A standardized nomenclature for the mouse and rat prolactin superfamilies

Plasma prolactin axis shift from placental to pituitary origin in late prepartum mice

The placenta secretes a prolactin (PRL)-like hormone PRL3B1 (placental lactogen II), a luteotropic hormone essential for maintaining pregnancy until labor in mice. A report from 1984 examined the secretion pattern of PRL3B1 in prepartum mice. In the current study, we found contradictory findings in the secretion pattern that invalidate the previous report. By measuring maternal plasma PRL3B1 and PRL every 4 hrs from gestational day 17 (G17), we newly discovered that maternal plasma PRL3B1 levels decrease rapidly in prepartum C57BL/6 mice. Interestingly, the onset of this decline coincided with the PRL surge at G18, demonstrating a plasma prolactin axis shift from placental to pituitary origin. We also found that maternal plasma progesterone regression precedes the onset of the PRL shift. The level of Prl3b1 mRNA was determined by RT-qPCR in the placenta and remained stable until parturition, implying that PRL3B1 peptide production or secretion was suppressed. We hypothesized that production of the PRL family, the 25 paralogous PRL proteins exclusively expressed in mice placenta, would decrease alongside PRL3B1 during this period. To investigate this hypothesis and to seek proteomic changes, we performed a shotgun proteome analysis of the placental tissue using data-independent acquisition mass spectrometry (DIA-MS). Up to 5,891 proteins were identified, including 17 PRL family members. Relative quantitative analysis between embryonic day 17 (E17) and E18 placentas showed no significant difference in the expression of PRL3B1 and most PRL family members except PRL7C1. These results suggest that PRL3B1 secretion from the placenta is suppressed at G18 (E18).

A diversity outbred F1 mouse model identifies host-intrinsic genetic regulators of response to immune checkpoint inhibitors

Immune checkpoint inhibitors (ICI) have improved outcomes for a variety of malignancies; however, many patients fail to benefit. While tumor-intrinsic mechanisms are likely involved in therapy resistance, it is unclear to what extent host genetic background influences response. To investigate this, we utilized the Diversity Outbred (DO) and Collaborative Cross (CC) mouse models. DO mice are an outbred stock generated by crossbreeding eight inbred founder strains, and CC mice are recombinant inbred mice generated from the same eight founders. We generated 207 DOB6F1 mice representing 48 DO dams and demonstrated that these mice reliably accept the C57BL/6-syngeneic B16F0 tumor and that host genetic background influences response to ICI. Genetic linkage analysis from 142 mice identified multiple regions including one within chromosome 13 that associated with therapeutic response. We utilized 6 CC strains bearing the positive (NZO) or negative (C57BL/6) driver genotype in this locus. We found that 2/3 of predicted responder CCB6F1 crosses show reproducible ICI response. The chromosome 13 locus contains the murine prolactin family, which is a known immunomodulating cytokine associated with various autoimmune disorders. To directly test whether prolactin influences ICI response rates, we implanted inbred C57BL/6 mice with subcutaneous slow-release prolactin pellets to induce mild hyperprolactinemia. Prolactin augmented ICI response against B16F0, with increased CD8 infiltration and 5/8 mice exhibiting slowed tumor growth relative to controls. This study highlights the role of host genetics in ICI response and supports the use of F1 crosses in the DO and CC mouse populations as powerful cancer immunotherapy models.

The Influence of the Prolactins on the Development of the Uterus in Neonatal Mice

The endometrial gland is one of the most important components of the mammalian uterus. However, few studies have been conducted on the regulatory mechanisms of adenogenesis during the development of endometrium. In the present study, we detected the genes expression of 35 different prolactin family members (PRLs) together with the prolactin receptor (PRL-R) in the endometrium of neonatal mice along with the adenogenesis process, to address which prolactin-like genes play a key role during gland development in mice. We found that: (1) The expression of Prl1a1, Prl3d1, Prl5a1, Prl7a1, Prl7a2, Prl7d1, Prl8a6, Prl8a8, and Prl8a9 genes were significantly increased along with the development of uterine glands. Prl7c1 and Prl8a1 were observably up-regulated on Postnatal day 5 (PND5) when the uterine glandular bud invagination begins. Prl3a1, Prl3b1, and Prl7b1 suddenly increased significantly on PND9. But, Prl3c1 and Prl8a2 were markedly down-regulated on PND5 and the expression of Prl6a1 and Prlr were stable extremely. (2) After continuous injection of Progesterone (P4), a well-known method to suppress the endometrial adenogenesis, the expression of Prl1a1, Prl3d1, Prl5a1, Prl7a1, Prl7a2, Prl7d1, Prl8a6, Prl8a8, Prl8a9, and Prlr were suppressed on PND7. And on PND9, Prl1a1, Prl3d1, Prl8a6, Prl8a8, and Prl8a9 were significantly inhibited. (3) Further analysis of the epithelial and stroma showed that these PRLs were mainly expressed in the endometrial stroma of neonatal mice. Our results indicate that multiple PRLs are involved in uterine development and endometrial adenogenesis. Continued progesterone therapy may alter the expression pattern of these PRLs in endometrial stromal cells, thereby altering the interaction and communication between stroma and epithelium, and ultimately leading to complete suppression of endometrial adenogenesis.

