Antisense oligonucleotide induced pseudoexon skipping and restoration of functional protein for Fukuyama muscular dystrophy caused by a deep-intronic variant

Fukuyama congenital muscular dystrophy (FCMD) is an autosomal recessive disorder caused by fukutin (FKTN) gene mutations. FCMD is the second most common form of childhood muscular dystrophy in Japan, and the most patients possess a homozygous retrotransposal SINE-VNTR-Alu insertion in the 3′-untranslated region of FKTN. A deep-intronic variant (DIV) was previously identified as the second most prevalent loss-of-function mutation in Japanese patients with FCMD. The DIV creates a new splicing donor site in intron 5 that causes aberrant splicing and the formation of a 64-base pair pseudoexon in the mature mRNA, resulting in a truncated nonfunctional protein. Patients with FCMD carrying the DIV present a more severe symptoms, and currently, there is no radical therapy available for this disorder. In the present study, we describe in vitro evaluation of antisense oligonucleotide mediated skipping of pseudoexon inclusion and restoration of functional FKTN protein. A total of 16 19-26-mer antisense oligonucleotide sequences were designed with a 2’-O-methyl backbone and were screened in patient-derived fibroblasts, lymphoblast cells, and minigene splice assays. One antisense oligonucleotide targeting the exonic splice enhancer region significantly induced pseudoexon skipping and increased the expression of normal mRNA. It also rescued FKTN protein production in lymphoblast cells and restored functional O-mannosyl glycosylation of alpha-dystroglycan in patient-derived myotubes. Based on our results, ASO-based splicing correction should be investigated further as a potential treatment for patients with FCMD carrying the DIV.

Acute rhabdomyolysis following viral infection with coxsackie A4 in a 50-day-old infant with Fukuyama congenital muscular dystrophy

BACKGROUND

Fukuyama congenital muscular dystrophy (FCMD), which is characterized by generalized muscle weakness, hypotonia, and motor delay during early infancy, gradually progresses with advanced age. Although acute rhabdomyolysis following infection in patients with FCMD has occasionally been reported, no studies have investigated rhabdomyolysis following viral infection in FCMD patients during early infancy.

CASE REPORT

We report the case of a 50-day-old girl with no apparent symptoms of muscular dystrophy who developed severe acute rhabdomyolysis caused by viral infection, resulting in quadriplegia and respiratory failure therefore requiring mechanical ventilation. Brain magnetic resonance imaging incidentally showed the typical characteristics of FCMD, and FCMD was confirmed by genetic analysis, which revealed a 3-kb retrotransposon insertion in one allele of the fukutin gene and a deep intronic splicing variant in intron 5 in another allele. The virus etiology was confirmed to be Coxsackie A4.

CONCLUSION

We report a severe case of acute rhabdomyolysis with the earliest onset of symptoms due to the Coxsackie A4 virus in a patient with FCMD. The present findings indicate that physicians should consider FCMD with viral infection a differential diagnosis if the patient presents with acute rhabdomyolysis following a fever.