Estudo de associação genômica ampla (GWAS) para características de carcaça mensuradas por ultrassonografia em bovinos da raça Nelore

Abstract

The Nelore breed (Bos taurus indicus) is used on a large scale in Brazilian herds, however, Zebu animals have lower levels of fat in the carcass. This is due to the impasse in the selection of carcass characteristics, as these are often post-mortem measures, in addition to the high costs and difficulties in measuring. With the inclusion of genomics, the selection process, as well as studies of broad genomic association (GWAS) for the identification of genomic regions involved in the expression of these characteristics, became simpler. With this, the objective was to perform GWAS for the characteristics of subcutaneous fat thickness (EGS), fat thickness in the sirloin (EGP8), and finishing (ACAB), in order to identify genomic regions of greater effects, candidate genes, and yet, check their biological functions. For this, information from 1440 animals was used, all with ultrasound records and genotyped with the GGP-Indicus 35K panel. The analyzes were performed using the single-step GWAS (ssGWAS) method with the BLUPF90 family programs, which calculated the variations for genomic windows containing 10 consecutive single nucleotide polymorphisms (SNPs), and later, the regions that obtained more than 0, 5% of the total additive genetic variance was used to examine the candidate genes. After the identification of candidate genes by the ENSEMBL database, analyzes of genetic ontology (GO, PANTHER) and gene connection networks (REVIGO) were carried out, to assess which biological pathways the genes acted on, and also, the connection of these genes under each characteristic addressed. The main genes of EGS (TBL1XR1, AHCYL2, SLC4A7, AADAT, VPS53, IDH2, and ETS1), EGP8 (GSK3β, LRP1B, EXT1, GRB2, SORCS1, and SLMAP) and ACAB (GSK3β, LRP1B, EXT1, S1, EXT1, S1, and APAF1), these may be linked to fat deposition. The gene enrichment analysis revealed processes that can directly influence the characteristics studied, some of these genes belong to pathways related to the metabolism of lipids, polysaccharides, carbohydrates, lipid homeostasis, and cholesterol, in addition to others that may influence the composition of EGS, EGP8, and ACAB. The results reported here, will help in understanding the mechanisms that form the aforementioned characteristics, in addition, several of the identified genomic regions pointed out processes related to fat deposition, such processes may be useful for future genomic studies in Nellore cattle.