Fig. 7.

Model for Sobp interactions during craniofacial development. (A) Sobp expression in two ectodermal domains (PPE and EP) directly or indirectly induces epidermal genes (krt12.4), represses neural plate genes (sox2) and represses the Six1+Eya1 transcriptional activation (asterisk) in the PPE. Sobp effects outside the PPE are likely independent of Six1. Repression of the transcriptional activation of Six1+Eya1 target genes (asterisk) is likely achieved by higher levels of Sobp and lower levels of Six1, and the additional expression of the known Six1 co-repressors (e.g. Groucho/Tle) in the anterior PPE. Conversely, in the posterior PPE, lower levels of Sobp, higher levels of Six1 and lower/no Groucho/Tle expression leads to transcriptional activation. Eya1 is co-expressed with Six1 in this domain. A, anterior; EP, epidermis; L, lateral; M, medial; NP, neural plate; NC, neural crest; P, posterior; PPE, pre-placodal ectoderm. (B) Sobp expression in the medial wall of the otic vesicle is higher in the dorsal region, a domain where Dach co-repressors are also expressed. This expression pattern leads to repression of the transcriptional activation of Six1+Eya1 target genes (asterisk), thus allowing expression of dorsal otic genes (e.g. Dlx5). Ventrally, Sobp induces expression of Pax2 independent of Six1. Six1 and Eya1 have overlapping expression. D, dorsal; L, lateral; M, medial; V, ventral.