Malignant hyperthermia (MH) is a pharmacogenetic disorder of skeletal muscle which results from anaesthetic-induced disruption to calcium homeostasis. Mutations in the RYR1 and CACN1AS genes encoding the ryanodine (RyR1) and dihydropyridine receptors (DHPR) Ca2+ release channels represent the causative agent in up to 70% of MH susceptible (MHS) populations. The RYR1 screening project has, however, confirmed that up to 30% of MHS patients carry neither RYR1 nor CACN1AS variants and it has been suggested that some modifier genes may exist. Therefore, the aim of the present study is to investigate the relationships between MH susceptibility and genes encoding skeletal muscle Ca2+ channels or accessory proteins. FKBP1A, CASQ1 and JSRP1 genes encoding FKBP12, Calsquestrin1 and JP45 respectively, were selected as candidates for DNA sequencing to screen for potential MH causative mutations. The exonic sequences of DNA samples from MHS patients in whom RYR1 and CACN1AS variants have been excluded were sequenced. DNA sequencing of JSRP1 revealed two variants in the coding region of JP45: p.P108L and p.G150A. The variant p.G150A demonstrated statistically significant increased frequency in MHS individuals compared to MH normal (MHN) populations (p <0.05). Therefore, we hypothesize that p.G150A is associated with MH phenotype. To test this hypothesis, we performed the transmission disequilibrium test which indicated a significant association between the variant p.G150A and MH susceptibility (p <0.05). Western blotting indicated a significant increase in the expression of JP45 in RYR1-HEK293 cells transfected with mutant JSRP1 compared to cells transfected with wild type protein (p <0.05). Furthermore, calcium release measurements demonstrated significant increase in calcium release levels in the RYR1-HEK293 cells expressing mutant JP45 compared with cells expressing wild type JP45 at 1 and 2 mM caffeine concentrations (p < 0.05 and p < 0.01 respectively). In conclusion, JP-45 functions as a modifier protein in the UK MH population.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:582743 |
| Date | January 2012 |
| Creators | Althobiti, Mohammed Abdullatif |
| Publisher | University of Leeds |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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