Therapeutic effects of novel type 1 ryanodine receptor inhibitor on malignant hyperthermia

Ca2+-induced Ca2+ release (CICR) is mediated by ryanodine receptors, a Ca2+ release channel in the sarcoplasmic/endoplasmic reticulum (SR/ER), and plays an important role in various tissues. Type 1 ryanodine receptor (RYR1) plays a key role during excitation–contraction coupling of skeletal muscle. Mutations in RYR1 overactivate the channel to cause malignant hyperthermia (MH). MH is a serious complication characterized by skeletal muscle rigidity and elevated body temperature in response to commonly used inhalational anesthetics. Thus far, >300 mutations in the RYR1 gene have been reported in patients with MH. Some heat stroke triggered by exercise or environmental heat stress is also related to MH mutations in the RYR1 gene. The only drug approved for ameliorating the symptoms of MH is dantrolene, which has been first developed in the 1960s as a muscle relaxant. However, dantrolene has several disadvantages for clinical use: poor water solubility, which makes rapid preparation difficult in emergency situations, and long plasma half-life, which causes long-lasting side effects such as muscle weakness. Here, we show that a novel RYR1-selective inhibitor, 6,7-(methylenedioxy)-1-octyl-4-quinolone-3-carboxylic acid (compound 1 [Cpd1]), effectively rescues MH and heat stroke in new mouse model (RYR1-p.R2509C) relevant to MH. Cpd1 has great advantages of higher water solubility and shorter plasma half-life compared with dantrolene. Our data suggest that Cpd1 has the potential to be a promising new candidate for effective treatment of patients carrying RYR1 mutations. Finally, we have recently identified that heat directly activates RYR1, which induces Ca2+ release from intracellular stores. Our results provide direct evidence that heat induces Ca2+ release (HICR) from the SR through the mutants rather than wild type RYR1, causing an immediate rise in the cytosolic Ca2+ concentration.

Therapies for RYR1-Related Myopathies: Where We Stand and the Perspectives

: RyR1-related myopathies are a family of genetic neuromuscular diseases due to mutations in the RYR1 gene. No treatment exists for any of these myopathies today, which could change in the coming years with the growing number of studies dedicated to the pre-clinical assessment of various approaches, from pharmacological to gene therapy strategies, using the numerous models developed up to now. In addition, the first clinical trials for these rare diseases have just been completed or are being launched. We review the most recent results obtained for the treatment of RyR1-related myopathies, and, in view of the progress in therapeutic development for other myopathies, we discuss the possible future therapeutic perspectives for RyR1-related myopathies.

Variant landscape of the RYR1 gene based on whole genome sequencing of the Singaporean population

Background The RYR1 gene codes for a ryanodine receptor which is a calcium release channel in the skeletal muscle sarcoplasmic reticulum. It is associated with Malignant Hyperthermia (MH) and several congenital myopathies including Central Core Disease (CCD), Multiminicore Disease (MMD) and Congenital Fibre-Type Disproportion (CFTD). There is currently little information on the epidemiology of RYR1 variants in Asians. Our study aims to describe the RYR1 variant landscape in a Singapore cohort unselected for RYR1-associated conditions. Methods Data was retrieved from the SG10K pilot project, where whole genome sequencing was performed on volunteers unselected and undetermined for RYR1-associated conditions. Variants were classified based on pathogenicity using databases ClinVar and InterVar. Allele frequencies of pathogenic variants were compared between Chinese, Indians and Malays. Using databases ExAC, GnomAD and GenomeAsia 100k study, we further compared local allele frequencies to those in Europe, America and Asia. Results Majority of the RYR1 variants were missense mutations. We identified four pathogenic and four likely pathogenic RYR1 variants. All were related to the aforementioned RYR1-associated conditions. There were 6 carriers of RYR1 pathogenic variants amongst 4810 individuals, corresponding to an allele frequency of 0.06%. The prevalence of pathogenic variants was the highest amongst Indians (4 in 1127 individuals). Majority of pathogenic and likely pathogenic mutations were missense and located in mutational hotspots. These variants also occurred at higher frequencies in Asians than globally. Conclusion This study describes the variant landscape of the RYR1 gene in Singapore. This knowledge will facilitate local efforts in developing precision medicine.

DNA-type results of Landrace sows for RYR1-gene and its association with productivity

Recently the assessment of QTL genes has been a relevant focus of research. Among other genes, the RYR1 is one of the most important. Research on this gene for Landrace sows of Ukrainian selection has been insufficient. This fact confirms the need for our work. A total of 63 Landrace sows from different families were evaluated by reproductive qualities for two generations. A comprehensive assessment of the sows’ reproductive ability was performed using the SIRQS-index. Determination of polymorphism in the RYR1 gene in pigs was performed by using DNA-typing of animals. Genetic potential was calculated between two generations “mother-daughter”. By assessment of polymorphism of the RYR1 gene, it was found that 6.3% of the Landrace sows were the carriers for the mutant allele of the RYR1 gene. No animals with the RYR1nn genotype were detected. Accordingly, animals with the RYR1NN genotype accounted for 93.6%. The frequency of the N allele of the RYR1 gene was 0.97, the n frequency of the RYR1 gene allele was 0.03. Sows with RYR1NN genotype had a higher level of reproductive ability compared to the RYR1Nn genotype. RYR1NN genotype also had a higher level of genetic potential. The greatest progress was established between generations of Landrace sows which were carriers for the mutant allele. The highest values of this progress were by the NBA, the lowest – by the NW. On the contrary, there was regression between populations for part of the population (Landrace sows of Ukrainian selection of RYR1Nn genotype) by the all estimated indicators of reproductive ability. Sows that were free of the mutant allele of the RYR-1 gene had high SIRQS index. The phenotypic consolidation coefficients by the NBA were lower for sows free of the mutant allele than for its carrier. The advantage of sows free of the mutant allele of the RYR-1 gene over its carrier sows was established in almost all assessed indicators of reproductive ability. No significant differences in the level of consolidation of reproductive ability between sows with different allelic variants of the RYR-1 gene were established. The higher productive level of sows with RYR1NN genotype is reflected in the indicators of economic efficiency of production. It allows higher levels of profitability to be obtained and net profit to be increased by 1093 UAH compared to sows with RYR1Nn genotype. The further monitoring of the studied gene and the gradual elimination of carriers of the mutant allele is a promising direction in breeding work.