hand2 and dlx3b/4b/5a have opposing roles in regulating gsc and nkx3.2. (A-T) Lateral views (left; anterior leftwards, dorsal upwards) taken from single confocal sections of RNA in situs and reconstructed orthogonal sections (right; medial leftwards, dorsal upwards) through the first arch joint region of 48 hpf fish. Markers are indicated on the left panel of each row, and treatments are indicated above each column. nkx3.2 expression is often reduced by (J) dlx3b;4b;5a-MO injection (80% penetrance), expanded in (K) uninjected hand2S6, but reduced in (L) hand2S6;dlx3b;4b;5a-MO. (N) In wild-type fish injected with dlx3b;4b;5a-MO, the dorsal and ventral gsc domains are occasionally (7% penetrance) found fused together (asterisk), medial to (F) nkx3.2 expression. (O) In uninjected hand2S6 fish, ventral first arch gsc is lost, but some dorsal expression remains (arrowhead). (P) In hand2S6;dlx3b;4b;5a-MO, ventral gsc is defective in arch one, and sometimes reduced (45% penetrance) in arch two, whereas ectopic gsc is seen attached to dorsal arch one expression (55% penetrance, arrow), medial to nkx3.2. Scale bar: 100 μm.
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