophrenia could produce secondary effects on the rate
of glycolysis, perhaps contributing to the reduced glucose use observed
in the PFC of these subjects while they are engaged in cognitive tasks
(Berman et al., 1986; Weinberger et al., 1986; Andreasen et al.,
1992; Buchsbaum et al., 1992).
Second, the malate shuttle system also acts in concert with a
malate-citrate exchange system that is part of the TCA cycle and
serves as an entry point for fatty acid synthesis. In fact, the malate
shuttle system and the TCA system both contain the gene for MAD1. If
the malate shuttle activity is reduced and the activity of the
malate-citrate exchange system is reduced as well, one might expect to
find a loss in cytosolic citrate and decreased activity of other TCA
proteins. In our data, we found a reduction in the expression of at
least three other TCA genes in subjects with schizophrenia: isocitrate
dehydrogenase 3 (average Z of 1.79; Z load of
5.37), ATP citrate lyase (average Z of 1.39;
Z load of 4.18), and dihydrolipoamide dehydrogenase (average
Z of 1.18; Z load of 3.53). Together, these
findings suggest that TCA metabolism is significantly affected in
schizophrenia. Given the role that TCA metabolism plays in fatty acid
synthesis, these findings may help explain the reductions in markers of
fatty acid metabolism that have been reported in several studies
of subjects with schizophrenia (Pettegrew et al., 1991; Fenton et al.,
2000; Keshavan et al., 2000; Stanley et al., 2000; Yao et al., 2000;
Assies et al., 2001).
Finally, decreased malate shuttle activity could directly alter
cytosolic levels of aspartate and glutamate, given the role that the
malate shuttle plays in the exchange of cytosolic malate for
mitochondrial -ketoglutarate and then (after transamination of
-ketoglutarate into glutamate) the exchange of cytosolic glutamate for mictochondrial aspartate. Alterations in cytosolic aspartate and
glutamate levels could affect not only the metabolism of these molecules (see below) but also ornithine-polyamine metabolism (see below).
Aspartate-alanine metabolism
In addition to the connection, through substrate levels,
between the malate shuttle system and aspartate metabolism described above, these groups also share two genes, GOT1 and GOT2. Both of these
genes exhibited reduced expression in subjects with schizophrenia (GOT2
average Z of 1.39, Z load of 8.33; GOT1 average
Z of 0.95, Z load of 1.9), with the changes in
GOT2 ranking among the most consistent metabolic gene findings (Table
2). Other genes in the aspartate-alanine metabolism group also showed
consistent and occasionally significant decreases in expression,
including asparaginyl-tRNA synthetase (average Z of 1.11;
Z load of 3.33) and asparagine synthetase (average
Z of 1.18; Z load of 1.18). The broad effect on
this metabolic gene group may help explain the findings of reduced
levels of N-acetyl-L-aspartate, an
important intermediary molecule of aspartate metabolism, in subjects
with schizophrenia (Deicken et al., 1997; Bertolino et al., 2000; Auer et al., 2001).
