Sp8 and Sp9 coordinately promote D2-type medium spiny neuron production by activating Six3 expression [ChIP-Seq]

D1- and D2-type medium spiny neurons (MSNs) are the principal projection neurons in the striatum, including in the dorsal striatum (caudate nucleus and putamen) and ventral striatum (nucleus accumbens and olfactory tubercle) that are generated by the lateral ganglionic eminence (LGE). Using conditional deletion, we show that mice lacking the Sp8 and Sp9 transcription factors (TFs) selectively have a severe reduction in D2 MSNs due to reduced neurogenesis in the LGE. Sp8/9 together drive expression of the Six3 TF in a spatial restricted domain of the LGE subventricular zone. Conditional deletion of Six3 also prevents the formation of most D2 MSNs, phenocopying the Sp8/9 loss of function. Finally, ChIP-Seq reveals that SP9 directly binds to the promoter and a putative enhancer of Six3. This study provides evidence for components of a transcription pathway, in a regionally restricted LGE domain, that selectively drives the generation of D2 MSNs. We examined Sp9 binding (TF ChIP-seq) from basal ganglionic eminence in E13.5 and E16.5 wild type mice.