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.