Ornithine-polyamine metabolism
We found decreased expression of several genes involved in
ornithine-polyamine metabolism in subjects with schizophrenia. These expression deficits are consistent with a number of
previous studies demonstrating alterations in this system in
schizophrenia, particularly in peripheral tissues (Flayeh, 1988;
Svinarev, 1987; Ramchand et al., 1994; Berstein and Muller, 1999) (but
see Gilad et al., 1995). Our ranking of the changes in expression of
genes related to metabolism (Table 2) revealed that three of the genes involved in ornithine-polyamine metabolism were among the most consistently reduced in schizophrenia. Specifically, the transcripts encoding OAZIN, µ-crystallin, and OAT were de-creased in the
majority of subjects with schizoprhenia (average
Z scores of 2.49, 2.22, and 3.13, respectively; Z load scores of 17.43, 15.53, and 12.53, respectively). Our in situ hybridization data confirmed the
decrease in expression of both OAZIN and OAT, which participate in the regulation of polyamine production. The precise role of µ-crystallin has not been studied in the brain, but this protein is a mammalian homolog of ornithine cyclodeaminase (OCD; EC 4.3.1.12). OCD is present
in the retina and other neural tissues and catalyzes the conversion of
L-ornithine to L-proline
(Kim et al., 1992). In contrast to OCD-µ-crystallin, the roles of
OAZIN and OAT have been well documented in the brain. The ornithine
decarboxylase (ODC) antizyme is the key regulator of ODC enzyme
activity in the brain and hence a major inhibitor of polyamine
production. The antizyme inhibitor (OAZIN) normally boosts polyamine
production by decreasing the ability of the antizyme to inhibit ODC
activity. There are reports of increased levels of polyamines in the
blood and peripheral tissues of schizophrenic subjects, as well as
increased levels of ODC expression in the rodent neonatal ventral
hippocampal lesion model of schizophrenia (Bernstein et al., 1998) (but
see Lipska et al., 1993). Although this is a complex enzyme system, with multiple positive and negative feedback components, it is possible
that the decreases in OAZIN and OAT transcript expression we observed
in subjects with schizophrenia reflect compensatory mechanisms to
reduce elevated polyamine levels or simply an attempt by neurons in the
dorsal PFC to downregulate the entire ornithine-polyamine system.
Interestingly, not only does ornithine-polyamine metabolism affect
glutamate and aspartate metabolism, but the products of this metabolic
pathway (polyamines) can serve directly as potent NMDA receptor
antagonists (Williams et al., 1991; Kashiwagi et al., 1997) (for
review, see Williams, 1997). Thus, decreased levels of glutamate and
aspartate, accompanied by decreases in ODC activity and polyamine
production, may be characteristic of the metabolic state of the brain
in schizophrenia and additional evidence of convergent changes in
metabolic and synaptic-related transcripts.
Ubiquitin metabolism
Decreased expression of at least two genes involved in ubiquitin
metabolism (ubiquitin specific protease 9 and ubiquitin C-terminal esterase L1) was reported recently in another microarray study of PFC
gene expression in schizophrenia (Vawter et al., 2001). Our ranking of
the most changed metabolic genes (Table 2) includes one of these genes
(ubiquitin C-terminal esterase L1; average Z of 1.71;
Z load of 6.82), as well as ubiquitin-specific protease 14 (average Z of 1.87; Z load of 9.33). Thus, at
least some of the expression deficits we observed in our patient sample
were present in a separate cohort of schizophrenic subjects studied in
a different laboratory with another microarray platform. In addition,
our analysis extends and integrates these observations on the ubiquitin
cascade into a set of highly correlated metabolic group effects that
occur in the same subjects. Our factor analysis demonstrated that the
effect on ubiquitin metabolism was highly correlated with the effects
on the malate shuttle and TCA metabolism gene groups. Because the
ubiquitin pathway marks proteins for degradation and plays an important
role in the regulation of synaptic formation and activity (Hegde et
al., 1997; DiAntonio et al., 2001), this molecular insult could reflect
yet another point of convergence for altered neural communication in schizophrenia.
Relevance to synaptic function
In a previous study, we found that reduced expression of
transcripts encoding synaptic proteins was a common feature of subjects with schizophrenia (Mirnics et al., 2000, 2001a,b). Interestingly, the
vast majority of measurable metabolic flux in the brain occurs at
synapses (Sokoloff, 1977; Nudo and Masterton, 1986). Indeed, many of
the processes that are essential to synaptic vesicle docking and
release are energy dependent and require high levels of ATP production.
In our previous study, two of the most consistently affected genes
within the presynaptic group (N-etylmalemide-sensitive factor and vacuolar ATPase) were ATPases that use the energy
provided by synaptically localized mitochondria to help maintain a
readily releasable pool of synaptic vesicles. Together with our present results, these findings indicate that neurons within the PFC of schizophrenic subjects will likely have difficulty meeting the normal
metabolic demands placed on them by neural activity.
