Figure 5: Fate mapping of Nkx2.2 progenitors in the dLGN excludes GABA interneurons.

Nkx2.2^cre/+;R26-LSL-tdTomato conditional reporter expression was used to trace the fate of Nkx2.2 progenitors in the thalamus. (a) IHC in the E12.5 brain of a Sox14^Gfp/+ embryo shows Nkx2.2 in progenitors of p3 and in the pTh-R domain of p2, which together define the presumptive GABA-rich vLGN and IGL territory, respectively (see also b). Nkx2.2 progenitors are not present in p1. Sequential activation of Gata2 and Sox14 defines a subset of Nkx2.2 progenitors in the pTh-R domain. Scale bar, 100 μm. (b) Adult brains (P30) of Nkx2.2^cre/+;R26-LSL-tdTomato mice reveal the known contribution of Nkx2.2 progenitors to the vLGN and IGL. There is virtually no co-expression of GABA and tdTomato in the dLGN (white arrowheads in insets 1 and 2; out of 586 GABA⁺ dLGN cells counted, 576 are negative for tdTomato and only 10 may have weak or unclassifiable tdTomato expression; N=3 brains). Scale bars are 100 μm in the low-magnification image and 1 μm in insets. (c) The fate of Nkx2.2 progenitors in the dLGN is largely non-neuronal, as indicated by weak to no staining for the pan-neuronal marker Tuj1 in tdTomato⁺ cells of Nkx2.2^cre/+;R26-LSL-tdTomato mice (white arrowheads). A representative GABAergic, tdTomato-negative cell is also shown (yellow arrow). Scale bar, 1 μm.