Disruption of muscle membrane and phenotype divergence in two novel mouse models of dysferlin deficiency

Abstract

Limb girdle muscular dystrophy type 2B and Miyoshi myopathy are clinically distinct forms of muscular dystrophy that arise from defects in the dysferlin gene. Here, we report two novel lines of dysferlin-deficient mice obtained by (a) gene targeting and (b) identification of an inbred strain, A/J, bearing a retrotransposon insertion in the dysferlin gene. The mutations in these mice were located at the 3' and 5' ends of the dysferlin gene. Both lines of mice lacked dysferlin and developed a progressive muscular dystrophy with histopathological and ultrastructural features that closely resemble the human disease. Vital staining with Evans blue dye revealed loss of sarcolemmal integrity in both lines of mice, similar to that seen in mdx and caveolin-3 deficient mice. However, in contrast to the latter group of animals, the dysferlin-deficient mice have an intact dystrophin glycoprotein complex and normal levels of caveolin-3. Our findings indicate that muscle membrane disruption and myofiber degeneration in dysferlinopathy were directly mediated by the loss of dysferlin via a new pathogenic mechanism in muscular dystrophies. We also show that the mutation in the A/J mice arose between the late 1970s and the early 1980s, and had become fixed in the production breeding stocks. Therefore, all studies involving the A/J mice or mice derived from A/J, including recombinant inbred, recombinant congenic and chromosome substitution strains, should take into account the dysferlin defect in these strains. These new dysferlin-deficient mice should be useful for elucidating the pathogenic pathway in dysferlinopathy and for developing therapeutic strategies.

Social approach and repetitive behavior in eleven inbred mouse strains

“…For example, motor deficiencies due to a mutation in dysferlin, observed in A/ J mice [17], may be the underlying cause of apparent low social approach in this strain [30,31]. Olfactory information is a key element of social interaction in mice [13,24,25,36].…”

Genetic Manipulation of Dysferlin Expression in Skeletal Muscle

“…A/J mice, a strain with a homozygous retrotransposon insertion in the Dysf gene described previously, 12 were purchased from Jackson Laboratories (Bar Harbor, ME). To generate dysferlin transgenic mice (Dysf-TG) we fused human dysferlin cDNA (88% identical to mouse) to the human ␣-skeletal actin promoter with an upstream troponin I slow fiber-type enhancer (generously provided by Edna C. Hardeman, University of Sydney).…”

“…Genotyping for the Dysf mutant allele was performed exactly as described previously. 12 All animal experiments were approved by the Institutional Animal Care and Use Committee.…”

“…9,10 To directly test this hypothesis we crossed the skeletal muscle-specific Dysf-TG mouse (C57Bl/6 background) with A/J mice, a mouse strain that develops MD due to a mutation in the Dysf gene, which results in the absence of expression of the dysferlin protein. 12 To assess skeletal muscle disease in these mice, we quantified a number of common dystrophic parameters, such as central nucleation, fibrosis, distribution of myofiber cross-sectional areas, macrophage infiltration, functional recovery from injury, and total serum CK levels (Figure 2). At 8 months of age, histological analysis from H&E-stained sections showed abundant pathology in the quadriceps of Dysf Ϫ/Ϫ mice, moderate pathology in the TA, and low but detectable pathology in the soleus (Figure 2 shown).…”

Therapeutic Possibilities in the Autosomal Recessive Limb-Girdle Muscular Dystrophies

“…1,[35][36][37] The large size of the dysferlin gene makes the application of gene replacement strategies relatively problematic, unless shortened forms of the protein can be shown to be at least partially functional, as has been demonstrated for dystrophin (Krahn et al, personal communication).…”