Contribution of Dysferlin Deficiency to Skeletal Muscle Pathology in Asymptomatic and Severe Dystroglycanopathy Models: Generation of a New Model for Fukuyama Congenital Muscular Dystrophy

Abstract

Defects in dystroglycan glycosylation are associated with a group of muscular dystrophies, termed dystroglycanopathies, that include Fukuyama congenital muscular dystrophy (FCMD). It is widely believed that abnormal glycosylation of dystroglycan leads to disease-causing membrane fragility. We previously generated knock-in mice carrying a founder retrotransposal insertion in fukutin, the gene responsible for FCMD, but these mice did not develop muscular dystrophy, which hindered exploring therapeutic strategies. We hypothesized that dysferlin functions may contribute to muscle cell viability in the knock-in mice; however, pathological interactions between glycosylation abnormalities and dysferlin defects remain unexplored. To investigate contributions of dysferlin deficiency to the pathology of dystroglycanopathy, we have crossed dysferlin-deficient dysferlin sjl/sjl mice to the fukutin-knock-in fukutin Hp/− and Large-deficient Large myd/myd mice, which are phenotypically distinct models of dystroglycanopathy. The fukutin Hp/− mice do not show a dystrophic phenotype; however, (dysferlin sjl/sjl: fukutin Hp/−) mice showed a deteriorated phenotype compared with (dysferlin sjl/sjl: fukutin Hp/+) mice. These data indicate that the absence of functional dysferlin in the asymptomatic fukutin Hp/− mice triggers disease manifestation and aggravates the dystrophic phenotype. A series of pathological analyses using double mutant mice for Large and dysferlin indicate that the protective effects of dysferlin appear diminished when the dystrophic pathology is severe and also may depend on the amount of dysferlin proteins. Together, our results show that dysferlin exerts protective effects on the fukutin Hp/− FCMD mouse model, and the (dysferlin sjl/sjl: fukutin Hp/−) mice will be useful as a novel model for a recently proposed antisense oligonucleotide therapy for FCMD.

Abnormal Skeletal Muscle Regeneration plus Mild Alterations in Mature Fiber Type Specification in Fktn-Deficient Dystroglycanopathy Muscular Dystrophy Mice

“…Sarcolemmal attachment to the extracellular matrix through specific glycan structures on αDG is critical for muscle protection against contraction-induced damage [ 14 ]. Accordingly, loss of Fktn or other genes involved in processing the O -Mannose glycan on αDG renders the sarcolemma vulnerable to contraction-induced damage and myonecrosis [ 15 , 16 , 26 , 29 , 30 ]. To determine postnatal disease onset, we evaluated muscle regeneration in Myf5/ Fktn KO muscle by the percentage of eMHC-expressing and centrally nucleated (CN) fibers in the iliopsoas and TA (with EDL) at 2, 4, and 8 weeks old (wko).…”

Report: Fourth International Workshop for Glycosylation Defects in Muscular Dystrophies

“…The possibility of moving to clinical trials with this treatment is currently being addressed. Dr. Motoi Kanagawa presented a new FCMD mouse model, a fukutin-KI/dysferlin-deficient mouse, which can be used for testing the effectiveness of the AON treatment in vivo [13]. He also presented results of AAV gene therapy in fukutin conditional KO mice that more closely resembles that of FCMD patients.…”