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.
Keywords: PRE-1; dominant negative; short interspersed repetitive element; single nucleotide polymorphisms.
© 2013 Stichting International Foundation for Animal Genetics.