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. Author manuscript; available in PMC: 2009 Apr 15.
Published in final edited form as: Nat Rev Neurosci. 2008 Sep;9(9):678–685. doi: 10.1038/nrn2463

Figure 4. Key genetic pathways that interact to form and pattern the early telencephalon.

Figure 4

Factors that act early to establish broad telencephalic regions are shown in blue. Sonic hedgehog (SHH) ventralizes the telencephalon by antagonizing the dorsalizing effect of GLI3. By repressing Gli3, SHH, together with forkhead box G1 (FoxG1), activates fibroblast growth factor (FGF) expression. FGF might feedback and promote Foxg1 expression (dotted arrow). FoxG1 and FGF signalling are necessary for forming all regions of the telencephalon (shown in green), except for the dorsomedial region (shown in orange). Downstream transcription factors, such as GSH2 and NKX2.1, then form specific subdivisions. In the dorsal telencephalon, GLI3’s promotion of the expression of bone morphogenetic proteins (BMPs) and Wingless/Int proteins (WNTs) is required for EMX-gene expression. The products of the EMx genes, along with PAX6 and LHX2, further subdivide the dorsal telencephalon. LGE, lateral ganglionic eminence; MGE, medial ganglionic eminence.