Fig. 5. The -58/-56.6 region contains elements that direct transgene expression to distinct regions of the somite, as well as to the limb buds and hypoglossal cord. X-gal staining of embryos at E11.5 (38-40 somites) in which the Myf5-nlacZ transgene contains a -58/-56.6 kb fragment (A) or subfragments of it: -58/-57 (B), -57.5/-56.6 (F) or -57.5/-57 (H). In A, expression is no longer seen in the brain (compare with Fig. 4D), but in somites, limb buds and hypoglossal cord. In B, the -58/-57 subfragment directs expression to the limb buds and hypoglossal cord (black arrow) and to the epaxial and hypaxial extremities of the somite. The cryostat section in C (stained with Eosin), corresponds to a transverse section (white line in B) at the thoracic level of embryo (B). Higher magnifications (D,E) show ß-galactosidase-positive cells in the epithelial structures of the epaxial lip (D) and hypaxial somitic bud (E). In F, somitic expression is mainly seen in the epaxial intercalated region of the myotome, shown on a transverse cryostat section at the thoracic level (white line) in G. The outline of the myotome, which is marked by immune staining with a myosin heavy chain antibody (not shown) is presented as a broken line. In H, the 500 bp (-57.5/-57) fragment directs expression to the limb buds, hypoglossal cord, and epaxial and hypaxial extremities of the somite.

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