Expression of the major muscle laminin genes (lama2, lamb2, and lamc1) in zebrafish during development. A–C: Lateral whole-mount view of the 16–somite stage showing lama2 (A), lamb2 (B), and lamc1 (C) expression, with corresponding transverse (A′–C′) and sagittal (A″–C″) sections in the developing myotome. D–F′: Lateral whole-mount view of larvae staged 24 hr post-fertilization (hpf) is shown for lama2 (D, D′), lamb2 (E, E′), and lamc1 (F, F′) with corresponding transverse (D′–F′) sections through the trunk musculature. All genes are expressed in the slow and fast compartments of the myotome. G–I″: Lateral view of larvae staged at 48 hpf is shown for lama2 (G, G″), lamb2 (H, H″), and lamc1 (I, I″) with corresponding transverse (G′–I′) sections through the trunk musculature. All genes are expressed in the slow and fast compartments of the myotome with additional expression in neuronal tissues. J–O′: Larvae staged at 72 hpf are shown in lateral (lama2 [J, J″], lamb2 [K, K″], and lamc1 [L, L″]) and dorsal (lama2 [M], lamb2 [N], and lamc1 [O]) view with corresponding transverse sections through the trunk (J′–L′) and fin (M′–O′) musculature. All genes are expressed in the slow and fast compartments of the myotome and in the pectoral fins. In addition, lama2 is expressed in the posterior hypaxial muscle covering the yolk (M).

Expression of the major muscle laminin genes (lama2, lamb2, and lamc1) in vibratome sections of post-juvenile (15 mm) zebrafish. A: In situ hybridization of the fast myosin heavy chain (MyHC) gene shows expression in the fast but not slow muscle (arrowheads), shown in both transverse (A, A′) and sagittal (A″) sections. In situ hybridization on transverse sections of zebrafish muscle stained for lama2 (B, B′), lamb2 (C, C′), and lamc1 (D, D′) show expression in the fast and slow muscle. Sagittal sections of zebrafish muscle stained for lama2 (B″), lamb2 (C″), and lamc1 (D″) show expression concentrated near the myosepta.

Lama4 expression during zebrafish development. Lama4 is expressed in the myotome during the 16-somite stage (A and transverse section A′). Lateral view of larvae at 24 hpf (B, B″) and corresponding transverse section (B′) shows staining in the fast and slow compartments. At 48 hpf, lama4 is expressed along the horizontal myosepta (C, C″) and in small cells throughout the myotome in transverse section (C′). Whole-mount view of lama4 expression at 72 hpf (D, D″) and transverse section (D′) shows staining along the periphery of the myotome and at the septa. Transverse sections of lama4 expression in the epithelium surrounding the atrium (D, inset). Transverse (E, E′) and sagittal (E″) vibratome sections of zebrafish muscle from post-juvenile (15 mm) fish show lama4 expression in cells scattered throughout the myotome.

Lamb1, lamb4, and lamc3 show specific spatial and temporal expression in the zebrafish myotome by in situ hybridization. A–I: Lateral view, whole mount. A′–I′: Lateral view of trunk musculature. A″–I″: Transverse section through the trunk musculature. At 24 hpf (A, A′, A″), lamb1 expression is seen in the fast and slow muscle, which by 48 hpf (B, B′, B″) and 72 hpf (C, C′, C″) extends to the apices of the myotome. Lamb4 is expressed in the fast and slow muscle at 24 hpf (D, D′, D″) and in the skin at 48 hpf (E, E′, E″) and 72 hpf (F, F′, F″). At 24 hpf (G, G′, G″), lamc3 expression is in two stripes along the trunk musculature and at 48 hpf (H, H′, H″) and 72 hpf (I, I′, I″) is expressed in the gut and neural tube.

Whole mount in situ hybridization for laminin genes not expressed in the muscle during zebrafish development. Lama1 (A–D), lama3 (E–H), lama5 (I–L), lamb1b (M–P), and lamb2l (O–T) are shown for 16-somite, 24-, 48-, and 72-hpf stages.