Estudo de associação ampla do genoma (GWAS) para a característica lábio leporino em bovinos da raça Gir Leiteiro

Abstract

Brazil has the largest cattle herd in the world and the genetics of the Gir breed are present in more than 80% of dairy herds, due to their special physiological features. Due to the high use of genetically superior animals, diseases related to narrow genetic base may become more frequent. The cleft lip is a congenital alteration characterized by the failure to close the facial processes, which prevents proper feeding of the animal, in addition to devaluing the affected animal and its herd. Genome wide association studies (GWAS) can help understanding the inheritance and molecular mechanisms involved in this undesirable trait. Thus, the aim of this work was to identify genomic regions and candidate genes for cleft lip condition in Gir dairy cattle. Samples of case and control animals were sent by producers who participate in the Brazilian Dairy Gir Breeding Program. GWAS procedure was used to analyse 16 animals with cleft lip phenotype (case group) and 48 animals displaying healthy phenotype (control group) and less related to the case group, defined by a matrix of genomic similarity. DNA was extracted using chloroform phenol methodology and evaluated by nano volume spectrophotometry. All samples were subjected to SNP array analysis thorugh the BovineHD Genotyping BeadChip. Genotype quality control was performed using the Golden Helix SVS 7 computational package, which removed non-autosomal markers with call rate<95% minimum allele frequency (MAF) <2% and HardyWeinberg equilibrium <10-6 . GWAS analyses were performed using the additive and dominant models in the same data set and the results were displayed in Manhattan plots. Genomic regions where significant results were obtained were explored to detect candidate genes located within or near the mapped genomic regions. We were able to find 265 significant SNPs distributed into 100 genomic regions, in which 35 candidate genes associated with cleft labyrinth were identified, providing information for future research on the cleft lip condition in cattle.