Expression of the actinin gene family at 24-48 hpf. Expression of the actinins by whole mount in situ hybridization reveals distinct patterns for most genes. A-J: Lateral whole mount views with insets showing higher magnification dorsal or lateral views of somite gene expression; insets are magnified lateral (C,Gb,I,J), dorsal (A,B,D,E,Ga), or anterioventral (H) views); A′-J′: Transverse sections of axial gene expression taken at level indicated by blue lines in A-J. A,A′: Expression of slow-specific marker stnnc at 24 hpf. Expression was observed in slow muscle fibers including muscle pioneer cells (arrow) and in peripheral slow muscle sheath. B,B′: Expression of fast-specific marker myhz2 at 24 hpf. Expression is seen in most of the somite but no expression is seen in the muscle pioneer cells (arrow). C,C′: Expression of actn2 at 24 hpf. Expression is seen in the heart (arrowhead) and in the slow muscle pioneers (arrows). D,D′,E,E′: Expression of actn3a (D,D′) and actn3b (E,E′) at 24 hpf. Both actn3a and actn3b are widely expressed in the somite. Expression is also seen in the slow muscle pioneer cells (arrows). F,F′: Expression of actn1 at 36 hpf. Expression was observed in the skin (arrow), notochord (arrowhead), and generally expressed in the somite. Expression was not observed in the neural tube (nt) or other components of the CNS. G,G′: Expression of actn4 at 36 hpf. Expression is seen in the notochord (arrows) as well as the developing gut (arrowhead). H,H′: Expression of actn2 at 48 hpf. Expression is seen in the heart (arrowheads) but is no longer observed in the slow muscle fibers of the myotome (arrow). H″: Expression of stnnc at 48 hpf. Expression can be seen in the peripheral sheath of slow muscle fibers (arrow). I,I′,J,J′: Expression of actn3a (I,I′) and actn3b (J,J′) at 48 hpf. Both actn3a and actn3b are broadly expressed in most or all of the myotome muscle fibers.
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