Article Figures & Data
Figures
- Figure 1.
The development of the Tlx mutant LGE is compromised. A, C, At E12.5 (A) and E14.5 (C), Ki67, which marks cells in all stages of the cell cycle, is expressed in the LGE VZ and SVZ. B, At E12.5, there appears to be no significant differences between the Tlx mutant and wild-type LGE with respect to size as well as Ki67 expression. D, However, at E14.5, there is both an obvious reduction in size and the number of Ki67-expressing cells in the LGE. E-G, Also, after a 2 hr BrdU pulse, fewer BrdU-positive cells are detected in the E14.5 Tlx mutant LGE, particularly in the SVZ. E, We counted BrdU-positive cells in the LGE using four square-shaped bins placed adjacent to each other along the ventriculo-pial axis of the ventral LGE. The first bin extended from the ventricular lumen to the end of the ventricular zone in a wild-type LGE. G, Whereas the number of BrdU-positive cells in the first bin was not significantly different between wild-type and Tlx mutant embryos, the number of BrdU-positive cells in the three other bins were. KO, Knock-out; Se, septum; Stm, striatum. *p ≤ 0.01; Student's unpaired t test between wild-type and Tlx mutants.
- Figure 2.
GSH2 expression in the E12.5 and E14.5 Tlx mutant LGE. A, C, GSH2 is normally expressed in a gradient throughout the LGE VZ; the highest expression is detected in the most dorsal part of the LGE (indicated by arrows), and the lowest expression is detected in the sulcus between the LGE and MGE. B, D, In Tlx mutants, the level of GSH2 expression is more uniform; high levels of GSH2 are detected in a broader region of the LGE VZ (indicated by arrows). In addition, the “thickness” of the expression domain in the VZ is reduced, indicating that the number of precursor cells expressing GSH2 along the ventricular-pial axis is reduced. Stm, Striatum; KO, knock-out.
- Figure 3.
Striatal defects in E18.5 Tlx mutant and Gsh2/Tlx double-mutant brains. Staining for the striatal markers DARPP-32 (A-C) and calbindin (D-F) shows that the Tlx mutant striatum (Stm; B, E) is smaller than that of a wild-type (A, D), and the Gsh2/Tlx double-mutant striatum (C, F) is even smaller. Although the striatum is smaller in each of these mutants, significant DARPP-32 expression is detected in the Tlx (B) and Gsh2/Tlx mutant (C). Furthermore, calbindin expression appears to be upregulated in the Tlx (E) and Gsh2/Tlx mutant striata (F). G, H, There appears to be no significant difference in the number of Er81-positive olfactory bulb interneurons in the granule cell (GCL) and mitral and glomerular (GL) layers in the Tlx mutant versus wild-type adult brain. ac, Anterior commissure; lv, lateral ventricle; KO, knock-out.
- Figure 4.
Altered molecular identity in the E14.5 Tlx, Gsh2, and Gsh2/Tlx mutant LGE. A, In the E14.5 wild-type telencephalon, Er81 is expressed in the dorsal LGE SVZ (arrows). In Tlx mutants (B), the Er81 expression domain is expanded both dorsally (Stenman et al., 2003b) and ventrally (arrows). Gsh2 mutants (C) and Gsh2/Tlx double mutants (D) lack SVZ expression of Er81 (C, D, asterisks). Note that Er81 expression in the Gsh2 mutants and Gsh2/Tlx double mutants is confined to the VZ. E, In the wild type, ISL1 expression is detected in the ventral LGE SVZ and in differentiating cells of the developing striatum (Stm). In Tlx mutants (F), the ISL1 expression is weaker and the expression domain is noticably reduced in size at this stage. G, Also, in Gsh2 mutants, fewer ISL1-positive cells are detected and even fewer in the Gsh2/Tlx double mutants (H). KO, Knock-out.
- Figure 5.
NKX6.2 expression in wild-type and Tlx mutant embryos. A, At E12.5, NKX6.2 is expressed in the sulcus between the LGE and MGE. A few scattered cells can also be detected in the LGE and MGE VZ right next to the domain of high NKX6.2 expression. B, In the Tlx mutant, NKX6.2 is ectopically expressed in the ventral half of the LGE. C, Also at E14.5, NKX6.2 expression is detected in the VZ between the LGE and MGE. D, In E14.5 Tlx mutants, the NKX6.2 expression domain in the mutants appears rather small; however, considering that the LGE is smaller in the mutant at this stage, the domain is relatively larger. In addition, NKX6.2 is ectopically expressed in scattered cells throughout much of the LGE VZ (compare insets in C and D). KO, Knock-out; Stm, striatum.
