Allele frequency of muscular genetic disorders in bull-catching (vaquejada) quarter horses.

Quarter horses (QH), a prominent athletic breed in Brazil, are affected by muscular genetic disorders such as myosin-heavy chain myopathy (MYHM), polysaccharide storage myopathy (PSSM1), hyperkalemic periodic paralysis (HyPP), and malignant hyperthermia (MH). Bull-catching (vaquejada), primarily involving QH, is a significant equestrian sport in Brazil. Since the allele frequencies (AF) of MYHM, PSSM1, HyPP, and MH in vaquejada QH remain unknown, this study evaluated the AF in 129 QH vaquejada athletes, specifically from the Brazilian Northeast. These variants were exclusively observed in heterozygosity. The MYHM exhibited the highest AF (0.04 ±0.01), followed by PSSM1 (0.01 ±0.01) and the HyPP variant (0.004 ±0.01), while the MH variant was not identified in this study. This study represents the first identification of these variants in vaquejada QH, emphasizing the need to implement measures to prevent the transmission of pathogenic alleles and reduce the occurrence of clinical cases of these genetic diseases.

Study of the mutation causing type 1 polysaccharide storage myopathy in a Mangalarga Marchador population used in breeding programs / Estudo da mutação causadora da miopatia por acúmulo de polissacarídeo tipo 1 em uma população de cavalos Mangalarga Marchador utilizados em programas de melhoramento

The Mangalarga Marchador (MM) breed, which originated in Brazil, constitutes the largest number of horses in the country. The animals are versatile and used in several sports because of major investments made for the genetic improve-ment of the breed. In recent decades, advances in molecular techniques enabled the identification of genetic diseases in hor-ses. Conducting molecular tests and determining the occurrence of mutations are fundamental for the early identification and prevention of abnormalities. Among the known genetic diseases that occur in horses, the c.926G>A mutation in the GYS1gene that causes type 1 polysaccharide storage myopathy (PSSM1) stands out, because it has been identified in several breeds of horses. Although myopathy is common in MM horses, the occurrence of the c.926G>A mutation in the GYS1 gene has not yet been evaluated. The lack of knowledge about the possible presence of PSSM1 averts the adoption of control measures to prevent the spread of the disease in MM horses. Therefore, the aim of this study was to verify the occurrence of the muta-tion that causes PSSM1 in MM horses used in breeding programs. Blood DNA was extracted and the region of the GYS1gene containing the mutation was amplified and sequenced. No mutation in the GYS1 gene was found in the evaluated sam-ples. However, since clinical signs of myopathy are frequently observed in MM horses, further studies, including histological analysis, are necessary to establish the underlying causes. In addition, if there is a genetic pattern of occurrence, molecular studies should be considered.(AU)

A raça Mangalarga Marchador (MM), originária do Brasil, constitui a raça de maior número de equinos no país. Os animais são versáteis e utilizados em diversos esportes devido aos seus grandes investimentos em melhoramento genético. Nas últimas décadas, o avanço das técnicas moleculares permitiu a identificação de doenças genéticas em cavalos. A realização de testes moleculares e a determinação da ocorrência de mutações são fundamentais para a identificação precoce e prevenção de anormalidades. Dentre as doenças genéticas conhecidas em equinos, destaca-se a mutação c.926G>A no gene GYS1 causadora da miopatia por acúmulo de polissacarídeo tipo 1 (PSSM1), pois foi identificada em diversas raças equinas. Embora a miopatia seja comum em cavalos MM, a ocorrência da mutação c.926G>A no gene GYS1 ainda não foi avaliada. A falta de conhecimento sobre a possível presença de PSSM1 inviabiliza a adoção de medidas de controle para prevenir a disseminação da doença em equinos MM. Portanto, o objetivo deste estudo foi verificar a ocorrência da mutação causadora de PSSM1 em cavalos MM utilizados em programas de melhoramento. O DNA sanguíneo foi extraído e a região do gene GYS1contendo a mutação foi amplificada e sequenciada. Nenhuma mutação no gene GYS1 foi encontrada nas amostras avaliadas. No entanto, como sinais clínicos de miopatia são frequentemente observados em cavalos com MM, mais estudos, incluindo análises histológicas, são necessários para estabelecer as causas subjacentes. Além disso, se houver um padrão genético de ocorrência, estudos moleculares devem ser considerados.(AU)

