Study On The Polymorphism Of Estrogen Receptor(ESR) Gene And Follicle-Stimulating Hormone β(FSHβ) Gene And The Coorelation With Reproduction Traits In Swine

Improving litter size is one of the major goals of pig breeding. The selection response is slow by phenotype selection because the heritability of litter size is low. Marker-assisted selection (MAS) could accelerate the selection response. MAS can be realized through detection of quantitative trait loci (QTL). QTL with moderate to large effect have been detected using genome scan. Another strategy to implement MAS is to identify mutations from genes with known biological functions.Rothschild et al. choose the estrogen receptor gene (ESR) as a candidate gene to study its relationship with litter size of large White pigs because steroid hormones and their receptors are essential in the process of reproduction. They found that a DNA fragment in ESR could have three genotypes (AA, AB, and BB) after digestion by PvuⅡand that the BB sows had a significantly higher litter size than those of the AA sows. Although subsequently there have been many reports on the relationship between ESR and the reproduction traits of pigs, the conclusions were often inconsistent. With regard to the association between ESR and the litter size of Erhualian pigs, Zhang et al. concluded that the relationship was not significant; but the results of Chen et al, Ding et al. and Meng and Liu were significant. The meta-analysis of Alfonso could not confirm which sows had larger litter size based on their respective ESR genotypes. Reports on the association between genes and traits could not be used directly in breeding schemes, because the genetic background could be different from the practical population.Li. et al. choose the Follicle-Stimulating Hormoneβ(FSHβ) as a candidate gene to study its relationship with litter size of pigs. Sequences analysis showed that there was an inserted mutation in FSHβgene of pigs. The length of the inserted fragment was 275bp, between + 809bp and + 810bp of the published sequences (D00621). According to the poly (A) with 17 adenines, the RNA polymerase III promoter structure and Alu I restriction enzyme site in the inserted fragment , it should be regarded as an Alu element .so it was assumed that the poly (A) structure in the inserted fragment should influence the pig litter size.ESR and FSHβgene were chosen as two candidate gene for production traits of swine. The polymorphism of ESR was detected by PCR-RFLP in pigs;the polymorphism of FSHβgene was detected by PCR in pigs;the extron 1 of ESR was detected by PCR-SSCP in pigs and the relationship between the polymorphism and reproduction traits was analyzed .The purpose of this article is to analyze the correlation between ESR,FSHβgenotypes and reproduction traits in the Songliao pig population and to determine the possibility of using ESR and FSHβin practice. The results were as follows:The allele frequencies of ESR,FSHβgenotypes were in Hardy-Weinberg equilibrium in Songliao pigs.Different genetypes of FSHβhad different effects on the size of litter by the order EF > FF > EE ; meanwhile , ESR by the order BB > AB > AA. With regard to the traits of TNB and NBA, BB sows were superior to sows of the other two genotypes, AA andAB, which did not exhibit significant differences between them.the BBsows had a significantly higher litter size than those of the AA sows. the BBsows had more 2.395 and 2.250 than those of the AA sows. the EEsows had more 2.274 than those of the EF sows.Neither of the allele frequencies of ESR,FSHβgenotypes has effect on pig growth (include litter weight of 20 days,litter weight of 60 days and litter weight born) and teat number.In Junmu pigs the allele frequencies of ESR,FSHβgenotypes were in Hardy-Weinberg equilibrium. The frequency of allele A and F was 0.78. For FSHβ,with regard to the traits of NBA, EE sows were superior to sows of the FF.The ESR havn't effect on TNB and NBA.Neither of the allele frequencies of ESR,FSHβgenotypes has effect on pig growth (include litter weight of 20 days,litter weight of 60 days and litter weight born) and teat number.In Songliao pigs, the combined genetype AAEF means more litter size than other gene type. As a result, the sows with gene type AAEF have 2.425 piglets of the total number born more than the sow with BBFF gene type.The AAEF have 2.2 piglets of number of born alive more than the sow with ABEF gene .meanwhile, The AAEF have 2.554 piglets of number of born alive more than the sow with BBFF gene . Neither of the allele frequencies of the combined genetype has effect on pig growth (include litter weight of 20 days,litter weight of 60 days and litter weight born )and teat number.An optimized standard PCR-SSCP protocol was employed to detect the 700bp fragement of exon1 of ESR gene. The results showed that there were no mutations.