title: Novel double and single ryanodine receptor 1 variants in two Austrian malignant hyperthermia families.
abstract: BACKGROUND
  Malignant hyperthermia (MH) is a potentially lethal genetic disorder in response to volatile anesthetics and depolarizing muscle relaxants. To support the claim that a novel genetic variant causes MH, it is necessary to demonstrate that it has significant effects on the sensitivity of the ryanodine receptor (RYR1) calcium channel. In this study we focused on 2 Austrian families with strong MH disposition and new RYR1 variants.
  
  
  METHODS
  We sequenced the entire coding region of the RYR1 from 2 Austrian MH individuals. Genotype-phenotype segregation and evolutionary conservation of the variants were considered. On a functional level, Ca(2+) release experiments with fura-2-acetoxymethyl ester were performed in cultured skeletal muscle cells derived from individuals carrying the new variants and compared with control cells from nonsusceptible individuals. Caffeine, 4-chloro-m-cresole (4-CmC), and halothane were used as specific Ca(2+) releasing agents.
  
  
  RESULTS
  The variant p.A612P in family A segregated with an MH-susceptible phenotype and cells showed an increased sensitivity for all Ca(2+)-releasing substances tested. In family B, 2 variants (p.R2458H/p.R3348C) were identified. While p.R2458H and p.R2458H/p.R3348C segregated with an MH-susceptible diagnosis, p.R3348C alone showed an MH equivocal diagnosis. Ca(2+)-release experiments showed that exchanges of these highly conserved amino acids increased the sensitivities for the substances tested (except 4-CmC with p.R2458H and p.R3348C) when compared with the MH-negative control group.
  
  
  CONCLUSIONS
  Our results suggest that these variants are new causative MH variants.
authors.affiliation: Department of Special Anaesthesia and Pain Therapy, Medical University Vienna, Waehringer Guertel 18-20A-1090 Vienna, Austria.
authors.forename: Alexius
authors.initials: A
authors.lastname: Kaufmann
authors.forename: Birgit
authors.initials: B
authors.lastname: Kraft
authors.forename: Andrea
authors.initials: A
authors.lastname: Michalek-Sauberer
authors.forename: Marta
authors.initials: M
authors.lastname: Weindlmayr
authors.forename: Hans G
authors.initials: HG
authors.lastname: Kress
authors.forename: Ferdinand
authors.initials: F
authors.lastname: Steinboeck
authors.forename: Lukas G
authors.initials: LG
authors.lastname: Weigl
mesh_terms: D019943:Amino Acid Substitution / Q000235:genetics; D000768:Anesthesia, General; D018685:Anesthetics, Inhalation / Q000009:adverse effects; D002110:Caffeine / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism; D002478:Cells, Cultured; D000697:Central Nervous System Stimulants / Q000494:pharmacology; D002648:Child; D003593:Cytoplasm / Q000187:drug effects / Q000378:metabolism; D018076:DNA, Complementary / Q000235:genetics; D004305:Dose-Response Relationship, Drug; D014644:Genetic Variation; D006221:Halothane / Q000009:adverse effects; D006801:Humans; D008297:Male; D008305:Malignant Hyperthermia / Q000235:genetics*; D018485:Muscle Fibers, Skeletal / Q000187:drug effects / Q000378:metabolism; D018482:Muscle, Skeletal / Q000473:pathology; D010375:Pedigree; D016133:Polymerase Chain Reaction; D019837:Ryanodine Receptor Calcium Release Channel / Q000235:genetics*; D014068:Tonsillectomy
chemical_list: D018685:Anesthetics, Inhalation; D000697:Central Nervous System Stimulants; D018076:DNA, Complementary; D019837:Ryanodine Receptor Calcium Release Channel; D002110:Caffeine; D002118:Calcium; D006221:Halothane