A candidate gene approach to identify genes predisposing for the autoimmune disease canine lymphocytic thyroiditis (CTL)

University essay from SLU/Dept. of Animal Breeding and Genetics

Abstract: The overall aim with this project is to apply a candidate gene approach to identify genes predisposing for the autoimmune disease, canine lymphocytic thyroiditis (CLT). Individuals clinically diagnosed either as CLT-affected or as healthy non-affected controls were analyzed from two birth cohorts of the breeds Giant Schnauzer and Hovawart, breeds that both has high incidence of CLT. Two different genes were evaluated for their potential involvement in CLT disease aetiology. Selection of the candidate genes was based on their confirmed role in both human and mouse as genetic risk factors in thyroid autoimmune disease. Firstly, to evaluate whether certain DLA-DRB1 Major Histocompatibility complex (MHC) class II exon 2 genotypes predispose for the development of CLT, cloning and sequencing of DLA-DRB1 exon 2 PCR products were performed. Secondly, studies of the gene encoding cytotoxic T-lymphocyte antigen 4 (CTLA-4) were performed using single nucleotide polymorphism (SNP) analysis and microsatellites. Nucleotide sequence analysis of the cloned DLA-DRB1 alleles will allow us to evaluate whether certain DRB1 alleles are predisposing for CLT [4]. A microsatellite analysis of CTLA-4 strongly suggested that CTLA-4 may be excluded as a gene predisposing for CLT in Giant schnauzer, with a chi-square value of 1.96 with three degrees of freedom. For a Chi square to be significant for three degrees of freedom it should be greater than or equal to 7.82. The P-value was 0.58, which indicates no statistical significance in the results. However, additional CLT-affected individuals and healthy controls must be analysed to obtain conclusive results.

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