Fig. 8. Model of the genetic pathway regulating development of the anterior and posterior pharyngeal arches in zebrafish. (A) edn1 expression in 27 hpf wild-type embryo and (B) schematic drawing of the tbx1 pathway in an arch primordium (dark blue, pharyngeal arch epithelium and mesodermal core; light blue, neural crest cells). Outlined in black is the hyoid arch, exemplifying the distribution of edn1- and tbx1-positive cells within a developing arch. (C) Genetic pathway regulating development of the anterior and posterior arches and zebrafish mutants analyzed in this study with the expression of tbx1, edn1 and hand2 in these mutants. Dash indicates `no data'. Mandibular (p1) and hyoid (p2) arches: tbx1 regulates edn1 within the arch epithelium and the mesodermal core. Within these arches, edn1 is also possibly regulated independently by another gene, probably an Fgf. edn1 in turn regulates the expression of hand2 in the neural crest-derived cells surrounding the mesodermal core of the arch. In posterior arches (p3-7), tbx1 is likely to be the major regulator of edn1. Downstream of edn1, hand2 expression is likely to be controlled by edn1, as well as by tbx1 via an as yet unknown signaling molecule (`?').

Return to article