Resumen de Candidate gene for litter size and its components: progesterone receptor gene
The general objective of this thesis is to study the effect of the rabbit progesterone receptor (PGR) gene on litter size and its components using a F2 population from a cross between two divergent lines selected for uterine capacity (UC) during 10 generations differing mainly in embryo survival.
In order to achieve better information to identify a physiological candidate gene, it was useful to determine the time of gestation in which differences in early embryo survival and development appeared. A total of 162 females from the High line, selected to increase UC, and 133 females from the Low line, selected to decrease UC, were slaughtered at 25, 48 and 62 h of gestation. Both lines had similar ovulation rate and fertilization rate at the early stages of gestation. The High line had a higher embryo survival than the Low line at 62 h of gestation (0.57 embryos), and also more embryonic stage of development at 48 and 62 h of gestation, showing a higher percentage of early morulae (10%) and higher percentage of compacted morulae (16%), respectively.
A total of 598 intact F2 females were obtained crossing 3 bucks of the High line with 13 unilaterally ovariectomized (ULO) does of the Low line and crossing 3 bucks of the Low line with 5 ULO does of the High line. The rabbit PGR gene was selected as candidate gene because progesterone is related to reproductive traits and also because knockout mice showed reproductive abnormalities. A 3702 bp sequence of the rabbit PGR gene was obtained from parental animals and five single nucleotide polymorphism (SNP) were found; a SNP was found in the promoter region, 2464G>A, three SNPs in the 5¿UTR exon 1 and a silence SNP in the exon 7. The SNPs found in the promoter region and in the 5¿UTR were cosegregating in two haplotypes. A PCR-RFLP method was developed for genotyping the 2464G>A SNP in the promoter region.
