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Background: Canine degenerative myelopathy represents a progressive neurodegenerative disorder impacting the spinal cord. Initial clinical signs of canine degenerative myelopathy are typically observed in animals around 8 years of age. The clinical signs are characterized by general proprioceptive ataxia and spastic paresis of the pelvic limbs, with an irrepressible progression to flaccid paraplegia after 1 year of the appearance of the signs. Therefore, canine degenerative myelopathy is considered a differential diagnosis for medullary neoplasms, disc protrusion, and hip dysplasia, and since the clinical signs presented by the animals are similar in all these diseases, genetic testing plays an important role in diagnosis. In several dog breeds degenerative myelopathy was linked to the c.118G>A autosomal recessive variant in exon 2 of the superoxide dismutase 1 (SOD1) gene (SOD1:c.118G>A). In addition, the SOD1:c.118G>A variant in more than 124 breed dogs, suggests that this variant is widely spread and fixed in the species before the breeds' origin. However, there are few studies evaluating this variant in brazilian dogs, and none of them have evaluated it in the Brazilian Golden Retriever dogs. Therefore, this study aimed to evaluate the allele frequency of the SOD1:c.118G>A variant in Golden Retriever dogs from Brazilian kennels. Materials, Methods & Results: A total of 122 Brazilian Golden Retriever DNA samples were used in a PCR procedures with specific primers, previously described, to amplify a 779 base pairs amplicon containing the SOD1:c.118G>A variant in this study, and a non-template control reaction was performed to check possible contamination in the PCR preparation. The genotyping of the animals was performed by direct Sanger sequencing of PCR products that amplified a fragment containing the variant. Considering the 95% confidence interval, the sample size used in the present study was slightly larger than the minimum required to assess the allele frequency of SOD1:c.118G>A variant (122 versus 113 samples). All animals assessed in this study were clinically normal at the time of sampling and were identified as wild-type for the SOD1:c.118G>A variant. Therefore, no alleles of the pathogenic variant (A) were found in the studied population. Discussion: Although all animals assessed in this study were classified as wild-type, this study is the 1st report in Brazil to evaluate the prevalence of this variant in Golden Retriever dogs. The poor prognosis and inexorable progression of canine degenerative myelopathy force most owners to opt for early euthanasia of affected animals. Knowledge of the disease by owners and breeders, as well as the genotyping of their animals, may prevent the spread of the variant among lineages and also assist veterinarians in differential diagnosis and management of cases of canine degenerative myelopathy. The genetics of Brazilian Golden Retriever were mainly derived from USA bloodlines. With this in mind, we may speculate that the results observed in this study may be influenced by the lower prevalence of the SOD1:c.118G>A variant previously found in American Golden Retrievers. The results obtained in the present study, combined with previous studies that described the occurrence of this variant as rare in Golden Retrievers, lead us to speculate that this variant does not impact the Brazilian Golden Retriever dogs. [ABSTRACT FROM AUTHOR]

Background: Congenital myotonia is a genetic neuromuscular disorder characterized by delayed relaxation of the musculature following a strong contraction. Variants in the skeletal muscle chloride channel 1 gene (CLCN1) have been linked to this disorder across several species. The CLCN1_c.1775A>C, an autosomal recessive variant, was identified as a potential causative factor for congenital myotonia in New Forest Pony. While the CLCN1_c.1775A>C variant has been studied in different breeds of horses, it remains unexplored in Brazilian Quarter Horses. Therefore, this study aimed to assess the prevalence of the CLCN1_c.1775A>C variant among Brazilian Quarter Horses across various disciplines. Materials, Methods & Results: In this study, 96 DNA samples were obtained from athletic Brazilian Quarter Horses representing various disciplines, 24 each from cutting, reining, barrel racing, and bull-cacthing ("vaquejada"). DNA viability was assessed via PCR targeting the ß-actin gene. Subsequently, a previously described set of specific primers was employed to amplify the region encompassing the CLCN1_c.1775A>C variant. The resulting purified PCR products underwent Sanger direct sequencing, and their electropherograms were analyzed. Notably, none of the horses in this cohort were found to carry the CLCN1_c.1775A>C variant. The inbreeding coefficient (F) was calculated using pedigree data sourced from the 96 Quarter Horses according to Brazilian Quarter Horse Breeders Association records encompassing 4 generations. The average F value for the entire cohort was found to be 0.2%. However, when assessed across disciplines, the average F values varied, with cutting at 0.002 (0.2%), reining at 0.003 (0.3%), barrel racing at 0.0008 (0.08%), and bull-cacthing at 0.001 (0.1%), respectively. Notably, within this cohort, 48 horses were identified as inbred, exhibiting an average F of 1.5%. Discussion: Genetic variants associated with conditions such as hyperkalemic periodic paralysis, myosin heavy chain myopathy, and polysaccharide storage myopathy type 1 have been previously documented in Quarter Horses globally, including Brazil. However, as in the present study, the CLCN1 c.1775A>C variant was also not detected in American Quarter Horses affected by muscular disorders. Although this variant has been implicated as the cause of congenital myotonia in a New Forest pony, its correlation with cases of congenital myotonia in Quarter Horses has not been established yet. Although the inbreeding coefficient and the prevalence of endogamous horses observed in this study were lower compared to findings in other studies, the presence of inbreeding and shared ancestors within Quarter Horses lineages was evident. High rates of inbreeding may disseminate undesirable genetic variants, since popular stallions may improve the athletic performance of its progenies but also may transmit alleles with pathogenic variants, as seen in other genetic disorders in horses. Differently, since it was not observed in this group of evaluated Quarter Horses nor in other previous studies, it may be that the CLCN1 c.1775A>C is a 'de novo' variant related strictly to congenital myotonia in the New Forest pony. Nevertheless, it is imperative to highlight the potential for congenital myotonia to inflict significant harm upon horses. Investigations into new cases are essential to establish both clinical and etiological diagnoses, thereby enabling the assessment of the requisite preventive measures against this disorder. [ABSTRACT FROM AUTHOR]