Figure 1

GABA progenitor domains in the chick thalamus. Progenitor territories with a GABAergic fate in the thalamus and pTh are visualized by expression of Ascl1 and Lhx5 and are present on both sides of the regional organizer zli, labeled by Shh expression. Thalamic progenitors positioned further away from the zli acquire a glutamatergic fate and express Neurog1 and Lhx9 (A). Schematic drawing illustrating the position of prethalamic (pTh), rostral thalamic (rTh) and caudal thalamic (cTh) progenitor domains in lateral and coronal views of the developing chick brain (B). Helt, Tal1 and Sox14 are expressed in rTh progenitors and precursors. Their expression overlaps with GABAergic markers Gad1 and Reelin. From the fifth day of incubation (E5), rTh GABA derivatives express the interneuron subtype marker and calcium binding protein Calretinin (Calb2) (C). E6 rTh neurons can be visualized by immunodetection of the GABA-synthesizing enzymes GAD65/67. The calcium binding protein Calb2 is present and co-expressed with the transcription factor Sox14 in a subset of rTh neurons (D). Position of rTh progenitors in the perirotundic area of the chick thalamus by day E10 of embryonic development. The Calb2-expressing neurons appear to segregate from Npy-expressing neurons within the perirotundic area and may represent two subtypes within the rTh pool. Both cell groups are labeled by the panGABAergic marker Gad1 (E). Scale bars: 100 μm.