Effects of antipsychotic medication on metabolic
gene expression
One of the unexpected findings in our analysis was the significant
increase in expression of MAD1 in the PFC of monkeys in response to
chronic haloperidol treatment. This finding indicates that the
decreased expression of the MAD1 transcript in subjects with
schizophrenia is not attributable to drug treatment. However, the data
raise the possibility that antipsychotic treatment in these subjects
targets MAD1, either directly or indirectly, and thus could compensate
for the normally deficient expression in schizophrenia. Previous
studies have shown that haloperidol administration produces increases
in certain metabolic enzymes and upregulates neural activity in some
brain regions (Prince et al., 1997a,b). Thus, the selective targeting
of malate shuttle or TCA cycle proteins and genes may provide a means
for therapeutic manipulation of these metabolic processes in the PFC of
subjects with schizophrenia.
Conclusion
In summary, we showed that subjects with schizophrenia exhibit a
common set of metabolic transcriptional abnormalities. These abnormalities involve decreases in a small number of biologically related cascades involved in energy shuttles and amino acid metabolism, fatty acid synthesis, neurotransmitter metabolism, and glycolysis. We
suggest that the effects on the malate shuttle system may serve as a
primary site of dysfunction or keystone effect, which, together with
the other molecular alterations, disrupts neuronal communication of
specific brain circuits. At least one of the malate shuttle genes
exhibits increased expression in response to antipsychotic medication,
raising the possibility that this treatment may help normalize brain
metabolism through actions on this system.
| |
FOOTNOTES |
Received Nov. 21, 2001; revised Jan. 3, 2002; accepted Jan. 7, 2002.
This work was supported by a Young Investigator Award from the National
Alliance for Research on Schizophrenia and Depression (F.A.M.),
Projects 1 (D.A.L.) and 2 (P.L., K.M.) of National Institute of Mental
Health Grant MH45156 (D.A.L.), and an endowment from the Richard King
Mellon Foundation (P.L.). We thank Dr. Takanori Hashimoto, Dianne Cruz,
and Lansha Peng for technical assistance and Dr. Gregg Stanwood for
helpful comments and discussion.
Correspondence should be addressed to Pat Levitt, Department of
Neurobiology, E1440 Biomedical Science Tower, University of Pittsburgh School of Medicine, 3500 Terrace Street, Pittsburgh, PA
15261. E-mail: plevitt+{at}pitt.edu.
| |
REFERENCES |
-
Alberts B,
Bray D,
Lewis J,
Raff M,
Roberts K,
Watson JD
(1989)
In: Molecular biology of the cell, Ed 2. New York: Garland.
-
Andreasen NC,
Rezai K,
Alliger R,
Swayze II VW,
Flaum M,
Kirchner P,
Cohen G,
O'Leary DS
(1992)
Hypofrontality in neuroleptic-naive patients and in patients with chronic schizophrenia: assessment with xenon 133 single photon emission computed tomography and the Tower of London.
Arch Gen Psychiatry
49:943-958[Abstract/Free Full Text].
-
Assies J,
Lieverse R,
Vreken P,
Wanders RJ,
Dingemans PM,
Linszen DH
(2001)
Significantly reduced docosahexaenoic and docosapentaenoic acid concentrations in erythrocyte membranes from schizophrenic patients compared with a carefully matched control group.
Biol Psychiatry
49:510-522[Web of Science][Medline].
-
Auer DP,
Wilke M,
Grabner A,
Heidenreich JO,
Bronisch T,
Wetter TC
(2001)
Reduced NAA in the thalamus, altered membrane, glial metabolism in schizophrenic patients detected by 1H-MRS, tissue segmentation.
Schizophr Res
52:87-99[Web of Science][Medline].
-
Berman KF,
Zec RF,
Weinberger DR
(1986)
Physiological dysfunction of dorsolateral prefrontal cortex in schizophrenia. II. Role of neuroleptic treatment, attention and mental effort.
Arch Gen Psychiatry
43:126-135[Abstract/Free Full Text].
