Prolactin Expression in the Baboon (Papio hamadryas) Eye

SIMPLE SUMMARY: In primates, prolactin (PRL) is expressed in the pituitary gland; however, the extra-pituitary expression has been reported, including in the eye. The baboon is an excellent animal model for understanding the possible role of this hormone in the eye. The objective of this study was to detect PRL and its receptor expression in the eye tissues of fetal and adult baboons. Moreover, we performed PRL gene sequencing and a phylogenetic analysis to identify the evolutionary divergence in human and primate genes of PRL. We detected PRL and PRLR expression in all retinal cell lineages in fetal and adult baboons. No expression of these genes was detected in the cornea, lens, sclera, and iris. PRL and PRLR fit the hypothesis of evolutionary purifying gene selection. According to our findings, PRL has a role in prenatal and post-natal homeostasis of the baboon eye. We suggest that the hormone triggers autocrine and paracrine-specific functions in eye development. ABSTRACT: Prolactin (PRL) is a hormone expressed in lactotrophs cells of the pituitary gland in primates. Extra pituitary expression of PRL has been reported, including the eye; however, expression in the developing eye of primates is limited. The aim of the study was determining the expression of PRL and PRL receptor (PRLR) (mRNAs and proteins) in adult and fetal baboon (Papio hamadryas) ocular tissues. Methods: We analyzed PRL and PRLR in baboon eyes tissues by immunofluorescence. The mRNAs of PRL and PRLR were detected by RT-PCR, cDNA was cloned, and sequenced. Furthermore, we performed a phylogenetic analysis to identify the evolutionary forces that underlie the divergence of PRL and PRLR primate genes. Results: We observed the expression of PRL and PRLR (mRNAs and proteins) in all retinal cell lineages of fetal and adult baboon. PRL and PRLR fit the hypothesis of evolutionary purifying gene selection. Conclusions: mRNA and protein of PRL and PRLR are expressed in fetal and adult baboon retinal tissue. PRL may trigger autocrine and paracrine-specific actions in retinal cell lines.