Journal Article

A novel ryanodine receptor mutation and genotype–phenotype correlation in a large malignant hyperthermia New Zealand Maori pedigree

Rosemary L. Brown, A. Neil Pollock, Kenneth G. Couchman, Michael Hodges, David O. Hutchinson, Rupene Waaka, Patrick Lynch, Tommie V. McCarthy and Kathryn M. Stowell

in Human Molecular Genetics

Volume 9, issue 10, pages 1515-1524
Published in print June 2000 | ISSN: 0964-6906
Published online June 2000 | e-ISSN: 1460-2083 | DOI: http://dx.doi.org/10.1093/hmg/9.10.1515
A novel ryanodine receptor mutation and  genotype–phenotype correlation in a large  malignant hyperthermia New Zealand Maori pedigree

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Malignant hyperthermia (MH) is a pharmacogenetic disorder that predisposes to a sometimes fatal hypermetabolic reaction to halogenated anaesthetics. MH is considered to originate from abnormal regulation of skeletal muscle Ca2+ release. Current diagnosis of MH susceptibility (MHS) relies on in vitro contracture testing (IVCT) of skeletal muscle. The ryanodine receptor (RYR1) encoding the major Ca2+ release channel in the skeletal muscle sarcoplasmic reticulum has been shown to be mutated in a number of MH pedigrees. The large Maori pedigree reported here is the largest MHS pedigree investigated to date and comprises five probands who experienced clinical episodes of MH and 130 members diagnosed by the IVCT. Sequencing of the 15 117 bp RYR1 cDNA in a MHS individual from this pedigree identified a novel C14477T transition that results in a Thr4826 to Ile substitution in the C-terminal region/transmembrane loop of the skeletal muscle ryanodine receptor. This is the first mutation in the RyR1 C-terminal region associated solely with MHS. Although linkage analysis showed strong linkage (max LOD, 11.103 at θ = 0.133) between the mutation and MHS in the pedigree using the standardized European IVCT phenotyping protocol, 22 MHS recombinants were observed. The relationship between the IVCT response and genotype was explored and showed that as IVCT diagnostic cut-off points were made increasingly stringent, the number of MHS discordants decreased with complete concordance between the presence or absence of the C14477T mutation and MHS and MH normal phenotypes, respectively, using a cut-off of 1.2 g tension at 2.0 mM caffeine and 1.8 g tension at 2.0% halothane. Many MHS pedigrees investigated have been excluded from linkage to the RYR1 gene on the basis of a small number of recombinants; however, the linkage analysis reported here suggests that other recombinant families excluded from linkage to the RYR1 gene may actually demonstrate linkage as the number of members tested within the pedigrees increases. The high number of discordants observed using the standardized diagnostic cut-off points is likely to reflect the presence of a second MHS susceptibility locus in the pedigree.

Journal Article.  7395 words.  Illustrated.

Subjects: Genetics and Genomics

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