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Fig. 1 Conserved expression of tfap2a during otic neurogenesis.
All images show cross-sections of the otic placode or vesicle in wild type zebrafish embryos (A-J) or chick embryos (L-Q) with a dorsal up and medial to the left. (A, B) At 14 hpf (10 somites) pax2a (red) marks the precursor cells in the emerging otic placode that are co-labeled with tfap2a (blue). (C-H) Cross-sections through the widest part of the neurogenic domain of the otic vesicle, just posterior to the utricular macula. The outer and inner edges of the otic vesicle are outlined. Patterns of ngn1 or tfap2a are shown at the indicated times. tfap2a is expressed in the ventrolateral part of the otic vesicle, which partially overlaps the domain of ngn1 expression. (I-J) Cross-sections passing through the utricular macula of specimens co-stained for Isl1 (red) and tfap2a (blue) at 48 hpf. Expression of tfap2a is not detected in the floor of the otic vesicle or in the mature SAG neurons at this time. (K) Schematic summary of SAG development in zebrafish, including regional markers. Neuroblasts are specified and delaminate from the otic vesicle (light purple) adjacent to nascent sensory epithelia (green). Recently delaminated neuroblasts migrate towards hindbrain and continue to proliferate, forming the transit-amplifying pool (blue). Neuroblasts then stop dividing and differentiate into mature neurons (red). Relevant genes expressed in each domain are indicated. Expression of tfap2a (dark purple) overlaps the neurogenic domain, as well as the domain of bmp7a expression. Note that all of the tissues indicated express Fgf-target genes (etv5b and spry4) and transducers of Bmp (smad1 and smad5), but transit amplifying SAG precursors show specific upregulation of smad1 and smad5 [37]. (L-Q) Cross-sections through the otic vesicle of chick embryos at days 3 and 4 (E3 and E4). The sensory region is labeled with Jagged-1 (green). Tfap2a (red) is expressed in the ventrolateral otic domain in chick embryos similar to the pattern observed in zebrafish.