Candidate gene analysis for reproductive traits in two lines of rabbits divergently selected for uterine capacity.

The objective of this work was to analyze 3 functional candidate genes for reproduction in 2 lines of rabbits divergently selected by uterine capacity. Both lines were selected for 10 generations. The selection was then relaxed until the 17th generation, when it was compounded by 61 and 63 does of the High and Low lines, respectively. We sequenced the SCGB1A1 gene, which encodes the main protein secreted by the rabbit in the uterus and seems to play an important role in implantation. We found 6 SNP in the promoter region cosegregating in 2 haplotypes in both lines with similar frequency. We also analyzed IGF1 mRNA because of its effects on embryo development, but we did not find any polymorphism between individuals of the 2 lines. The third gene analyzed was the TIMP1, which encodes a protein involved in many biological processes related to reproduction. We determined the sequence of its promoter region and found 1 SNP (g.1423A>G) segregating with different frequencies in both lines (0.60 for allele A in the High line and 0.82 for allele G in the Low line). The association study performed in an F(2) population (n = 598) generated by the cross of the 2 lines of rabbits revealed that the AA genotype had 0.88 embryos more than the GG genotype at 72 h of gestation. The difference increased to 2.23 embryos at implantation, but no difference was found between genotypes at birth. These results suggest that TIMP1 could be a candidate gene for embryo implantation and embryo survival.