Type IV collagen is essential for proper function of integrin-mediated adhesion in Drosophila muscle fibers

Abstract

Congenital muscular dystrophy (CMD),

Novel Phenotypic Elements of Type IV Collagenopathy Revealed by the Drosophila Model

“…Similarly, in the isoallelic p.G552D1 and p.G552D2 mutants, the survival rates upon heat selection differed slightly. The line with the p.G552D1 lesion presented survival rates of 26.9% for pupae and 5.3% for adults, whereas the survival rates for the p.G552D2 line were 5.7% and 0.50%, respectively [24,29].…”

“…The second isoallelic pair DTS-L4 and DTS-L5 carried the p.G1205E1 and p.G1205E2 substitutions, respectively, and the DTS-L10 carried the p.G1043S substitution, whereas the b-17 carried the p.G1393E substitution. Importantly, the lesions covered the collagenous domain of the COL4A1 protein [29].…”

“…The basement membrane covering the myofibers appeared distorted, thinned or absent, demonstrating that the mutant COL4A1 protein induced severe oviductal myopathy [24,26]. Integrin deposition in muscle fibers was recorded by punctate staining at the level of Z-discs, overlapping with the signals provided by the Z-disc protein kettin and bordering each sarcomeric unit in immunohistochemical preparation [29]. High expressivity of the trait occurred at low penetrance, i.e., shifting Z-disc integrin-binding sites toward the middle of sarcomeres in col4a1 G552D1 mutants at the restrictive condition ( Figure 1).…”

“…The genome of the fruit fly consists of a pair of type IV collagen genes, col4a1 and col4a2 in a head-to-head orientation, similar to mammals [24]. The mutant phenotype is systemic, affecting the gut [25,26], the excretory organ Malpighian tubules [27,28] and the muscles manifested in muscular dystrophy [29]. The recessive phenotype of the col4a1 -/homozygotes leads to lethality in the late embryonic to early larval phases at the permissive temperature [24].…”

“…In col4a1 fly mutants, we recorded severe myopathy, reduced concentration of COL4A1 protein [24], chronic inflammation, intestinal dysfunction [25], detachment of the cells from the BM by electron microscopy [26], compromised excretory system [27], heavy membrane peroxidation in epithelial cells of the Malpighian tubules [28] and the onset of muscular dystrophy in all mutants [29]. Temperature-sensitive col4a1 alleles in Drosophila were generated by ethyl-methanesulfonate mutagenesis, resulting in G to A transitions in all alleles, in turn leading to glycine substitutions by Glu, Asp and Ser [29]. The phenotypic changes appeared in adult flies following 14 days of incubation at 29 • C and were not reversible, the flies did not recover at 20 • C following a shift in heat.…”