title: Characterization of recessive RYR1 mutations in core myopathies.
abstract: We have characterized at the molecular level, three families with core myopathies carrying apparent recessive mutations in their RYR1 gene and studied the pharmacological properties of myotubes carrying endogenous mutations as well as the properties of mutant channels expressed in HEK293 cells. The proband of family 1 carried p.Ala1577Thr+p.Gly2060Cys in trans, having inherited a mutation from each parent. Immunoblot analysis of proteins from the patient's skeletal muscle revealed low levels of ryanodine receptor (RyR1) but neither substitution alone or in combination affected the functional properties of RyR1 channels in a discernable way. Two affected siblings in family 2 carried p.Arg109Trp+p.Met485Val substitutions in cis, inherited from the unaffected father. Interestingly, both affected siblings only transcribed the mutated paternal allele in skeletal muscle, whereas the maternal allele was silent. Single-channel measurements showed that recombinant, mutant RyR1 channels carrying both substitutions lost the ability to conduct Ca2+. In this case as well, low levels of RyR1 were present in skeletal muscle extracts. The proband of family 3 carried p.Ser71Tyr+p.Asn2283His substitutions in trans. Recombinant channels with Asn2283His substitution showed an increased activity, whereas recombinant channels with p.Ser71Tyr+p.Asn2283His substitution lost activity upon isolation. Taken together, our data suggest major differences in the ways RYR1 mutations may affect patients with core myopathies, by compromising RyR1 protein expression, stability and/or activity.
authors.affiliation: The Dubowitz Neuromuscular Centre, Imperial College, Hammersmith Hospital, London, UK.
authors.forename: Haiyan
authors.initials: H
authors.lastname: Zhou
authors.forename: Naohiro
authors.initials: N
authors.lastname: Yamaguchi
authors.forename: Le
authors.initials: L
authors.lastname: Xu
authors.forename: Ying
authors.initials: Y
authors.lastname: Wang
authors.forename: Caroline
authors.initials: C
authors.lastname: Sewry
authors.forename: Heinz
authors.initials: H
authors.lastname: Jungbluth
authors.forename: Francesco
authors.initials: F
authors.lastname: Zorzato
authors.forename: Enrico
authors.initials: E
authors.lastname: Bertini
authors.forename: Francesco
authors.initials: F
authors.lastname: Muntoni
authors.forename: Gerhard
authors.initials: G
authors.lastname: Meissner
authors.forename: Susan
authors.initials: S
authors.lastname: Treves
mesh_terms: D019943:Amino Acid Substitution; D001483:Base Sequence; D002118:Calcium / Q000378:metabolism; D002460:Cell Line; D018076:DNA, Complementary / Q000235:genetics; D005260:Female; D005808:Genes, Recessive; D006801:Humans; D066298:In Vitro Techniques; D008297:Male; D008564:Membrane Potentials; D018482:Muscle, Skeletal / Q000378:metabolism / Q000473:pathology; D017570:MyoD Protein / Q000235:genetics / Q000378:metabolism; D020512:Myopathy, Central Core / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D010375:Pedigree; D010641:Phenotype; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D019837:Ryanodine Receptor Calcium Release Channel / Q000235:genetics* / Q000378:metabolism; D014161:Transduction, Genetic
chemical_list: D018076:DNA, Complementary; D017570:MyoD Protein; C057363:MyoD1 myogenic differentiation protein; D011994:Recombinant Proteins; D019837:Ryanodine Receptor Calcium Release Channel; D002118:Calcium