| dc.description.abstract | The economic importance of improving genetically feed efficiency (FE) has been recognized
for over 40 years. Functional analysis can be relevant to reveal the action and interaction of all
genes and improve the understanding of the genetic mechanisms evolved in the phenotypic
expression of FE. The objective was to carry out a systematic review using data from GWAS
that evaluated FE in species of productive interest and to identify candidate genes relevant to
FE shared among the different species. In addition, to reinforce the importance of systematic
reviews in the discovery of markers associated with FE that can be useful to validate findings
of studies in a specific population. The search for articles for a systematic review was carried
out on the Pubmed and Google Scholar platforms, using 180 keyword models and the papers
were selected based on the eligibility criteria. To recover the positional candidate genes
associated with the markers and / or window, the assembly of the current genome of each
species was considered. The identification of the chosen candidate genes was carried out using
the approaches where the genes were prioritized by the principle of “guilt by association” and
meta-analysis (GUILDify and ToppGene software, respectively). 22 articles were selected in
the systematic review that described the information of 1.886 markers. The gene annotation
process resulted in 3.227 positional candidate genes annotated, simultaneously, for all species
(660 cattle, 870 chickens, 1,662 pigs and 35 sheep). A relevant point is that 172 positional
candidate genes were shared by at least two different species and were used to identify whether
any of these genes would be prioritized as a functional candidate gene. The top 100 ranked
genes obtained in the GUILDify analysis were used to build a trained list of genes. The
ToppGene analysis resulted in 122 significant genes and 17 genes were automatically
prioritized because they were already on the trained list. In this way, 139 functional candidate
genes for FE were identified. Five genes shared between the species of productive interest were
prioritized as functional candidate genes: SOX17, PENK, GRM5, CTNND1, KRAS, therefore,
they should be considered relevant genes for EA. The list of functional candidate genes found
in this study, is composed of some genes that play crucial roles in biological processes
associated with immune response, these results corroborate that food efficiency is related to the
immune response. In addition, our results show that the regulatory genetic mechanisms
involved in the phenotypic expression of feed efficiency, in fact, are affected by genes whose
functions are involved in the rate of growth of animals. The discovery of functional candidate
genes shared between different species, may bring new considerations to the current knowledge
of the genetic architecture of EA, since the markers associated with these genes can be attributed
with higher weights in genomic selection and validated in populations specific information. | |
