Prevalence of the variant c.1775A>C (p.D592A) responsible for myotonia congenita in Brazilian Quarter Horses

Abstract

Equestrian sport is an important segment of Brazilian horse breeding industry. The Quarter Horse (QH) is one of the main horses used in sporting activities in Brazil. Horse performance may be influenced by muscle diseases. About a third of these diseases are resulting from deleterious genetic variants, such as hyperkalemic periodic paralysis, malignant hyperthermia, polysaccharide storage myopathy 1, and myosin heavy chain myopathy. Clinical signs of muscular discomfort and stiffness common in genetic muscle diseases can be found in other muscle diseases in QH, therefore, the absence of a precise etiological diagnosis prevents the adoption of effective therapeutic measures. Therefore, the genotyping of these variants by molecular biology techniques is fundamental in the clinical routine in order to reduce the impact of these diseases in horses' athletes. The allele frequencies of the main variants have already been evaluated in previous studies by our group and some of these studies served as a basis for the adoption of preventive measures for the occurrence of this disease in the Brazilian QH. Although not yet described in QH, a deleterious variant c.1775A>C (p.D592A) in the CLCN1 gene, responsible for congenital myotonia in horses, may cause serious harm to horses. In this sense, the aim of this study will be to evaluate the presence of the CLCN1_c.1775A>C variant in Brazilian QH. Altogether, 80 DNA samples, purified in previous studies, from QH of different horses' disciplines will be used, in order to verify the allele frequency of this variant in the Brazilian QM.