Fig. 1. Upregulation of integrin 7 where sarcoglycan level is reduced. Immunoblotting of microsomal membrane fractions purified from skeletal muscle from mice lacking sarcoglycan subunits or dystrophin. The antibodies used are specific to the integrin 7 splice forms (Itg7A and Itg7B) representing splice variants that alter the cytoplasmic domains of integrin 7 (Mayer et al., 1997). A Coomassie blue-stained loading control is shown in the lower panel of each blot. (A) Upregulation of integrin 7 in muscle null for -sarcoglycan (dsg^–/–). (B) Upregulation of integrin 7 in muscle null for -sarcoglycan (gsg^–/–) and in dystrophin-null mdx muscle. mdx mice have a secondary reduction of sarcoglycan at the plasma membrane (Ohlendieck and Campbell, 1991). (C) Graphical representation of integrin 7 expression from blots shown in A and B. Upregulation of integrin 7 was seen in all three mutant models but was greatest in muscle lacking -sarcoglycan (dsg^–/–) where sarcoglycan loss is greatest (Hack et al., 2000b).