-
Berman KF,
Torrey F,
Daniel DG,
Weinberger DR
(1992)
Regional cerebral blood flow in monozygotic twins discordant and concordant for schizophrenia.
Arch Gen Psychiatry
49:927-934[Abstract/Free Full Text].
-
Bernstein HG,
Grecksch G,
Becker A,
Hollt V,
Bogerts B
(1999)
Cellular changes in rat brain areas associated with neonatal hippocampal damage.
NeuroReport
10:2307-2311[Web of Science][Medline].
-
Bernstein HG,
Muller M
(1999)
The cellular localization of the L-ornithine decarboxylase/polyamine system in normal and diseased central nervous systems.
Prog Neurobiol
57:485-505[Web of Science][Medline].
-
Bertolino A,
Callicott JH,
Elman I,
Mattay VS,
Tedeschi G,
Frank JA,
Breier A,
Weinberger DR
(1998)
Regionally specific neuronal pathology in untreated patients with schizophrenia: a proton magnetic resonance spectroscopic imaging study.
Biol Psychiatry
43:641-648[Web of Science][Medline].
-
Bertolino A,
Esposito G,
Callicott JH,
Mattay VS,
Van Horn JD,
Frank JA,
Berman KF,
Weinberger DR
(2000)
Specific relationship between prefrontal neuronal N-acetylaspartate and activation of the working memory cortical network in schizophrenia.
Am J Psychiatry
157:26-33[Abstract/Free Full Text].
-
Buchsbaum MS,
Haier RJ,
Potkin SG,
Nuechterlein K,
Bracha HS,
Katz M,
Lohr J,
Wu J,
Lottenberg S,
Jerabek PA,
Trenary M,
Tafalla R,
Reynolds C,
Bunney W
(1992)
Frontrostriatal disorder of cerebral metabolism in never-medicated schizophrenics.
Arch Gen Psychiatry
49:935-942[Abstract/Free Full Text].
-
Burlina A,
Visentin B
(1965)
Ricerche di enzimopatologia negli stati schizofrenici. I. La malico-deidrogenasi del siero.
Riv Anat Patol Oncol
27:380-386[Medline].
-
Callicott JH,
Ramsey NF,
Tallent K,
Bertolino A,
Knable MB,
Coppola R,
Goldberg T,
van Gelderen P,
Mattay VS,
Frank JA,
Moonen CT,
Weinberger DR
(1998)
Functional magnetic resonance imaging brain mapping in psychiatry: methodological issues illustrated in a study of working memory in schizophrenia.
Neuropsychopharmacology
18:186-196[Web of Science][Medline].
-
Campbell DB,
North JB,
Hess E
(1999)
Tottering mouse motor dysfunction is abolished on the Purkinje cell degeneration (pcd) mutant background.
Exp Neurol
160:268-278[Web of Science][Medline].
-
Cecil KM,
Lenkinski RE,
Gur RE,
Gur RC
(1999)
Proton magnetic resonance spectroscopy in the frontal and temporal lobes of neuroleptic naive patients with schizophrenia.
Neuropsychopharmacology
20:131-140[Web of Science][Medline].
-
Darnell J,
Lodish H,
Baltimore D
(1990)
In: Molecular cell biology, Ed 2. Oxford: Scientific American Books.
-
Deicken RF,
Zhou L,
Corwin F,
Vinogradov S,
Weiner MW
(1997)
Decreased left frontal lobe N-acetylaspartate in schizophrenia.
Am J Psychiatry
154:688-690[Abstract].
-
DiAntonio A,
Haghighi AP,
Portman SL,
Lee JD,
Amaranto AM,
Goodman CS
(2001)
Ubiquitination-dependent mechanisms regulate synaptic growth and function.
Nature
412:449-452[Medline].
-
Fenton WS,
Hibbeln J,
Knable M
(2000)
Essential fatty acids, lipid membrane abnormalities, and the diagnosis and treatment of schizophrenia.
Biol Psychiatry
47:8-21[Web of Science][Medline].
