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ABSTRACT: Objective
To identify the genetic cause of isolated inclusion body myopathy (IBM) with autosomal dominant inheritance in 2 families.Methods
Genetic investigations were performed using whole-exome and Sanger sequencing of the heterogeneous nuclear ribonucleoprotein A1 gene (hnRNPA1). The clinical and pathologic features of patients in the 2 families were evaluated with neurologic examinations, muscle imaging, and muscle biopsy.Results
We identified a missense p.D314N mutation in hnRNPA1, which is also known to cause familial amyotrophic lateral sclerosis, in 2 families with IBM. The affected individuals developed muscle weakness in their 40s, which slowly progressed toward a limb-girdle pattern. Further evaluation of the affected individuals revealed no apparent motor neuron dysfunction, cognitive impairment, or bone abnormality. The muscle pathology was compatible with IBM, lacking apparent neurogenic change and inflammation. Multiple immunohistochemical analyses revealed the cytoplasmic aggregation of hnRNPA1 in close association with autophagosomes and myonuclei. Furthermore, the aberrant accumulation was characterized by coaggregation with ubiquitin, sequestome-1/p62, valosin-containing protein/p97, and a variety of RNA-binding proteins (RBPs).Conclusions
The present study expands the clinical phenotype of hnRNPA1-linked multisystem proteinopathy. Mutations in hnRNPA1, and possibly hnRNPA2B1, will be responsible for isolated IBM with a pure muscular phenotype. Although the mechanisms underlying the selective skeletal muscle involvement remain to be elucidated, the immunohistochemical results suggest a broad sequestration of RBPs by the mutated hnRNPA1.
SUBMITTER: Izumi R
PROVIDER: S-EPMC4809462 | biostudies-literature | 2015 Oct
REPOSITORIES: biostudies-literature
Izumi Rumiko R Warita Hitoshi H Niihori Tetsuya T Takahashi Toshiaki T Tateyama Maki M Suzuki Naoki N Nishiyama Ayumi A Shirota Matsuyuki M Funayama Ryo R Nakayama Keiko K Mitsuhashi Satomi S Nishino Ichizo I Aoki Yoko Y Aoki Masashi M
Neurology. Genetics 20150924 3
<h4>Objective</h4>To identify the genetic cause of isolated inclusion body myopathy (IBM) with autosomal dominant inheritance in 2 families.<h4>Methods</h4>Genetic investigations were performed using whole-exome and Sanger sequencing of the heterogeneous nuclear ribonucleoprotein A1 gene (hnRNPA1). The clinical and pathologic features of patients in the 2 families were evaluated with neurologic examinations, muscle imaging, and muscle biopsy.<h4>Results</h4>We identified a missense p.D314N mutat ...[more]