Screening of the ryanodine receptor gene in 105 malignant hyperthermia families: novel mutations and concordance with the in vitro contracture test

Abstract

Malignant hyperthermia (MH) in man is an autosomal dominant disorder of skeletal muscle Ca(2+)-regulation. During anesthesia in predisposed individuals, it is triggered by volatile anesthetics and depolarizing muscle relaxants. In >50% of the families, MH susceptibility is linked to the gene encoding the skeletal muscle ryanodine receptor (RYR1), the calcium release channel of the sarcoplasmic reticulum, on chromosome 19q12-13.2. To date, 21 RYR1 mutations have been identified in a number of pedigrees. Four of them are also associated with central core disease (CCD), a congenital myopathy. Screening for these 21 mutations in 105 MH families including 10 CCD families phenotyped by the in vitro contracture test (IVCT) according to the European protocol revealed the following approximate distribution: 9% Arg-614-Cys, 1% Arg-614-Leu, 1% Arg-2163-Cys, 1% Val-2168-Met, 3% Thr-2206-Met and 7% Gly-2434-Arg. In one CCD family, the disease was caused by a recently reported MH mutation, Arg-2454-His. Two novel mutations, Thr-2206-Arg and Arg-2454-Cys were detected, each in a single pedigree. In the 109 individuals of the 25 families with RYR1 mutations cosegregation between genetic result and IVCT was almost perfect, only three genotypes were discordant with the IVCT phenotypes, suggesting a true sensitivity of 98.5% and a specificity of minimally 81.8% for this test. Screening of the transmembraneous region of RYR1 did not yield a new mutation confirming the cytosolic portion of the protein to be of main functional importance for disease pathogenesis.

Multi-Minicore Disease with Susceptibility to Malignant Hyperthermia in Pregnancy

“…The ryanodine receptor gene encodes the key channel that mediates calcium release in skeletal muscle. To date, more than 20 missense mutations in the 15,117-bp coding region of the gene have been found to segregate with the MH-susceptibility trait [10]. Mutation analysis of this gene would provide more accurate information on the inheritance mode.…”

RYR1 mutations in UK central core disease patients: more than just the C-terminal transmembrane region of the RYR1 gene

“…Thr2206Met, 33 Arg2454Cys, 34 Arg2454His, 35 Thr4637Ala, 36 Tyr4796Cys, 6 Ile4898Thr, 37 and 15 mutations: Cys35Arg, Arg163Cys, Gly248Arg, Gly341Arg, Ile403Met, Tyr522Ser, Arg552Trp, Arg614Cys, Arg614Leu, Arg2163Cys, Arg2163His, Gly2434Arg, Arg2435His, Arg2458Cys, and Arg2458His. 15 Further screening was undertaken by fluorescent SSCP (F-SSCP) analysis (exons 6, 11, 17, 39-46) and cycle sequencing using an ABI 377 (exons 91, 95-106).…”

Frequency and localization of mutations in the 106 exons of theRYR1 gene in 50 individuals with malignant hyperthermia

“…Mutations in MHS individuals are detected in three regions (exons 2-17, exons 39-46 and exons 90-104) of the RYR1 gene. However, since the large size of the RYR1 gene (106 exons) makes genetic analysis very laborious and expensive, mutation screening is preferentially performed only in those exons where known mutations are clustered [Barone et al, 1999;Brandt et al, 1999;Lynch et al, 1999;Galli et al, 2002;Robinson et al, 2003;Tilgen et al, 2003;Tammaro et al, 2003;Sambuughin et al, 2001]. This approach has resulted in the identification of mutations in the RYR1 gene in approximately 30-50% of the probands identified as MHS at the in vitro contraction test (IVCT) [European Malignant hyperpyrexia Group, 1984;Robinson et al, 2003], while analysis of the entire RYR1 coding sequence is only rarely performed [Sambuughin et al, 2005;Monnier et al, 2005].…”