-
Flayeh KA
(1988)
Permidine oxidase activity in serum of normal and schizophrenic subjects.
Clin Chem
34:401-403[Abstract/Free Full Text].
-
Gilad GM,
Gilad VH,
Casanova MF,
Casero RA
(1995)
Polyamines and their metabolizing enzymes in human frontal cortex and hippocampus: preliminary measurements in affective disorders.
Biol Psychiatry
38:227-234[Web of Science][Medline].
-
Glantz LA,
Lewis DA
(1997)
Reduction of synaptophysin immunoreactivity in the prefrontal cortex of subjects with schizophrenia.
Arch Gen Psychiatry
54:943-952[Abstract/Free Full Text].
-
Glantz LA,
Lewis DA
(2000)
Decreased dendritic spine density of prefrontal cortical pyramidal neurons in schizophrenia.
Arch Gen Psychiatry
57:65-73[Abstract/Free Full Text].
-
Goldman-Rakic PS
(1991)
Prefrontal cortical dysfunction in schizophrenia: the relevance of working memory.
In: Psychopathology and the brain (Carroll BJ,
Barrett JE,
eds), pp 1-23. New York: Raven.
-
Harrison PJ
(1999)
The neuropathology of schizophrenia. A critical review of the data and their interpretation.
Brain
122:593-624[Abstract/Free Full Text].
-
Hegde AN,
Inokuchi K,
Pei W,
Casadio A,
Ghirardi M,
Chain DG,
Martin KC,
Kandel ER,
Schwartz JH
(1997)
Ubiquitin C-terminal hydrolase is an immediate-early gene essential for long-term facilitation in Aplysia.
Cell
89:115-126[Web of Science][Medline].
-
Karson CN,
Mrak RE,
Schluterman KO,
Sturner WQ,
Sheng JG,
Griffin WS
(1999)
Alterations in synaptic proteins and their encoding mRNAs in prefrontal cortex in schizophrenia: a possible neurochemical basis for "hypofrontality."
Mol Psychiatry
4:39-45[Web of Science][Medline].
-
Kashiwagi K,
Pahk AJ,
Masuko T,
Igarashi K,
Williams K
(1997)
Block and modulation of N-methyl-D-aspartate receptors by polyamines and protons: role of amino acid residues in the transmembrane and pore-forming regions of NR1 and NR2 subunits.
Mol Pharmacol
52:701-713[Abstract/Free Full Text].
-
Kauppinen RA,
Alhonen LI
(1995)
Transgenic animals as models in the study of the neurobiological role of polyamines.
Prog Neurobiol
47:545-563[Web of Science][Medline].
-
Keshavan MS,
Stanley JA,
Pettegrew JW
(2000)
Magnetic resonance spectroscopy in schizophrenia: methodological issues and findings
 part II.
Biol Psychiatry
48:369-380[Web of Science][Medline]. -
Kim RY,
Gasser R,
Wistow GJ
(1992)
mu-Crystallin is a mammalian homologue of Agrobacterium ornithine cyclodeaminase and is expressed in human retina.
Proc Natl Acad Sci USA
89:9292-9296[Abstract/Free Full Text].
-
Lipska BK,
Jaskiw GE,
Weinberger DR
(1993)
Postpubertal emergence of hyperresponsiveness to stress and to amphetamine after neonatal excitotoxic hippocampal damage: a potential animal model of schizophrenia.
Neuropsychopharmacology
9:67-75[Web of Science][Medline].
-
Marchbanks RM,
Mulcrone J,
Whatley SA
(1995)
Aspects of oxidative metabolism in schizophrenia.
Br J Psychiatry
167:293-298[Free Full Text].
-
Mathews CK,
van Holde KE
(1989)
In: Biochemistry. Raven City, CA: Cummings.
-
Maurer I,
Zierz S,
Moller H
(2001)
Evidence for a mitochondrial oxidative phosphorylation defect in brains from patients with schizophrenia.
Schizophr Res
48:125-136[Web of Science][Medline].
