Fig. 3.
Accelerated progression of myogenesis in Dll1 mutant embryos. (a–i) Premature and excessive generation of differentiated myotomal myocytes were visualized by whole-mount immunohistochemistry using anti-MHC (a–f) and anti-desmin (g–i) antibodies. Fully differentiated myocytes appear earlier (arrowheads in b and c), and they are more abundant in early myotomes (brackets in d–f, arrowheads in g–i). (j–zs) MRF expression in myotomes (j–y) and limb buds (z–zs) at the indicated stages detected by whole-mount in situ hybridization (j–u and x–zs) in whole embryos (j, k, p–s, x–zc, zf–zm, zp–zs) or vibratome sections (l–o, t, u, zd, ze, zn, zo) or by immunohistochemistry on sections (v and w). MyoD expression in somites of the cervical (j–m) and upper trunk (n and o) region is shown. Black arrowheads point to the regions of low MyoD expression in wild-type embryos. (p and q) Similar initiation of Myogenin expression (black arrowheads) and subsequent increase in myogenin-expressing cells (r–w). (x and y) Accelerated up-regulation of Myf6 (red arrowheads) in cervical myotomes. Accelerated up-regulation of MyoD (z–zi) and Myogenin (zj–zs) in limb buds is shown. Red arrowheads point to expression domains in mutant fore (fl) and hind (hl) limb buds.