- Figure 6.
Patterning defects in Gsh2 mutants and Gsh2/Tlx double mutants. A, At E12.5, NKX6.2 is expressed in the sulcus between the LGE and MGE. B, In Gsh2 mutants, a number of scattered cells expressing NKX6.2 ectopically are detected in the ventral most part of the LGE. Note also that the size of the mutant LGE is smaller than the wild-type LGE. C, In the Gsh2/Tlx double mutants, as in the Tlx mutants (Fig. 2B), NKX6.2 is ectopically expressed in the ventral half of the LGE. D, High PAX6 expression normally wraps around the pallio-LGE angle and stops in the dorsalmost portion of the LGE. In addition, a stream of PAX6-positive cells emanates from the ventralmost region of the PAX6 VZ expression domain down to the mantle zone (arrows). E, In Gsh2 mutants, PAX6 is ectopically expressed in the dorsal half of the LGE. Interestingly, the number of PAX6-positive cells in the mantle zone (arrows) is significantly reduced in these mutants. F, PAX6 is ectopically expressed also in the dorsal half of the Gsh2/Tlx double-mutant LGE. Surprisingly, in the Gsh2/Tlx double mutants, there appears to be a considerable number of PAX6-positive cells in the mantle zone (arrows). Note also that the ectopic expression of PAX6 and NKX6.2 in the double-mutant LGE leaves only a small domain of the ventral LGE correctly patterned (C, F). G, NKX6.2 expression at E14.5 in the wild-type telencephalon. H, Scattered cells throughout the E14.5 Gsh2 mutant LGE, which is significantly reduced in size, express NKX6.2 ectopically (inset). I, Interestingly, in the Gsh2/Tlx double mutant, NKX6.2 is extopically expressed at high levels throughout the LGE VZ up to the LGE-pallium angle. J, PAX6 is expressed in the pallium at E14.5. K, In Gsh2 mutants, a recovery is occurring by E14.5, and PAX6 expression is primarily normalized. L, This recovery also occurs in Gsh2/Tlx double mutants. Note that the expression domains of PAX6 and NKX6.2 nearly abut in the double mutants. (I, L). KO, Knockout; Stm, striatum.
- Figure 7.
Genetic regulation of ventral pallial identity. A, Dbx1 is a marker of the ventral pallium. B, In the Gsh2 mutant, Dbx1 is ectopically expressed in the LGE. C, This is also the case in the Gsh2/Tlx double mutant; however, the number of cells expressing Dbx1 is drastically reduced. Note that, although Dbx1 is expressed in the LGE-cortex angle in the wild type, this area lacks expression of Dbx1 in the Gsh2 mutant and Gsh2/Tlx double-mutant telencephalon. Another marker of the ventral pallium, SFRP2, is expressed in the LGE-cortex angle at E12.5 (arrow in D). At this stage, the location of the SFRP2 expression domain is shifted ventrally in Gsh2 mutants (open arrow) compared with its normal position (arrow). F, In the Gsh2/Tlx double mutant, SFRP2 expression is missing. G, Also at E14.5, SFRP2 expression is detected in the LGE-cortex angle (arrow in G). H, After the recovery, which is occurring in Gsh2 mutants by E14.5, SFRP2 expression is undistinguishable from the wild type. I, However, in a Gsh2/Tlx double mutant, SFRP2 expression is still missing. KO, Knock-out.
- Figure 8.
Some aspects of ventral pallial identity are retained even in the absence of Tlx and Gsh2. A, B, In a wild type, Tbr1 (A) and Lhx2 (C) are expressed in the entire pallial SVZ and the ventral pallium SVZ, respectively. B, In Gsh2/Tlx double mutants, SVZ expression of Tbr1 is expanded into the LGE, showing that not only the VZ adopts a pallial identity. D, In addition, Lhx2 expression in the SVZ is shifted into the LGE, showing that, despite the lack of SFRP2 and Dbx1 in the VZ, aspects of ventral pallial identity are still retained in the double mutants. Filled arrows mark the pallio-subpallial boundary in wild types. Open arrows mark the ventral shift of this boundary in the double mutants. KO, Knock-out.
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