35P Generation of a zebrafish knock-in model of exertional heat stroke.

Heat illness is the primary cause of morbidity and mortality among young athletes and people engaged in outdoor activities in hot environments, including military and industrial applications. Heat illness presents on a spectrum from relatively mild heat exhaustion to the most severe, exertional heat stroke (EHS). EHS is a life-threatening emergency that requires rapid cooling and immediate medical assistance, leading to severe organ damage and sometimes death. EHS is a complicated disease resulting from interactions of several contributing factors, including aberrant calcium dynamics in skeletal muscle. This assertion is based on the fact that human and mouse models with abnormalities in skeletal muscle excitation-contraction (EC) coupling have been associated with the onset of heat stroke. However, a complete understanding of the pathogenesis of EHS remains elusive. To further investigate the pathomechanisms in EHS related to the EC-coupling abnormality, we generated zebrafish models with knocking-in an R615C mutation in the zebrafish ryr1b gene using CRISPR/Cas9 system. Zebrafish with homozygous and heterozygous mutations showed normal development and no motor abnormalities under standard husbandry conditions. When exposed to elevated temperatures, severe muscle damage was observed, which was the same manifestation as our previously reported zebrafish model of EHI and malignant hyperthermia (junctin fish). In addition, we observed that caffeine stimulation enhanced muscle dysfunction, providing a more sensitive assessment of disease severity. The platform we have developed will be useful for drug screening and for evaluating new causative genes that may be discovered in the future. [ABSTRACT FROM AUTHOR]