Originally published as Genetics Published Articles Ahead of Print on September 14, 2008.

Genetics, Vol. 180, 1699-1705, November 2008, Copyright © 2008
doi:10.1534/genetics.108.090779

Identification of Single-Nucleotide Polymorphism in the Progesterone Receptor Gene and Its Association With Reproductive Traits in Rabbits

R. Peiró*,1, M. Merchán{dagger}, M. A. Santacreu*, M. J. Argente{ddagger}, M. L. García{ddagger}, J. M. Folch{dagger} and A. Blasco*

* Instituto de Ciencia y Tecnología Animal, Universidad Politécnica de Valencia, 46071 Valencia, Spain, {dagger} Departament de Ciència Animal i dels Aliments, Universitat Autònoma de Barcelona, 08193 Bellaterra, Spain and {ddagger} Departamento de Tecnología Agroalimentaria, Universidad Miguel Hernández de Elche, 03312 Orihuela, Spain

1 Corresponding author: Instituto de Ciencia y Tecnología Animal, Universidad Politécnica de Valencia, P. O. Box 22012, 46071 Valencia, Spain.
E-mail: ropeibar{at}dca.upv.es

A total of 598 F2 does from a cross between the high and low lines selected divergently for uterine capacity during 10 generations were used in a candidate gene analysis. The presence of major genes affecting the number of implanted embryos and uterine capacity has been suggested in lines divergently selected for uterine capacity. Uterine capacity is a main component of litter size. The progesterone receptor gene was tested as a candidate gene to determine whether polymorphisms explain differences in litter size and its components. Fragments of the promoter region and exons 1–8 were amplified and sequenced. One SNP was found in the promoter region, 2464G>A, three SNPs in the 5'-UTR exon 1, and a silence SNP in exon 7. The first four SNPs were segregated in two haplotypes. The allele G found in the promoter region was found in 75% of the high-line parental animals and in 29% of the low-line parental animals. The GG genotype had 0.5 kits and 0.5 implanted embryos more than the AA genotype. At 48 hr of gestation, the difference in early embryo survival and embryonic stage of development was small. However, at 72 hr of gestation, the GG genotype had 0.36 embryos more than the AA genotype and also had a more advanced embryonic stage of development, showing a lower percentage of compacted morulae and a higher percentage of blastocysts. The difference in litter size between the GG and GA genotypes was similar to the difference found between homozygote genotypes; however, differences in implanted embryos, early embryo survival, and embryo development were not detected between the GG and GA genotypes.