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United States Department of Agriculture

Agricultural Research Service

Research Project: IMPROVING SOW LIFETIME PRODUCTIVITY IN SWINE

Location: Reproduction Research

Title: Variation in the coding and 3’ untranslated regions of the porcine prolactin receptor short form modifies protein expression and function

Authors
item Trott, Josephine -
item Freking, Bradley
item Hovey, Russell -

Submitted to: Animal Genetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 26, 2013
Publication Date: February 1, 2014
Citation: Trott, J.F., Freking, B.A., Hovey, R.C. 2014. Variation in the coding and 3’ untranslated regions of the porcine prolactin receptor short form modifies protein expression and function. Animal Genetics. 45(1):74-86.

Interpretive Summary: Improving sow lactation performance using management tools or different nutritional strategies is of current relevance to the swine industry. Inadequate milk production can impair survival rates and the pre- and post-weaning growth of piglets so there is a need for a better understanding of the hormonal regulation of milk production. The polypeptide hormone prolactin (PRL) regulates numerous physiological functions through the PRL receptor (PRLR). The most pronounced effects of PRL in pigs are its role in growth of the udder and milk production and in reproduction, but it also influences stress responses and behavior of the sow. This diversity of responses to PRL highlights the important role for the PRLR and its regulation. Results of this study revealed important differences in genetic variation for the short form version of the PRLR that leads to functional differences in expression and activity. Our analysis of the four short form haplotype variants revealed different functions and abilities to interact with the long form while still sharing similar affinity for prolactin itself. This study will lead to a more detailed understanding of genetic regulation of lactation performance in pigs.

Technical Abstract: The actions of prolactin (PRL) are mediated by both long (LF) and short isoforms (SF) of the PRL receptor (PRLR). Here, we report on a genetic and functional analysis of the porcine PRLR (pPRLR) SF. Three single nucleotide polymorphisms (SNPs) within exon 11 of the pPRLR-SF give rise to four amino acid haplotypes of the intracellular domain. We identified the dimorphic insertion of a short interspersed repetitive DNA element (PRE-1) along with 32 SNPs and four other insertion/deletion sites within the 3' untranslated region (UTR) of pPRLR-SF. The PRE-1 element reduced protein translation in vitro by 75%, whereas the combination of 10 SNPs and one insertion/deletion decreased translation by 50%. Full-length cDNAs for all four haplotypes of pPRLR-SF were cloned behind the elongation factor 1-alpha promoter and functionally analyzed in vitro. None of the haplotypes could initiate transcription from the ß-casein promoter, whereas all four were dominant negatives against PRL-activation of the pPRLR-LF. Two of the haplotypes completely inhibited pPRLR-LF activity at a four-fold excess, whereas the others required a six-fold excess to impart the same effect. The ligand binding affinities of the pPRLR-SF haplotypes did not differ. Expression of the pPRLR-SF increased linearly during gestation in the endometrium and was hormonally regulated in a tissue-specific manner in the mammary glands and uterus. In conclusion, we identified a PRE-1 and other SNPs in the pPRLR-SF 3' UTR that reduce protein expression and four haplotypes of the pPRLR-SF that suppress pPRLR-LF signaling and may differentially impact the phenotypic effects of PRL in vivo.

Last Modified: 9/22/2014
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