-
Mirnics K,
Middleton FA,
Marquez AM,
Lewis DA,
Levitt P
(2000)
Molecular characterization of schizophrenia revealed by microarray analysis of gene expression in prefrontal cortex.
Neuron
28:53-67[Web of Science][Medline].
-
Mirnics K,
Middleton FA,
Stanwood GD,
Lewis DA,
Levitt P
(2001a)
Disease-specific changes in regulator of G-protein signaling 4 (RGS4) expression in schizophrenia.
Mol Psychiatry
6:293-301[Web of Science][Medline].
-
Mirnics K,
Middleton FA,
Lewis DA,
Levitt P
(2001b)
Analysis of complex brain disorders with gene expression microarrays: schizophrenia as a disease of the synapse.
Trends Neurosci
24:479-486[Web of Science][Medline].
-
Mulcrone J,
Whatley SA,
Ferrier IN,
Marchbanks RM
(1995)
A study of altered gene expression in frontal cortex from schizophrenic patients using differential screening.
Schizophr Res
14:203-213[Web of Science][Medline].
-
Nudo RJ,
Masterton RB
(1986)
Stimulation-induced [14C]2-deoxyglucose labeling of synaptic activity in the central auditory system.
J Comp Neurol
245:553-565[Web of Science][Medline].
-
Park S,
Holzman PS
(1992)
Schizophrenics show spatial working memory deficits.
Arch Gen Psychiatry
49:975-982[Abstract/Free Full Text].
-
Perrone-Bizzozero N,
Sower A,
Bird E,
Benowitz L,
Ivins K,
Neve R
(1996)
Levels of the growth-associated protein GAP-43 are selectively increased in association cortices in schizophrenia.
Proc Natl Acad Sci USA
93:14182-14187[Abstract/Free Full Text].
-
Pettegrew JW,
Keshavan MS,
Panchalingam K,
Strychor S,
Kaplan DB,
Tretta MG,
Allen M
(1991)
Alterations in brain high-energy phosphate and membrane phospholipid metabolism in first-episode, drug-naive schizophrenics. A pilot study of the dorsal prefrontal cortex by in vivo phosphorus 31 nuclear magnetic resonance spectroscopy.
Arch Gen Psychiatry
48:563-568[Abstract/Free Full Text].
-
Pierri JN,
Chaudry BS,
Woo TUW,
Lewis DA
(1999)
Alterations in chandelier neuron axon terminals in the prefrontal cortex of schizophrenic subjects.
Am J Psychiatry
156:1709-1719[Abstract/Free Full Text].
-
Prince JA,
Blennow K,
Gottfries CG,
Karlsson I,
Oreland L
(1999)
Mitochondrial function is differentially altered in the basal ganglia of chronic schizophrenics.
Neuropsychopharmacology
21:372-379[Web of Science][Medline].
-
Prince JA,
Yassin MS,
Oreland L
(1997a)
Neuroleptic-induced mitochondrial enzyme alterations in the rat brain.
J Pharmacol Exp Ther
280:261-267[Abstract/Free Full Text].
-
Prince JA,
Yassin MS,
Oreland L
(1997b)
Normalization of cytochrome-c oxidase activity in the rat brain by neuroleptics after chronic treatment with PCP or methamphetamine.
Neuropharmacology
36:1665-1678[Web of Science][Medline].
-
Ramchand CN,
Das I,
Gliddon A,
Hirsch SR
(1994)
Role of polyamines in the membrane pathology of schizophrenia. A study using fibroblasts from schizophrenic patients and normal controls.
Schizophr Res
13:227-234[Web of Science][Medline].
-
Selemon LD,
Goldman-Rakic PS
(1999)
The reduced neuropil hypothesis: a circuit based model of schizophrenia.
Biol Psychiatry
45:17-25[Web of Science][Medline].
-
Siegel G,
Agranoff B,
Albers RW,
Molinoff P
(1989)
In: Basic neurochemistry, Ed 4. New York: Raven.
