J Anesth. 2018 Apr;32(2):174-181. doi: 10.1007/s00540-018-2451-6. Epub 2018 Jan 17.

Genetic and functional analysis of the RYR1 mutation p.Thr84Met revealed a susceptibility to malignant hyperthermia.


PURPOSE: The aim of this study was to analyze the genetic and functional role of a novel RYR1 variant c.251 C > T (p.Thr84Met) identified in a patient with muscle weakness demonstrating MH susceptibility.
METHODS: DNA testing of family members was conducted for assessment of pathogenicity of the genetic variant. For functional analysis, Ca2+ measurement using patient-derived myotubes and p.Thr84Met RYR1-transfected human embryonic kidney (HEK)-293 cells was performed to evaluate reactivity to RYR1 activators. The half-maximal effective concentration (EC50) values of two RYR1 activators, caffeine and 4-chloro-m-cresol (4CmC), were calculated from the acquired dose-response curves. The EC50 was compared between two groups: for myotubes, the control group and the patient, and for HEK-293 cells, WT and p.Thr84Met.
RESULTS: Dose-response curves for caffeine and 4CmC were shifted to the left in both myotubes and HEK-293 cells compared to controls. The 50% effective concentration values for caffeine and 4CmC were significantly lower in both myotubes and HEK-293 cells compared to controls (P < 0.001 for all comparisons).
CONCLUSIONS: Our results of functional testing indicated RYR1 hypersensitivity to caffeine and 4CmC. We conclude that the genetic variant was associated with MH susceptibility.


筋力低下と悪性高熱を呈する患者にみつかったRYR1の新規バリアントであるc.251C>T (p.Thr84Met)の遺伝学的、機能的役割を解析した。患者の筋管細胞とc.251C>TバリアントをトランスフェクションしたHEK293細胞を用いカルシウム濃度を測定した。RYR1アクチベーターであるカフェインと4CmCの反応曲線は筋管細胞とトランスフェクションHEK293細胞の両方で左方移動し、いずれのEC50値もコントロールに比較し著明に低下していた。これらの結果から、この患者のRYR1バリアントが悪性高熱に感受性を有するといえる。

PMID:  29344738