Gene/Protein Disease Symptom Drug Enzyme Compound
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 11,717 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We describe a new autosomal recessive myopathy of early onset and very slow progression distinguished by the prominent external ophthalmoplegia in 16 subjects of eight families from a large and highly inbred Arab community. Characteristic clinical features include mild facial and skeletal muscle weakness and atrophy more pronounced proximally in the upper limbs, facial dysmorphism and scoliosis associated with conjugate, non-restrictive ocular motility impairment greatest in the upgaze and without ptosis or aberrant eye movements. Orbital MRI in the patients demonstrated atrophy with fatty replacement of the oculorotatory muscles. The major pathological alteration on skeletal muscle biopsy was a marked type 1 fibre predominance with core-like formations. A genome wide search for regions of homozygosity in the affected members from two informative families identified linkage with chromosome 17p13.1-p12 markers. Maximum two-point logarithm of odds scores were obtained at loci D17S1803 and AFMA070WD1 (Zmax = 3.74 at = 0). Two independent recombination events at D17S1812 and D17S947 further defined a critical region of 12 cM. Several genes map to this interval, including a cluster of sarcomeric myosin heavy chain genes. One of these genes, MYH2, is involved in inclusion body myopathy 3, but no exonic mutations were found by direct sequencing. The molecular basis for this new myopathy remains to be identified.
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PMID:A novel autosomal recessive myopathy with external ophthalmoplegia linked to chromosome 17p13.1-p12. 1554 56

Mutations in the RYR1 gene are the most common cause of human congenital myopathies, and patients with recessive mutations are severely affected and often display ptosis and/or ophthalmoplegia. In order to gain insight into the mechanism leading to extraocular muscle (EOM) involvement, we investigated the biochemical, structural and physiological properties of eye muscles from mouse models we created knocked-in for Ryr1 mutations. Ex vivo force production in EOMs from compound heterozygous RyR1p.Q1970fsX16+p.A4329D mutant mice was significantly reduced compared with that observed in wild-type, single heterozygous mutant carriers or homozygous RyR1p.A4329D mice. The decrease in muscle force was also accompanied by approximately a 40% reduction in RyR1 protein content, a decrease in electrically evoked calcium transients, disorganization of the muscle ultrastructure and a decrease in the number of calcium release units. Unexpectedly, the superfast and ocular-muscle-specific myosin heavy chain-EO isoform was almost undetectable in RyR1p.Q1970fsX16+p.A4329D mutant mice. The results of this study show for the first time that the EOM phenotype caused by the RyR1p.Q1970fsX16+p.A4329D compound heterozygous Ryr1 mutations is complex and due to a combination of modifications including a direct effect on the macromolecular complex involved in calcium release and indirect effects on the expression of myosin heavy chain isoforms.
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PMID:Molecular basis of impaired extraocular muscle function in a mouse model of congenital myopathy due to compound heterozygous Ryr1 mutations. 3224 14