-
Sokoloff L
(1977)
Relation between physiological function and energy metabolism in the central nervous system.
J Neurochem
29:13-26[Web of Science][Medline].
-
Stanley JA,
Pettegrew JW,
Keshavan MS
(2000)
Magnetic resonance spectroscopy in schizophrenia: methodological issues and findingspart I.
Biol Psychiatry
48:357-368[Web of Science][Medline].
-
Svinarev VI
(1987)
Serum spermidine levels of schizophrenic patients.
Zh Nevropatol Psikhiatr
87:732-734[Web of Science][Medline].
-
Thaker GK,
Carpenter WT
(2001)
Advances in schizophrenia.
Nat Med
7:667-671[Web of Science][Medline].
-
Vawter MP,
Barrett T,
Cheadle C,
Sokolov BP,
Wood III WH,
Donovan DM,
Webster M,
Freed WJ,
Becker KG
(2001)
Application of cDNA microarrays to examine gene expression differences in schizophrenia.
Brain Res Bull
55:641-650[Web of Science][Medline].
-
Volk DV,
Austin MC,
Pierri JN,
Sampson RA,
Lewis DA
(2000)
Decreased GAD67 mRNA expression in a subset of prefrontal cortical GABA neurons in schizophrenia.
Arch Gen Psychiatry
57:237-245[Abstract/Free Full Text].
-
Weinberger DR,
Berman KF,
Zec RF
(1986)
Physiological dysfunction of dorsolateral prefrontal cortex in schizophrenia. I. Regional cerebral blood flow evidence.
Arch Gen Psychiatry
43:114-124[Abstract/Free Full Text].
-
Whatley SA,
Curti D,
Marchbanks RM
(1996)
Mitochondrial involvement in schizophrenia and other functional psychoses.
Neurochem Res
21:995-1004[Web of Science][Medline].
-
Williams K
(1997)
Modulation and block of ion channels: a new biology of polyamines.
Cell Signal
9:1-13[Web of Science][Medline].
-
Williams K,
Romano C,
Dichter MA,
Molinoff PB
(1991)
Modulation of the NMDA receptor by polyamines.
Life Sci
48:469-498[Web of Science][Medline].
-
Yao JK,
Leonard S,
Reddy RD
(2000)
Membrane phospholipid abnormalities in postmortem brains from schizophrenic patients.
Schizophr Res
42:7-17[Web of Science][Medline].
Copyright © 2002 Society for Neuroscience 0270-6474/02/2272718-12$05.00/0
This article has been cited by other articles:
|
|
|
|
 
N. J. Bray
Gene Expression in the Etiology of Schizophrenia
Schizophr Bull,
May 1, 2008;
34(3):
412 - 418.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
M. J. Rossner, J. Hirrlinger, S. P. Wichert, C. Boehm, D. Newrzella, H. Hiemisch, G. Eisenhardt, C. Stuenkel, O. von Ahsen, and K.-A. Nave
Global Transcriptome Analysis of Genetically Identified Neurons in the Adult Cortex
J. Neurosci.,
September 27, 2006;
26(39):
9956 - 9966.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
K. Iwamoto and T. Kato
Gene Expression Profiling in Schizophrenia and Related Mental Disorders
Neuroscientist,
August 1, 2006;
12(4):
349 - 361.
[Abstract]
[PDF]
|
|
|
|
|
|
|
S. Akbarian, M. G. Ruehl, E. Bliven, L. A. Luiz, A. C. Peranelli, S. P. Baker, R. C. Roberts, W. E. Bunney Jr, R. C. Conley, E. G. Jones, et al.
