Figure 7. The putative networks governed by Hand2 in the branchial arch.

(A,B) Schematic presentation of the transcription factor expression that is affected by altered Hand2 expression in the neural crest-derived cells at E11.5 (A) and E12.5 (B). The red arrows indicate upregulation, and the blue arrow indicates downregulation in the Hand2^NC mutants compared with the wild-type. The nested expression of Hand2 in the mandibular process regulates jaw patterning by controlling the homeobox transcription factors. An asterisk indicates a duplicate. (C) Model of the putative transcriptional regulation of mandibular identity by Hand2. Dlx5 and Dlx6 activate Hand2 expression distally¹⁵,¹⁶,³³. Hand2 induces and/or maintains Group A and represses Group B homeobox transcription factors in the mandibular process. Presumably, the Group A homeobox transcription factors are involved in lower jaw identity, whereas the Group B homeobox transcription factors promote upper jaw development. The solid lines indicate direct interactions, whereas the dashed lines indicate genetic interactions.