Upon Helt downregulation and before Sox14 induction, this population also activates expression Tal1 ( Figures 1C, 1E, and 1F). Colabeling of the embryonic day (E) 12.5 diencephalon with Dlx2, Sox14, and Gad1 indicates that GABA-synthesizing neurons arise from either the Dlx2-positive population or Sox14-positive population ( Figures 1D and 1G). We therefore conclude that all Dlx2-negative GABAergic neurons in the diencephalon arise from the Helt-, Tal1-, and Sox14-positive population and that Dlx2 expression or lack of it defines two alternative GABAergic subtypes. The onset of Sox14 expression correlates with cell-cycle exit in cells that have already initiated

transcription of the Gad1 gene ( Figures 1D–1F). Sox14 expression is maintained during embryogenesis but is progressively lost within the first 3 weeks after birth PF-02341066 cell line (data not shown). By contrast, Helt is only Alectinib supplier transiently expressed from the onset of neurogenesis up to E14.5 and

Tal1 is expressed in intermediate progenitors but not in the most differentiated stages ( Figures 1A–1C and 1F). Therefore, to further study the development and function of this diencephalic neuronal population, we took advantage of a knockout (KO) mouse in which the Sox14 coding sequence is replaced by the cDNA for eGfp by homologous recombination ( Crone et al., 2008). The heterozygote Sox14gfp/+ is virtually a wild-type (WT) Carnitine dehydrogenase animal and is therefore a useful tool to study Sox14-expressing neurons during their normal development. From the onset of neurogenesis, green fluorescent protein (GFP)-expressing cells are visible in two stripes extending transversely across the diencephalon, coinciding with the r-Th and the caudal pretectum ( Figures 2A and 2B).

In the hypothalamic region, GFP is visible in the future ventromedial hypothalamus (VMH) and in the medial preoptic area (MPO) ( Figures 2B and 2C and data not shown). Several differences in marker expression between the r-Th/pretectal domain and the hypothalamic domain of Sox14 expression, including the Helt and Tal1 transcription factors and the neurotransmitter markers Gad1 and Vglut2, suggest that the hypothalamic Sox14-positive domain follows an altogether different developmental program and was not considered further. To assess the fate of pretectal and thalamic Sox14-positive cells, we followed their location during nucleogenesis from stage E14.5 to postnatal day (P) 2. By E16.5, Sox14 cells form well-defined clusters in the pretectum, thalamus, and prethalamus. The most rostrodorsal cluster of Sox14 cells is located next to the lateral habenula (LHa, labeled by Prokr2 expression) ( Figures 2C and 2D and see Figure S1 available online). This cluster extends in a caudoventral direction along the thalamus-pretectum border to form the nucleus posterior limitans (PLi).