H36-alpha 7 is a novel integrin alpha chain that is developmentally regulated during skeletal myogenesis [published erratum appears in J Cell Biol 1992 Jul;118(1):213]

Abstract

Abstract. H36 is a 120,000-D membrane glycoprotein that is expressed during the differentiation of skeletal muscle . H36 cDNA clones were isolated from a lambda UniZapXR rat myotube cDNA library and sequenced . The deduced amino acid sequence demonstrates that H36 is a novel integrin alpha chain that shares extensive homology with other alpha integrins that includes : (a) the GFFKR sequence found in all alpha integrins; (b) a single membrane spanning region ; (c) conservation of 18 of 22 cysteines ; and (d) a protease cleavage site found in the non-I region integrin alpha chains . The cytoplasmic domain of H36 is unique and additional regions of nonhomology further indicate H36 is distinct from all other alpha chains . In keeping with current nomenclature we designate this alpha chain 0. Northern blots demonstrate that expression of H36-a7 mRNA is regulated both early in the development of the myogenic lineage and later, during terminal differentiation . Detection of H36-a7 mRNA coincides with conversion of H36-myogenic precursor A A continuum of cell interactions takes place throughout the differentiation of skeletal muscle : distinct cell and molecular interactions underlie the development and function ofeach stage. In the early stages ofmyogenesis cells replicate, migrate, and maintain an autonomy from one another that is typical of most other cells . During this stage the primary interactions of cells are with their molecular environment that includes nutrients, growth factors, and extracellular matrix proteins. This serves to increase cell mass and localize the sites of future development . Subsequently, upon termination of the proliferative stage, the cells interact and fuse to form elongate fibers . At this same stage of development the genes that encode the myofibrillar proteins and ATP-generating enzymes are expressed . The transition between these stages of myogenic development is regulated by the interactions of heterodimeric complexes of helix-loophelix proteins with regulatory sites in the genome (Murre et al., 1989;Davis et al ., 1990 ; for review see Olson, 1990) and by the interactions of cells with growth factors (Lim and Hauschka, 1984;Ewton and Florini, 1990;Massague et al., 1986;Jin et al., 1991) and extracellular matrix proteins (Foster et al., 1987;Ocalan et al., 1988) . The assembly of the

Laminin-111 protein therapy prevents muscle disease in the mdx mouse model for Duchenne muscular dystrophy

“…1 A and B). ␤-Galactosidase expression in ␣ 7 ␤gal ϩ/Ϫ muscle cells increased upon myogenic differentiation, consistent with the expression pattern of ␣ 7 -integrin in myoblasts and myotubes (14). These results confirm that the LacZ reporter gene in ␣ 7 ␤gal ϩ/Ϫ muscle cells faithfully reports the transcriptional activity of the ␣ 7 -integrin promoter.…”

6 4 Integrin and Dystroglycan Cooperate to Stabilize the Myelin Sheath

“…F. β1 integrin is up-regulated in dystroglycan and double mutant mice by Western blot analysis (bars in graph indicate standard error of the mean), in parallel with the α7 subunit. In reducing condition, the α7 121 kD and the 35 kD proteolytic fragment are detected in nerves (Song et al, 1992). α6 integrin is not up-regulated in mutants, and almost absent in β4 mutants.…”

Integrin α5 is required for somite rotation and boundary formation in Xenopus

“…Thus, it is also possible that interactions with other extracellular matrix molecules could provide some redundancy in the development of posterior somites. Laminin accumulates around somites and at somite boundaries (Krotoski and Bronner-Fraser, 1990), and integrin ␣7␤1, which binds laminin, is expressed in the myotomes of both chicken (Kil and Bronner-Fraser, 1996) and mouse (Song et al, 1992(Song et al, , 1993. The expression pattern of integrin ␣7 in Xenopus has not been investigated, however, and thus its potential role in somitogenesis remains unclear.…”