Novel Polymorphisms in Porcine 3′UTR of the Leptin Gene, Including a Rare Variant within Target Sequence for MIR-9 Gene in Duroc Breed, not Associated with Production Traits

The leptin gene (LEP) is considered as a functional candidate for production traits in livestock due to its crucial role in energy homeostasis. Because polymorphisms in regulatory sequences may affect gene expression, we searched for them in the 3 ' UTR of LEP and analyzed their association with production traits. Four breeds and a composite line were studied. In the Polish Landrace and Polish Large White breeds, 8 SNPs and 1 indel were observed; whereas, in the Duroc breed, 9 specific SNPs were found. Pietrain and Line 990 were monomorphic. One SNP (g.+168C>T), observed in the Duroc breed only, was located within a target site for microRNA (miR-9). Association studies showed a weak association between one SNP (c.+846C>T) and abdominal fat weight in the Polish Landrace only. Thus, we concluded that contribution of polymorphisms in the 3 ' UTR to phenotypic variability of pig production traits is marginal. Moreover, we presented an overview of known polymorphisms (128) in the pig leptin gene.