Tg(ACTA1-MYOT*T57I)71Mah

The point mutation responsible for limb-girdle muscular dystrophy type 1A (LGMD1A) in a North American family - substitution of threonine for isoleucine at amino acid position 57 (T57I) of the protein - was introduced into the human myotilin cDNA. This mutant cDNA, comprising 1530 bp of coding sequence, 281 bp of 5' UTR and 485 bp of 3' UTR, with sequence encoding a MYC epitope tag inserted at the beginning of the coding region, was cloned into the HAS-VP1 expression vector downstream of nucleotides -2139 through +239 of the human actin, skeletal, alpha 1 gene followed by the splice acceptor from the SV40 P1 intron; two copies of the SV40 polyadenylation signal follow the 3'UTR of the cDNA. RT-PCR analysis of several tissues detected transgene-derived mRNA only in skeletal muscle, and immunoblot analysis with antibody against MYC demonstrated appropriate expression of the transgene product in multiple striated muscles. Immunohistologic examination of muscle sections revealed uniformity of expression in fibers within a muscle group and similarity of expression in slow, type I and in fast, type II fibers. Expression of the mutant human myotilin is 2.6-fold that of the endogenous mouse protein. (J:110377)