Expression of Meis and Pbx genes and their protein products in the developing telencephalon: implications for regional differentiation.

The Meis and Pbx genes encode for homeodomain proteins of the TALE class and have been shown to act as co-factors for other homeodomain transcription factors (Mann and Affolter, 1998. Curr. Opin. Genet. Dev. 8, 423-429). We have studied the expression of these genes in the mouse telencephalon and found that Meis1 and Meis2 display region-specific patterns of expression from embryonic day (E)10.5 until birth, defining distinct subterritories in the developing telencephalon. The expression of the Meis genes and their proteins is highest in the subventricular zone (SVZ) and mantle regions of the ventral telencephalon. Compared to the Meis genes, Pbx genes show a broader expression within the telencephalon. However, as is the case in Drosophila (Rieckhof et al., 1997. Cell 91, 171-183; Kurrant et al., 1998. Development 125, 1037-1048; Pai et al., 1998. Genes Dev. 12, 435-446), nuclear localized PBX proteins were found to correlate highly with Meis expression. In addition, DLX proteins co-localize with nuclear PBX in distinct regions of the ventral telencephalon.