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

The prolactin receptor: A cross-species comparison of gene structure, transcriptional regulation, tissue-specificity, and genetic variation

The conserved and multifaceted functions of prolactin (PRL) are coordinated through varied distribution and expression of its cell-surface receptor (PRLR) across a range of tissues and physiological states. The resultant heterogeneous expression of PRLR mRNA and protein across different organs and cell types supports a wide range of PRL-regulated processes including reproduction, lactation, development, and homeostasis. Genetic variation within the PRLR gene also accounts for several phenotypes impacting agricultural production and human pathology. The goal of this review is to highlight the many elements that control differential expression of the PRLR across tissues, and the various phenotypes that exist across species due to variation in the PRLR gene.

Effects of Parental Experience and Age On Expression of Prolactin, Vasoactive Intestinal Peptide and Their Receptors in a Biparental Bird (Columba Livia)

As animals gain parental experience, they often show more rapid and efficient parental care responses that likely improve offspring survival and fitness. Changes in circulating hormones that underlie reproductive behaviors, including prolactin, have been found to correlate with parental experience in birds and mammals. Altered responsiveness to prolactin in key behavioral centers of the brain may also underlie the effects of experience on parental behaviors. Further, experience may also affect responsiveness to prolactin stimulatory hormones, such as hypothalamic vasoactive intestinal peptide (VIP). While experience has been shown to upregulate neural prolactin receptors and responsiveness in rodents, its effects on prolactin receptor gene expression remain unstudied in birds. To address this, we examined gene expression of pituitary prolactin, hypothalamic prolactin receptors in the preoptic area, hypothalamic VIP, and pituitary VIP receptors in both sexes of the biparental rock dove (Columba livia) when birds were not actively nesting. As age and parental experience are often confounded (i.e.,experienced parents tend to be older than their inexperienced counterparts), we measured gene expression in birds of varying combinations of age (0.6-3 years) and prior reproductive experience (0-12 chicks raised). We found that increasing experience with chicks correlated with lower PRLR expression in the preoptic area, and age correlated with lower VIP expression in birds of both sexes. Pituitary PRL and VIPR expression was not associated with parental experience or age. These results suggest there may be persistent effects of experience and age on neural responsiveness to, and regulation of, prolactin in birds.

The genetic basis for ecological adaptation of the Atlantic herring revealed by genome sequencing

Ecological adaptation is of major relevance to speciation and sustainable population management, but the underlying genetic factors are typically hard to study in natural populations due to genetic differentiation caused by natural selection being confounded with genetic drift in subdivided populations. Here, we use whole genome population sequencing of Atlantic and Baltic herring to reveal the underlying genetic architecture at an unprecedented detailed resolution for both adaptation to a new niche environment and timing of reproduction. We identify almost 500 independent loci associated with a recent niche expansion from marine (Atlantic Ocean) to brackish waters (Baltic Sea), and more than 100 independent loci showing genetic differentiation between spring- and autumn-spawning populations irrespective of geographic origin. Our results show that both coding and non-coding changes contribute to adaptation. Haplotype blocks, often spanning multiple genes and maintained by selection, are associated with genetic differentiation.

Zinc Finger Homeodomain Factor Zfhx3 Is Essential for Mammary Lactogenic Differentiation by Maintaining Prolactin Signaling Activity

The zinc finger homeobox 3 (ZFHX3, also named ATBF1 for AT motif binding factor 1) is a transcription factor that suppresses prostatic carcinogenesis and induces neuronal differentiation. It also interacts with estrogen receptor α to inhibit cell proliferation and regulate pubertal mammary gland development in mice. In the present study, we examined whether and how Zfhx3 regulates lactogenic differentiation in mouse mammary glands. At different stages of mammary gland development, Zfhx3 protein was expressed at varying levels, with the highest level at lactation. In the HC11 mouse mammary epithelial cell line, an in vitro model of lactogenesis, knockdown of Zfhx3 attenuated prolactin-induced β-casein expression and morphological changes, indicators of lactogenic differentiation. In mouse mammary tissue, knock-out of Zfhx3 interrupted lactogenesis, resulting in underdeveloped glands with much smaller and fewer alveoli, reduced β-casein expression, accumulation of large cytoplasmic lipid droplets in luminal cells after parturition, and failure in lactation. Mechanistically, Zfhx3 maintained the expression of Prlr (prolactin receptor) and Prlr-Jak2-Stat5 signaling activity, whereas knockdown and knock-out of Zfhx3 in HC11 cells and mammary tissues, respectively, decreased Prlr expression, Stat5 phosphorylation, and the expression of Prlr-Jak2-Stat5 target genes. These findings indicate that Zfhx3 plays an essential role in proper lactogenic development in mammary glands, at least in part by maintaining Prlr expression and Prlr-Jak2-Stat5 signaling activity.