FUNCTIONAL ANALYSIS OF GENES FOR REPRODUCTIVE CHARACTERISTICS IN PIGS: FROM GWAS TO POST-GWAS

Reproductive characteristics, such as the number of teats, uniformity and litter size, are essential for animal breeding programs due to their importance to the production chain, as they influence the maternal ability of sows and can affect the number of weaned piglets. Our objective was to identify candidate genes associated with reproductive traits in pigs, through a systematic review using GWAS data, and to build networks of biological processes and Gene-TFs networks from the identified genes in order to highlight the most candidate genes for litter size, uniformity and number of teats. The systematic review considered peer-reviewed articles, using descriptors related to the characteristics evaluated, and selected based on eligibility criteria. Fourteen articles were selected and classified into groups for functional analysis of gene networks. 2077 candidate genes were identified from the systematic review. After combining with the list of genes associated with the structural variants present in the 5'UTR and/or coding region, 306 genes remained that were used to construct the networks of biological processes and TFs gene networks, highlighting processes associated with litter size. (e.g., ionotropic glutamate receptor signaling pathway and blastocyte growth) and teats number (e.g., growth hormone receptor, regulation of the BMP - Bone Morphogenetic Proteins signaling pathway and blood vessel proliferation). Three most candidate genes for litter size trait (<em>GRID2</em>, <em>GRIK3</em> and <em>PALB2</em>) and six most candidate genes (<em>GHR, IFT80,</em> <em>FSTL3, SKOR1, SMURF1</em> and <em>AKT3</em>) for teats number were prioritized. Transcription factors associated with candidate genes were also identified for litter size (<em>PALB2</em> and <em>GRID2</em>) and teat number (<em>RIN, LTBP2</em> and <em>COL6A6</em>). Thus, from this study, it is suggested that the genes and TFs presented in this study play an important role in the characteristics studied, being important for genetic studies and animal breeding, because their regulatory genetic mechanisms are involved in the expression phenotypic characteristics of these traits, influencing the reproductive performance and pigs productivity. The discovery of these genes may bring new considerations to the current knowledge of the genetic architecture of these traits, since the markers associated with these genes can be assigned higher weights in genomic selection and validated in specific populations.