Chromatin Alterations Associated With Down-regulated Metabolic Gene Expression in the Prefrontal Cortex of Subjects With Schizophrenia
Arch Gen Psychiatry,
August 1, 2005;
62(8):
829 - 840.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
A. Kato, N. Rouach, R. A. Nicoll, and D. S. Bredt
Activity-dependent NMDA receptor degradation mediated by retrotranslocation and ubiquitination
PNAS,
April 12, 2005;
102(15):
5600 - 5605.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
K. Iwamoto, M. Bundo, and T. Kato
Altered expression of mitochondria-related genes in postmortem brains of patients with bipolar disorder or schizophrenia, as revealed by large-scale DNA microarray analysis
Hum. Mol. Genet.,
January 15, 2005;
14(2):
241 - 253.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
T. Hashimoto, S. E. Bergen, Q. L. Nguyen, B. Xu, L. M. Monteggia, J. N. Pierri, Z. Sun, A. R. Sampson, and D. A. Lewis
Relationship of Brain-Derived Neurotrophic Factor and Its Receptor TrkB to Altered Inhibitory Prefrontal Circuitry in Schizophrenia
J. Neurosci.,
January 12, 2005;
25(2):
372 - 383.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
Y. Komatsu, A. Watakabe, T. Hashikawa, S. Tochitani, and T. Yamamori
Retinol-binding Protein Gene is Highly Expressed in Higher-order Association Areas of the Primate Neocortex
Cereb Cortex,
January 1, 2005;
15(1):
96 - 108.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
J. Zhang, A. Moseley, A. G. Jegga, A. Gupta, D. P. Witte, M. Sartor, M. Medvedovic, S. S. Williams, C. Ley-Ebert, L. M. Coolen, et al.
Neural system-enriched gene expression: relationship to biological pathways and neurological diseases
Physiol Genomics,
July 8, 2004;
18(2):
167 - 183.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
J. Z. Li, M. P. Vawter, D. M. Walsh, H. Tomita, S. J. Evans, P. V. Choudary, J. F. Lopez, A. Avelar, V. Shokoohi, T. Chung, et al.
Systematic changes in gene expression in postmortem human brains associated with tissue pH and terminal medical conditions
Hum. Mol. Genet.,
March 15, 2004;
13(6):
609 - 616.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
C. Konradi, M. Eaton, M. L. MacDonald, J. Walsh, F. M. Benes, and S. Heckers
Molecular Evidence for Mitochondrial Dysfunction in Bipolar Disorder
Arch Gen Psychiatry,
March 1, 2004;
61(3):
300 - 308.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
N. Mah, A. Thelin, T. Lu, S. Nikolaus, T. Kuhbacher, Y. Gurbuz, H. Eickhoff, G. Kloppel, H. Lehrach, B. Mellgard, et al.
A comparison of oligonucleotide and cDNA-based microarray systems
Physiol Genomics,
February 13, 2004;
16(3):
361 - 370.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
T. Hashimoto, D. W. Volk, S. M. Eggan, K. Mirnics, J. N. Pierri, Z. Sun, A. R. Sampson, and D. A. Lewis
Gene Expression Deficits in a Subclass of GABA Neurons in the Prefrontal Cortex of Subjects with Schizophrenia
J. Neurosci.,
July 16, 2003;
23(15):
6315 - 6326.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
W. E. Bunney, B. G. Bunney, M. P. Vawter, H. Tomita, J. Li, S. J. Evans, P. V. Choudary, R. M. Myers, E. G. Jones, S. J. Watson, et al.
Microarray Technology: A Review of New Strategies to Discover Candidate Vulnerability Genes in Psychiatric Disorders
Am J Psychiatry,
April 1, 2003;
160(4):
657 - 666.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
F. M. Benes, J. Walsh, S. Bhattacharyya, A. Sheth, and S. Berretta
DNA Fragmentation Decreased in Schizophrenia but Not Bipolar Disorder
Arch Gen Psychiatry,
April 1, 2003;
60(4):
359 - 364.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
R. C. Elliott, M. F. Miles, and D. H. Lowenstein
Overlapping Microarray Profiles of Dentate Gyrus Gene Expression during Development- and Epilepsy-Associated Neurogenesis and Axon Outgrowth
J. Neurosci.,
March 15, 2003;
23(6):
2218 - 2227.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
TOP
ABSTRACT
INTRODUCTION