Pathological findings of post-anesthetic myopathy associated with type 1 polysaccharide storage myopathy in a percheron horse

Background: Post-anesthetic myopathy is the most common complication associated with general anesthesia in horses. Polysaccharide storage myopathy (PSSM) is characterized by an abnormal accumulation of glycogen and glycogen-related polysaccharides in the skeletal muscle, which is categorized in type 1 (PSSM1) and type 2 (PSSM2). The purpose of this study is to report the clinical, pathological and molecular findings in a Percheron mare with post-anesthetic myopathy associated with a PSSM1. Case: A 9-year-old Percheron mare was submitted to a caesarean section due to clinical dystocia during labor. Xylazine was employed during pre-anesthesia, followed by induction with ketamine and diazepam, while anesthetic maintenance was obtained with isoflurane. The mare showed good recovery, however 24 h later, sternal recumbency and hyperthermia (41° C) were observed. The mare was euthanized, and a necropsy was performed. Samples of multiple tissues were collected and routinely processed for histology. At necropsy, segments of skeletal muscles had bilateral pale areas. The kidneys had old and recent infarcts. The heart had whitish areas in the myocardium. The brain showed focally extensive reddish areas, with flattening of gyri. Histologically, skeletal muscle fibers had in the sarcoplasm multiple homogeneous globular clear eosinophilic formations, in addition to mild hyaline necrosis. In the heart and in the kidney, there were extensive areas of acute coagulative necrosis. The brain showed marked multifocal fibrinoid degeneration of vessels and hemorrhage. Refrigerated liver samples were submitted to DNA extraction to detect mutations in the GYS1 (type 1 PSSM) and RyR1 genes (malignant hyperthermia). A positive result for a homozygous dominant mutation in GYS1 (type 1 PSSM) was observed, while the mutation responsible for malignant hyperthermia was not identified.[...]

Pathological findings of post-anesthetic myopathy associated with type 1 polysaccharide storage myopathy in a percheron horse

Background: Post-anesthetic myopathy is the most common complication associated with general anesthesia in horses. Polysaccharide storage myopathy (PSSM) is characterized by an abnormal accumulation of glycogen and glycogen-related polysaccharides in the skeletal muscle, which is categorized in type 1 (PSSM1) and type 2 (PSSM2). The purpose of this study is to report the clinical, pathological and molecular findings in a Percheron mare with post-anesthetic myopathy associated with a PSSM1. Case: A 9-year-old Percheron mare was submitted to a caesarean section due to clinical dystocia during labor. Xylazine was employed during pre-anesthesia, followed by induction with ketamine and diazepam, while anesthetic maintenance was obtained with isoflurane. The mare showed good recovery, however 24 h later, sternal recumbency and hyperthermia (41° C) were observed. The mare was euthanized, and a necropsy was performed. Samples of multiple tissues were collected and routinely processed for histology. At necropsy, segments of skeletal muscles had bilateral pale areas. The kidneys had old and recent infarcts. The heart had whitish areas in the myocardium. The brain showed focally extensive reddish areas, with flattening of gyri. Histologically, skeletal muscle fibers had in the sarcoplasm multiple homogeneous globular clear eosinophilic formations, in addition to mild hyaline necrosis. In the heart and in the kidney, there were extensive areas of acute coagulative necrosis. The brain showed marked multifocal fibrinoid degeneration of vessels and hemorrhage. Refrigerated liver samples were submitted to DNA extraction to detect mutations in the GYS1 (type 1 PSSM) and RyR1 genes (malignant hyperthermia). A positive result for a homozygous dominant mutation in GYS1 (type 1 PSSM) was observed, while the mutation responsible for malignant hyperthermia was not identified.[...](AU)