RESUMO
BACKGROUND: Malignant hyperthermia (MH) is an inherited pharmacogenetic disorder of skeletal muscle, characterised by an elevated calcium release from the skeletal muscle sarcoplasmic reticulum. The dihydropyridine receptor (DHPR) plays an essential role in excitation-contraction coupling and calcium homeostasis in skeletal muscle. This study focuses on the gene CACNA1S which encodes the alpha1 subunit of the DHPR, in order to establish whether CACNA1S plays a major role in MH susceptibility in the UK. METHODS: We investigate the CACNA1S locus in detail in 50 independent MH patients, the largest study to date, to identify novel variants that may predispose to disease and also to characterise the haplotype structure across CACNA1S. RESULTS: We present CACNA1S cDNA sequencing data from 50 MH patients in whom RYR1 mutations have been excluded, and subsequent mutation screening analysis. Furthermore we present haplotype analysis of unphased CACNA1S SNPs to (1) assess CACNA1S haplotype frequency differences between susceptible MH cases and a European control group and (2) analyse population-based association via clustering of CACNA1S haplotypes based on disease risk. CONCLUSION: The study identified a single potentially pathogenic change in CACNA1S (p.Arg174Trp), and highlights that the haplotype structure across CACNA1S is diverse, with a high degree of variability.
Assuntos
Canais de Cálcio/genética , Predisposição Genética para Doença , Hipertermia Maligna/genética , Adolescente , Adulto , Idoso , Sequência de Aminoácidos , Cafeína/farmacologia , Canais de Cálcio Tipo L , Criança , Estudos de Coortes , Feminino , Halotano/farmacologia , Haplótipos , Humanos , Técnicas In Vitro , Masculino , Hipertermia Maligna/fisiopatologia , Pessoa de Meia-Idade , Contração Muscular/efeitos dos fármacos , Contração Muscular/genética , Músculo Esquelético/fisiopatologia , Mutação , Polimorfismo de Nucleotídeo Único , Adulto JovemRESUMO
In this study we present 3 families with malignant hyperthermia (MH), all of Indian subcontinent descent. One individual from each of these families was fully sequenced for RYR1 and presented with the non-synonymous change c.11315G>A/p.R3772Q. When present in the homozygous state c.11315*A is associated with myopathic symptoms.
Assuntos
Hipertermia Maligna/genética , Doenças Musculares/genética , Canal de Liberação de Cálcio do Receptor de Rianodina/genética , Adolescente , Adulto , Idoso , Povo Asiático , Consanguinidade , DNA/genética , DNA Complementar/biossíntese , DNA Complementar/genética , Família , Feminino , Genes Dominantes , Genes Recessivos , Humanos , Imuno-Histoquímica , Masculino , Pessoa de Meia-Idade , Músculo Esquelético/patologia , Doenças Musculares/congênito , Linhagem , Fenótipo , Espasmo/genética , Espasmo/patologiaRESUMO
Hypokalemic periodic paralysis (HypoPP) and malignant hyperthermia (MH) are autosomal-dominant genetically heterogeneous ion channelopathies. MH has been described in patients with HypoPP, suggesting a potential link between these disorders. However, a common genetic determinant has not been described. With the aim of corroborating this association, four candidate genes were screened in two independent HypoPP patients, one of whom was also diagnosed as MH-susceptible and the other as MH-normal by the in vitro contracture test (IVCT). An A>G change at nucleotide 7025 was detected in the RYR1 gene in the HypoPP/MH-susceptible patient. Detection of the same mutation in three independent MH families suggested that 7025A>G represents a novel MH-susceptibility allele and that MH and HypoPP occurred independently in the case presented. Conclusive evidence in support of the hypothesis that MH and HypoPP are allelic was therefore not obtained.
Assuntos
Paralisia Periódica Hipopotassêmica/genética , Hipertermia Maligna/genética , Canais de Potássio de Abertura Dependente da Tensão da Membrana , Adolescente , Adulto , Canais de Cálcio/genética , Canais de Cálcio Tipo L , Análise Mutacional de DNA , Humanos , Masculino , Canal de Sódio Disparado por Voltagem NAV1.4 , Mutação Puntual , Canais de Potássio/genética , Canal de Liberação de Cálcio do Receptor de Rianodina/genética , Canais de Sódio/genéticaRESUMO
Malignant hyperthermia (MH) and central core disease (CCD) are autosomal dominant disorders of skeletal muscle. Susceptibility to MH is only apparent after exposure to volatile anesthetics and/or depolarizing muscle relaxants. CCD patients present with diffuse muscular weakness but are also at risk of MH. Mutations in RYR1 (19q13.1), encoding a skeletal muscle calcium release channel (ryanodine receptor), account for the majority of MH and CCD cases. Fifteen RYR1 N-terminal mutations are considered causative of MH susceptibility, five of which are also associated with CCD. In the first extensive UK population survey, eight of 15 mutations were detected in 85 out of 297 (29%) unrelated MH susceptible cases, with G2434R detected in 53 cases (18%). Mutation type was shown to affect significantly MH phenotypes (in vitro contracture test (IVCT) response to caffeine, halothane, and ryanodine). RYR1 mutations associated with both CCD and MH (R163C, R2163H, R2435H) had more severe caffeine and halothane response phenotypes than those associated with MH alone. Mutations near the amino terminal (R163C, G341R) had a relatively greater effect on responses to caffeine than halothane, with a significantly increased caffeine:halothane tension ratio compared to G2434R of the central domain. All phenotypes were more severe in males than females, and were also affected by muscle specimen size and viability. Discordance between RYR1 genotype and IVCT phenotype was observed in seven families (nine individuals), with five false-positives and four false-negatives. This represents the most extensive study of MH patient clinical and genetic data to date and demonstrates that RYR1 mutations involved in CCD are those associated with one end of the spectrum of MH IVCT phenotypes.
