Fig. 1

vgll2a expression in the developing zebrafish. In situ hybridization (ISH) using a vgll2a probe at 2 somites (A), 17 somites (B, C), 22 hpf (D, E), 30 hpf (F–I), 40 hpf (J), 48 hpf (K) and 64 hpf (L) stages showing lateral (A, B, D, F, J, K, L), dorsal (C, E) or ventral (inset, L) views. 4 µm plastic sections (G, H, I) of 30 hpf embryos sectioned in planes shown in panel F. vgll2a is first detected in the developing somites (black arrows, A and B) of zebrafish at the 2-somite stage (A). By 17 somites (B,C), vgll2a is also expressed at low levels in a population of endodermal cells (black arrow, C) as they evaginate to form the first pharyngeal pouch. At 22 hpf, lateral (D) and dorsal (E) views reveal that vgll2a is also expressed in the lateral pharyngeal endoderm (black arrows, D, E) as the pouches continue to form, as well as in the pharyngeal ectoderm (white arrow, E) and ventral forebrain (black arrowhead, D). At 30 hpf, expression of vgll2a is also apparent in the region of the developing trigeminal ganglion (black arrow, F) Dashed lines indicate plane of section in G–I. 4 µm plastic sections of 30 hpf embryos (G, H, I) reveal that vgll2a expression, in addition to being expressed within a discrete population of cells within the ventral forebrain (black arrowhead, G) and prominently in the pharyngeal pouch endoderm (H, and black arrow in higher magnification view of boxed region in, I), is also expressed in the overlying pharyngeal ectoderm (white arrow, I). From 30 to 48 hpf (F–K), vgll2a continues to be expressed in the endodermal pouches (black arrow, J,K), somite expression fades, and forebrain expression expands. At 40 hpf and later stages, vgll2a is expressed in the stomodeum, the presumptive mouth (white arrow, J, K, L). By 48 hpf (K), it begins to be expressed in sites of myogenesis other than the somites, including the fin bud (fb) and cephalic musculature and is also apparent in the notochord (black arrowhead). Cranial muscle expression is more apparent by 64 hpf (L), at which time vgll2a becomes reactivated in the somitic muscle. Anterior is to the left in all panels. am, adductor mandibulae; do, dilator operculi; hh, hyohyoideus; ih, interhyoideus; ima, intermandibularis anterior; imp, intermandibularis posterior; io, inferior oblique; lap, levator arcus palatini; sh, sternohyoideus; so, superior oblique; sr, superior rectus.