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Association with litter size of new polymorphisms on ESR1 and ESR2 genes in a Chinese-European pig line

Gloria Muñoz1, Cristina Ovilo1, Jordi Estellé2, Luis Silió1*, Almudena Fernández1 and Carmen Rodriguez1

Author Affiliations

1 Departamento de Mejora Genética Animal, SGIT-INIA, 28040 Madrid, Spain

2 Departament de Ciència Animal i dels Aliments, UAB, 08193 Bellaterra, Spain

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Genetics Selection Evolution 2007, 39:195-206  doi:10.1186/1297-9686-39-2-195

The electronic version of this article is the complete one and can be found online at:

Received:14 July 2006
Accepted:31 October 2006
Published:17 February 2007

© 2007 INRA, EDP Sciences


The objective of this study was to search for polymorphisms in the coding region of the estrogen receptors 1 and 2 (ESR1 and ESR2 )and to analyze the effects of these variants and the well known intronic ESR1 Pvu II polymorphism on litter size in a Chinese-European pig line. We identified five silent single nucleotide polymorphisms (SNP) in the ESR1 cDNA: c.669T > C (exon 3), c.1227C > T (exon 5), c.1452C > T (exon 7), c.1665T > C and c.1755A > G (exon 8). One pair of these SNP (c.1665T > C and c.1755A > G) co-segregated in the analyzed line, and the SNP c.669T > C showed the same segregation pattern as the Pvu II polymorphism. These polymorphisms were tested in this study, although the c.1452C > T SNP within exon 7 was not analyzed due to its low informativeness. In the ESR2 cDNA, one missense SNP was found within exon 5, which caused an amino acid substitution in the coded protein: "c.949G > A (p.Val317Met)" and was tested on sow litter size. Information on 1622 litter records from 408 genotyped sows was analyzed to determine whether these SNP influenced the total number of piglets born (TNB) or the number of born alive (NBA). The polymorphisms ESR1: [Pvu II; c.669T > C], ESR1: [c.1665T > C; c.1755A > G] and ESR2: c.949G > A showed no statistically significant association with litter size. However, the ESR1: c.1227T allele was significantly associated with TNB. The additive substitution effect was estimated to be 0.40 piglets born per litter (P < 0.03), and no dominance effects were observed. This SNP could be useful in assisted selection for litter size in some pig lines, as a new genetic marker in linkage disequilibrium with the causative mutation.

estrogen receptor genes; polymorphisms; pig; litter size


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