Fig. 4

(Overleaf) Muscle-specific actinins are differentially expressed in axial and craniofacial musculature at 96 hpf. A-C: Lateral whole-mount views. Inset in Aa: Transverse section at the posterior gut level; insets in Ab, B, and C are higher magnification lateral views of somite expression. A′-C′: Higher magnification lateral views of craniofacial expression from A-C. D: Camera lucida representation identifying muscles of zebrafish at 96 hpf (abbreviations listed in Table 1). E-I, F′-H′: Ventral views of craniofacial expression, with E-I having a ventral focal plane and F′-H′ a dorsal focal plane. Jaw structures and sternohyoideus muscles have been removed in G′ for visibility of more dorsal muscles. J-N: Transverse sections at the level of the heart. A,A′: Expression of actn2 at 96 hpf. Expression is seen in the heart (arrow) as well as the lateralis superficialis (white arrowhead) and inferior obliquus (black arrowhead). In the cranial musculature, strong actn2 expression was seen in lap muscles (green arrowhead). Inset AB shows broad expression of stnnc at 96 hpf in the slow fibers of the myotome. B,B′: Expression of actn3a at 96 hpf. Expression was seen in the axial musculature (white arrowhead, superficial expression). Expression was also seen in cranial and pharyngeal muscles and strong expression is seen in the sh (arrowhead). C,C′: Expression of actn3b at 96 hpf. Expression was seen in the axial musculature. Weak expression was seen in the sh (arrowhead). D: Craniofacial muscle groups are colored to demarcate pharyngeal arches of origin: red, mandibular arch (pharyngeal arch 1, P1); green, hyoid arch (P2); yellow, branchial arches 1-5 (P3-P7); purple, extraocular/cranial muscle; pink, somite-derived muscle; orange, cardiac muscle. E: stnnc was expressed uniformly in most cranial and pharyngeal muscle. Expression was light in sh muscles (white arrowhead). F-H: Expression of the muscle-specific actinins in sh muscles was variable between homologs. actn2 was weakly expressed in the sh (arrowhead, F), actn3a was very strongly expressed (arrowhead, G), and actn3b was moderately expressed (arrowhead, H). I: myhz2 was expressed strongly in sh muscles (arrowhead). J: actn2 expression was weak in tv and dpw muscles (white and green arrowheads, respectively) compared to its strong expression in lap muscles (black arrowhead). K,L: actn3a (K) was weakly expressed in tv (white arrowheads), dpw (green arrowheads), and lap (black arrowheads) muscle pairs. actn3b (L) expression was high in all pharyngeal muscles. M-Q: stnnc was expressed in the periphery of the sh (arrowhead, M). myhz2 was expressed in the center of the sh (arrowhead, N). actn2 was expressed in the periphery of the sh (arrowhead, O). actn3a was expressed in the center of the sh (arrowhead, P). actn3b was expressed in the center of the sh (arrowhead, Q).