RT Journal Article
SR Electronic
T1 Abnormalities in the Climbing Fiber-Purkinje Cell Circuitry Contribute to Neuronal Dysfunction in <em>ATXN1</em>[<em>82Q</em>] Mice
JF The Journal of Neuroscience
JO J. Neurosci.
FD Society for Neuroscience
SP 12778
OP 12789
DO 10.1523/JNEUROSCI.2579-11.2011
VO 31
IS 36
A1 Justin A. Barnes
A1 Blake A. Ebner
A1 Lisa A. Duvick
A1 Wangcai Gao
A1 Gang Chen
A1 Harry T. Orr
A1 Timothy J. Ebner
YR 2011
UL http://www.jneurosci.org/content/31/36/12778.abstract
AB One fundamental unanswered question in the field of polyglutamine diseases concerns the pathophysiology of neuronal dysfunction. Is there dysfunction in a specific neuronal population or circuit initially that contributes the onset of behavioral abnormalities? This study used a systems-level approach to investigate the functional integrity of the excitatory cerebellar cortical circuitry in vivo from several transgenic ATXN1 mouse lines. We tested the hypotheses that there are functional climbing fiber (CF)–Purkinje cell (PC) and parallel fiber (PF)–PC circuit abnormalities using flavoprotein autofluorescence optical imaging and extracellular field potential recordings. In early-symptomatic and symptomatic animals expressing ATXN1[82Q], there is a marked reduction in PC responsiveness to CF activation. Immunostaining of vesicular glutamate transporter type 2 demonstrated a decrement in CF extension on PC dendrites in symptomatic ATXN1[82Q] mice. In contrast, responses to PF stimulation were relatively normal. Importantly, the deficits in CF–PC synaptic transmission required expression of pathogenic ataxin-1 (ATXN1[82Q]) and for its entrance into the nucleus of PCs. Loss of endogenous mouse Atxn1 had no discernible effects. Furthermore, the abnormalities in CF–PC synaptic transmission were ameliorated when mutant transgene expression was prevented during postnatal cerebellar development. The results demonstrate the preferential susceptibility of the CF–PC circuit to the effects of ATXN1[82Q]. Further, this deficit likely contributes to the abnormal motor phenotype of ATXN1[82Q] mice. For polyglutamine diseases generally, the findings support a model whereby specific neuronal circuits suffer insults that alter function before cell death.