Carlos A Ibarra Moreno1, Natalia Kraeva1, Elena Zvaritch1, Lourdes Figueroa2, Eduardo Rios2, Leslie Biesecker3, Filip Van Petegem4, Philip M Hopkins5, Sheila Riazi6. 1. Malignant Hyperthermia Investigation Unit, Department of Anesthesia, University Health Network, University of Toronto, Toronto, ON, Canada. 2. Department of Physiology and Biophysics, Rush University Medical Center, Chicago, IL, USA. 3. Medical Genomics and Metabolic Genetics Branch, National Human Genome Research Institute, Bethesda, MD, USA. 4. Department of Biochemistry and Molecular Biology, The University of British Columbia, Vancouver, BC, Canada. 5. Leeds Institute of Medical Research at St James's, University of Leeds, Leeds, UK; Department of Anaesthesia, St James's University Hospital, Leeds Teaching Hospitals NHS Trust, Leeds, UK. 6. Malignant Hyperthermia Investigation Unit, Department of Anesthesia, University Health Network, University of Toronto, Toronto, ON, Canada. Electronic address: Sheila.Riazi@uhn.ca.
Abstract
BACKGROUND: Malignant hyperthermia (MH) susceptibility is an inherited condition, diagnosed either by the presence of a pathogenic genetic variant or by in vitro caffeine-halothane contracture testing. Through a multi-dimensional approach, we describe the implications of discordance between genetic and in vitro test results in a patient with a family history of possible MH. METHODS: The patient, whose brother had a possible MH reaction, underwent the caffeine-halothane contracture test (CHCT) according to the North American MH Group protocol. Screening of the complete RYR1 and CACNA1S transcripts was done using Sanger sequencing. Additional functional analyses included skinned myofibre calcium-induced calcium release sensitivity, calcium signalling assays in cultured myotubes, and in silico evaluation of the effect of any genetic variants on their chemical environment. RESULTS: The patient's CHCT result was negative but she carried an RYR1 variant c.1209C>G, p.Ile403Met, that is listed as pathogenic by the European Malignant Hyperthermia Group. Functional tests indicated a gain-of-function effect with a weak impact, and the variant was predicted to affect the folding stability of the 3D structure of the RyR1 protein. Based on American College of Medical Genetics and Genomics/Association of Molecular Pathology guidelines, this variant would be characterised as a variant of uncertain significance. CONCLUSIONS: Available data do not confirm or exclude an increased risk of MH for this patient. Further research is needed to correlate RyR1 functional assays, including the current gold standard testing for MH susceptibility, with clinical phenotypes. The pathogenicity of genetic variants associated with MH susceptibility should be re-evaluated.
BACKGROUND:Malignant hyperthermia (MH) susceptibility is an inherited condition, diagnosed either by the presence of a pathogenic genetic variant or by in vitro caffeine-halothanecontracture testing. Through a multi-dimensional approach, we describe the implications of discordance between genetic and in vitro test results in a patient with a family history of possible MH. METHODS: The patient, whose brother had a possible MH reaction, underwent the caffeine-halothanecontracture test (CHCT) according to the North American MH Group protocol. Screening of the complete RYR1 and CACNA1S transcripts was done using Sanger sequencing. Additional functional analyses included skinned myofibre calcium-induced calcium release sensitivity, calcium signalling assays in cultured myotubes, and in silico evaluation of the effect of any genetic variants on their chemical environment. RESULTS: The patient's CHCT result was negative but she carried an RYR1 variant c.1209C>G, p.Ile403Met, that is listed as pathogenic by the European Malignant Hyperthermia Group. Functional tests indicated a gain-of-function effect with a weak impact, and the variant was predicted to affect the folding stability of the 3D structure of the RyR1 protein. Based on American College of Medical Genetics and Genomics/Association of Molecular Pathology guidelines, this variant would be characterised as a variant of uncertain significance. CONCLUSIONS: Available data do not confirm or exclude an increased risk of MH for this patient. Further research is needed to correlate RyR1 functional assays, including the current gold standard testing for MH susceptibility, with clinical phenotypes. The pathogenicity of genetic variants associated with MH susceptibility should be re-evaluated.
Authors: Eric F Pettersen; Thomas D Goddard; Conrad C Huang; Gregory S Couch; Daniel M Greenblatt; Elaine C Meng; Thomas E Ferrin Journal: J Comput Chem Date: 2004-10 Impact factor: 3.376
Authors: P M Hopkins; H Rüffert; M M Snoeck; T Girard; K P E Glahn; F R Ellis; C R Müller; A Urwyler Journal: Br J Anaesth Date: 2015-07-18 Impact factor: 9.166