Figure 1.

Skeletal muscle formation in mouse embryos. Myotome formation in somites of 11-d.p.c. embryos: Des −/+ (A) and Des −/− (B) embryos were stained for β-galactosidase activity. All myogenic cells appeared blue with a higher intensity in the homozygous (two LacZ copies) than in the heterozygous (one LacZ copy). We observed a normal dermomyotome ventral extension at the thoracic level. h, heart; dm, dermomyotome; hg, hindgut; hl, hindlimb. Muscle growth in 13.5–15-d.p.c embryos in the absence of desmin: Des −/− 13.5-d.p.c. (C) and 15-d.p.c. (D) embryos were stained for β-galactosidase activity. All myofibers are stained blue. We observed a normal morphogenesis and growth of the skeletal muscles. ld, latissimus dorsi; cm, cutaneous maximus; d, deltoidus; t, trapezius. Formation of head and limb musculature at 16 d.p.c. in Des −/− fetuses: β-galactosidase activity in head muscles (E), tongue (F), forelimb (G), and hindlimb musculature (H). bb, biceps brachii; tb, triceps brachii; ad, acromiodeltoidus; sd, spinodeltoidus; e, extensor; f, flexor; vl, vastus lateralis; ta, tibialis anterior; s, soleus.