Comparative genomics reveals tissue-specific regulation of prolactin receptor gene expression

Authors: SCHENNINK, ANKE - University Of California; TROTT, JOSEPHINE - University Of California; MANJARIN, RODRIGO - University Of California; LEMAY, DANIELLE - University Of California; Freking, Bradley - Brad; HOVEY, RUSSELL - University Of California

Submitted to: Journal of Molecular Endocrinology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/30/2014
Publication Date: 2/1/2015
Publication URL: http://handle.nal.usda.gov/10113/61911
Citation: Schennink, A., Trott, J.F., Manjarin, R., Lemay, D.G., Freking, B.A., Hovey, R.C. 2015. Comparative genomics reveals tissue-specific regulation of prolactin receptor gene expression. Journal of Molecular Endocrinology. 54(1):1-15. DOI: 10.1530/JME-14-0212.

Interpretive Summary: Efficient sow lactation performance is a critical component of the production cycle in the swine industry. Inadequate milk production can impair survival rates and the pre- and post-weaning growth of piglets. Therefore, a better understanding of the hormonal cues that regulate milk production is needed. The polypeptide hormone prolactin (PRL) regulates numerous physiological functions through the PRL receptor (PRLR). Understanding the responsiveness of various tissues to PRL during various physiological states requires an accurate understanding of how the PRLR gene is processed to regulate its expression in different tissue or stages of reproduction. We have identified nine novel promoters that facilitate tissue-specific regulation of PRLR expression and splicing activity in pigs. Through a comparative genomics approach we have also identified a tissue-specific PRLR promoter in humans. Results of this study provide the most detailed analysis of regulation of PRLR gene splicing and expression in different pig tissues to date. This study will lead to improved lactation performance in pigs through a better understanding of how the PRLR gene is processed and regulated.

Technical Abstract: Prolactin (PRL), acting via the prolactin receptor, fulfills a diversity of biological functions including the maintenance of solute balance and mineral homeostasis via tissues such as the heart, kidneys and intestine. Expression and activity of the prolactin receptor (PRLR) is regulated by various tissue-specific mechanisms across a broad range of species. Herein we report a wide scale analysis of PRLR 5’ transcriptional regulation across PRL target tissues in the pig. Beyond ubiquitous expression of transcripts expressed from the widely conserved exon 1 (pE1), we identified an additional nine first exons of the porcine PRLR (pPRLR) gene that are alternatively spliced. Notably, we find that exon 1.5 is the most highly expressed transcript in the heart, while exon 1.3 is primarily expressed in the kidney and small intestine with lower levels in the liver and virtually no expression detectable in any other tissue. Consistent with a role for pPRLR during pregnancy, expression of exon 1.3 expression increased in the kidneys during gestation, and was most abundant in the renal cortex. A comparative analysis revealed that human PRLR splice variants are transcribed from the promoter of a homologous exon 1.3 in humans, which is also principally expressed in the kidneys and small intestine. Alignment of the promoters for six homologs of porcine exon 1.3 revealed significant conservation of the proximal promoter sequences including putative binding sites for hepatocyte nuclear factor 1 (HNF1) and specificity protein 1 (Sp1). Together, these results highlight the diverse regulation of PRLR gene expression and highlight that the limited understanding of how PRL acts on known target organs such as heart, kidney and small intestine may be conferred by tissue-specific expression of the PRLR.