Orientador: José Paes de Oliveira Filho / Resumo: O estudo das doenças de origem genética em animais domésticos se torna cada vez mais relevante, sobretudo em cães, uma vez que estes animais podem servir como modelos experimentais para certas doenças em humanos. Além disso, o reconhecimento clínico de algumas destas enfermidades pode ser um entrave ao Médico Veterinário e em algumas ocasiões o teste genético que confirmaria a etiologia não está disponível no país. A Nefropatia Familiar (FN) causada pela mutação c.115A>T no gene colágeno tipo 4α4 (COL4A4), e a Atrofia Progressiva da Retina (prcd-PRA), causada pela mutação c.5G>A no gene da degeneração cone-bastonete progressiva (PRCD), se destacam entre as principais enfermidades hereditárias de origem genética que acometem cães da raça Cocker Spaniel Inglês (CSI). Até o momento a prevalência destas enfermidades nesta raça não havia sido verificada no Brasil, sendo assim, o objetivo deste estudo foi avaliar a frequência alélica destas mutações no CSI. Para tanto, foram genotipados 220 e 216 CSI para a prcd-PRA e FN, respectivamente. Fragmentos do DNA, contendo cada uma das mutações, foram amplificados por reação em cadeia da polimerase e submetidos ao sequenciamento gênico direto. A frequência alélica da mutação c.115A>T no gene COL4A4 foi de 0,9% e da mutaçao c.5G>A no gene PRCD foi de 25,5%. Tais valores enfatizam a importância da realização dos testes de genotipagem nos cães da raça CSI como método de diagnóstico precoce principalmente para a orientação dos acasalamentos v... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The study of genetic diseases in domestic animals has become more relevant, especially in dogs, once these animals can serve as experimental models in the study of some human genetic diseases. Besides, these diseases can be hard to recognize on their clinical signs by the practitioners, and the genetic tests that can confirm them are usually available only abroad. Familial Nephropathy (FN) due to the mutation c.115A> T in the 4α4 collagen gene (COL4A4), and Progressive Retinal Atrophy (prcd-PRA) due to the mutation c.5G> A in the progressive rod cone degeneration gene (PRCD), are important genetic diseases of English Cocker Spaniel dogs (ECS) dogs. Since the prevalence of these diseases wasn’t verified in Brazil so far, this study aims to evaluate the allelic frequencies of the mutations c.115A>T in the COL4A4 gene and c.5G>A in the PRCD gene in English Cocker Spaniel dogs. For that, purified DNA from blood samples or buccal swab from 220 and 216 ECS for prcd-PRA and FN, respectively. DNA fragments with the mutation region were amplified by polymerase chain reaction and submitted to direct genomic sequencing. The allelic frequency of the mutation c.115A>T in the COL4A4 gene was 0.9% and the c.5G>A in the PRCD gene was 25.5%. The results in this study emphasizes the importance to realize the genotyping test in ECS as an early diagnostic test, not only for trying an improvement of the affected dogs’ life quality but also for breeding orientation to avoid clinical cases of the d... (Complete abstract click electronic access below) / Mestre

Progressive rod-cone degeneration (PRCD) is the late form of progressive retinal atrophy (PRA). It is an autosomal recessive hereditary retinal defect. This disease in dogs is consistent with one form of retinitis pigmentosa (RP) in humans. Phenotypic manifestations are identical and it is known to be an identical causal mutation. A study of this defect in dogs could also explain a lot in human medicine. The gene for PRCD was mapped in the region of centromer of the canine chromosome 9 (CFA9). In this thesis, genotyping of 120 dogs of different breeds and age was performed. Most represented a breed of English Cocker Spaniel which is predisposed to the disease. Analysis PRA-PRCD was performed by molecular genetic methods PCR-RFLP and the horizontal agarose electrophoresis. Genotypes were determined on the basis of different fragment lengths. The normal allele was 396 bp in length and the mutated allele had a length of 116 bp. Presence of mutated allele was only detected in 25 heterozygotes carriers which were usually breeds with this predisposition. Frequency of the mutated allele was 10.4 %. In the selected population 20.8 % of heterozygotes were represented. The results of the study show approximately one fifth of the tested dogs are heterozygous carriers. Findings of other studies confirm there are generally more heterozygotes than homozygotes in which the disease is manifested during life. However, if this fact is not clearly taken in consideration, the number of sick dogs can rapidly increase during short period of time. In the future, it would be appropriate to adopt measures which would definitely eliminate the occurrence of the mutated allele. These measures could include genetic tests that reliably reveal hidden carriers (heterozygotes) in predisposing breeds. Heterozygotes may increase the representation of this allele in the population. This leads to an increase in the number of diseased animals.

<p>  </p> <p>With the discovery and treatment of any disease comes the important question of its genetic prevalence. This is especially important for animals under strict breeding control, such as dogs, because this can provide essential information regarding breeding pair decisions. Thus, the focus of this thesis is to investigate the genetic prevalence of three different diseases: 1) Factor VII Deficiency (FVIID), 2) Collie Eye Anomaly (CEA), and 3) Progressive Rod-Cone Degeneration-Progressive Retinal Atrophy (prcd-PRA). Factor VII Deficiency (FVIID) is a clotting disorder observed in both humans and dogs, characterized by impeded function of the Factor VII protein. In dogs, FVIID is caused by a single nucleotide substitution (c.407G>A) in the <em>F7 </em>gene. This mutation, identified in a colony of research Beagles, is also present in dogs with a wide variety of distantly-related breed backgrounds and in mixed-breed dogs, suggesting an ancient, ancestral origin. Given the relatively common presence of this variant, it was hypothesized that this genetic mutation could be contributing to excessive bleeding in canine autopsy cases that could not be attributed to typical causes. DNA from formalin-fixed paraffin-embedded tissues (n = 67 cases) were Sanger sequenced for the FVIID c.407G>A mutation, and all were determined to be homozygous wild-type. Therefore, the tested variant is not associated with the unexplained bleeding in these cases, and it is not a logical diagnostic test to apply to similar cases in the future.</p> <p><br></p> <p>CEA and prcd-PRA are ophthalmic genetic diseases of concern often included in commercial genetic testing panels. A large dataset spanning 15+ years provided by a commercial partner company (OptiGen/Wisdom Panel, Kinship) encompassed dogs tested for the CEA-associated <em>NHEJ1</em> deletion (n = 33,834 dogs) and the prcd-PRA causal mutation in <em>PRCD</em> (n = 86,667 dogs). Disease trends were observed graphically and analyzed with Chi-square goodness-of-fit testing and regression modeling for disease status and genotype classification. Both diseases had a statistically significant change in genotype frequencies from the first year of data to the last; both diseases also had a negative association between progression of time and overall probability of a dog being disease-positive or a carrier/heterozygous. This suggests that genetic testing results are being incorporated into breeding decisions, although affected dogs were still being identified by the end of this study. Different breeds, AKC groups, FCI groups, genetic clades, and geography were also investigated to determine impact on overall disease trend. </p>