Polymorphism of OPN and AREG Genes in Relation to Transcript Expression of a Panel of 12 Genes Controlling Reproduction Processes and Litter Size in Pigs

Abstract

The aim of this study was to define the transcript expression of 12 genes, identify new polymorphisms in selected 2 genes and to estimate the association between the level of expression, gene polymorphism and litter size in sows. Two groups of sows were selected: 71 crossbred sows and 328 purebred sows. For transcript analysis endometrial tissue samples were collected, while blood was sampled for the purpose of DNA polymorphism analysis. For all animals data on litter size and weaned piglets were obtained. Transcript analysis of 12 genes was performed in the uterine endometrium of sows in the luteal and follicular phases. Eight out of 12 genes showed higher mRNA expression levels during the luteal phase (AREG, FABP3, IL1A, ITGAV, ITGB3, NMB, OPN, RBP4). In turn, higher expression levels in the follicular phase were observed for 4 genes (IL1B, PPARG, S100A8, SELL). Analysis of six new polymorphic sites within the OPN and AREG genes revealed the highest heterozygosity for OPNe6_Knoll, OPNp3_617 and AREGe2_317 polymorphisms and the lowest heterozygosity in the AREGe3_561 locus. Association analyses concerning transcript expression levels of the 12 genes and the OPN and AREG genotypes in the two groups of sows showed a significant relationship between the IL1A, ITGB3 transcript expression and the OPNe7_603 genotype also between OPNp3_617 genotype and ITGB3 transcript expression. With regard to the litter size and the number of weaned piglets a significant relation with the OPNp3_617, OPNe6_462 and AREGe2_317 genotypes was observed only in the purebred sows. Transcript expression of the genes encoding osteopontin and amphiregulin in the uterus of the sows affect reproductive traits by preparing the uterus for embryo reception.

A Missense p.Q>R234 Mutation in the Osteopontin Gene Is Associated With the Prolificacy of Iraqi Awassi Ewes

“…Recently, there seems to be a significant relationship between purebred sows carrying the OPNe6-462 and OPNp3-617 genotypes and piglet size and the number of weaned piglets. 17 Numerous in silico analyses confirmed the damaging effects of the p.Q>R234 SNP on the structure, biological functions, and stability of OPN; for example, a deleterious nsSNP may adversely affect OPN’s ability to perform its function. Consequently, the greater frequency of p.Q>R234 results in damaged OPN synthesis leading to lower prolificacy of Awassi ewes.…”

“… 14 Moreover, many variations have been identified in the OPN ( SPP1 ) gene with production traits in cattle, 15 and reproductive traits and litter size in pigs. 13 , 16 , 17 Based on the above literature review, very few studies have been conducted on genetic polymorphisms in the OPN gene in relation to their association with cattle prolificacy, and to the best of our knowledge, no studies have been conducted regarding their association with sheep prolificacy.…”

Retrotransposon Insertion Polymorphisms (RIPs) in Pig Reproductive Candidate Genes

“…Earlier studies by Terman [ 46 ] indicated that PRLR significantly affects the litter size of pigs; however, its association signals of variants to these genes with litter size are inconsistent among different lines or groups. Some studies have also reported that non-synonymous SNPs of the OPN gene had an association with litter size traits in pigs [ 47 , 48 , 49 ]. With respect to the reproductive traits in the Large White pig breed, data from the present study showed no significant difference while determining the statistical analysis based on the RIP-VMP1-12, RIP-PRLR-6, and RIP-OPN-1 polymorphic types.…”