A Prolactin Family Paralog Regulates Placental Adaptations to a Physiological Stressor

The prolactin (PRL) family of hormones and cytokines participates in the regulation of optimal reproductive performance in the mouse and rat. Members of the PRL family are expressed in the anterior pituitary, uterus, and/or placenta. In the present study, we investigated the ontogeny of PRL family 7, subfamily b, member 1 (PRL7B1; also called PRL-like protein-N, PLP-N) expression in the developing mouse placenta and established a mouse model for investigating the biological function of PRL7B1. Transcripts for Prl7b1 were first detected on Gestation Day (d) 8.5. From gestation d8.5 through d14.5, Prl7b1 was expressed in trophoblast cells residing at the interface between maternal mesometrial decidua and the developing placenta. On gestation d17.5, the predominant cellular source of Prl7b1 mRNA was migratory trophoblast cells invading into the uterine mesometrial decidua. The Prl7b1 null mutant allele was generated via replacement of the endogenous Prl7b1 coding sequence with beta-galactosidase (LacZ) reporter and neomycin cassettes. The mutant Prl7b1 allele was successfully passed through the germline. Homozygous Prl7b1 mutant mice were viable and fertile. Under standard animal housing conditions, Prl7b1 had undetectable effects on placentation and pregnancy. Hypoxia exposure during pregnancy evoked adaptations in the organization of the wild-type placenta that were not observed in Prl7b1 null placentation sites. In summary, PRL7B1 is viewed as a part of a pathway regulating placental adaptations to physiological stressors.

Third party data gene data set of eutherian growth hormone genes

Among 146 potential coding sequences, the most comprehensive eutherian growth hormone gene data set annotated 100 complete coding sequences. The eutherian comparative genomic analysis protocol first described 5 major gene clusters of eutherian growth hormone genes. The present updated gene classification and nomenclature of eutherian growth hormone genes integrated gene annotations, phylogenetic analysis and protein molecular evolution analysis into new framework of future experiments. The curated third party data gene data set of eutherian growth hormone genes was deposited in European Nucleotide Archive under accession numbers LM644135-LM644234.

Evolution of Placental Function in Mammals: The Molecular Basis of Gas and Nutrient Transfer, Hormone Secretion, and Immune Responses

Placenta has a wide range of functions. Some are supported by novel genes that have evolved following gene duplication events while others require acquisition of gene expression by the trophoblast. Although not expressed in the placenta, high-affinity fetal hemoglobins play a key role in placental gas exchange. They evolved following duplications within the beta-globin gene family with convergent evolution occurring in ruminants and primates. In primates there was also an interesting rearrangement of a cassette of genes in relation to an upstream locus control region. Substrate transfer from mother to fetus is maintained by expression of classic sugar and amino acid transporters at the trophoblast microvillous and basal membranes. In contrast, placental peptide hormones have arisen largely by gene duplication, yielding for example chorionic gonadotropins from the luteinizing hormone gene and placental lactogens from the growth hormone and prolactin genes. There has been a remarkable degree of convergent evolution with placental lactogens emerging separately in the ruminant, rodent, and primate lineages and chorionic gonadotropins evolving separately in equids and higher primates. Finally, coevolution in the primate lineage of killer immunoglobulin-like receptors and human leukocyte antigens can be linked to the deep invasion of the uterus by trophoblast that is a characteristic feature of human placentation.

Bridging sequence diversity and tissue-specific expression by DNA methylation in genes of the mouse prolactin superfamily

Much of the DNA in genomes is organized within gene families and hierarchies of gene superfamilies. DNA methylation is the main epigenetic event involved in gene silencing and genome stability. In the present study, we analyzed the DNA methylation status of the prolactin (PRL) superfamily to obtain insight into its tissue-specific expression and the evolution of its sequence diversity. The PRL superfamily in mice consists of two dozen members, which are expressed in a tissue-specific manner. The genes in this family have CpG-less sequences, and they are located within a 1-Mb region as a gene cluster on chromosome 13. We tentatively grouped the family into several gene clusters, depending on location and gene orientation. We found that all the members had tissue-dependent differentially methylated regions (T-DMRs) around the transcription start site. The T-DMRs are hypermethylated in nonexpressing tissues and hypomethylated in expressing cells, supporting the idea that the expression of the PRL superfamily genes is subject to epigenetic regulation. Interestingly, the DNA methylation patterns of T-DMRs are shared within a cluster, while the patterns are different among the clusters. Finally, we reconstituted the nucleotide sequences of T-DMRs by converting TpG to CpG based on the consideration of a possible conversion of 5-methylcytosine to thymine by spontaneous deamination during the evolutionary process. On the phylogenic tree, the reconstituted sequences were well matched with the DNA methylation pattern of T-DMR and orientation. Our study suggests that DNA methylation is involved in tissue-specific expression and sequence diversity during evolution.

Chromosome-substituted rat strains provide insights into the genetics of placentation

The rat possesses a hemochorial form of placentation. Pronounced intrauterine trophoblast cell invasion and vascular remodeling characterize this type of placentation. Strain-specific patterns of placentation are evident in the rat. Some rat strains exhibit deep intrauterine trophoblast invasion and an expanded junctional zone [Holtzman Sprague-Dawley (HSD), Dahl salt sensitive (DSS)], whereas placentation sites of other rat strains are characterized by shallow invasion and a restricted junctional zone [Brown Norway (BN)]. In this report, we identified a quantitative trait that was used to distinguish strain-specific features of rat placentation. Junctional zone prolactin family 5, subfamily a, member 1 (Prl5a1) transcript levels were significantly greater in BN rats than in HSD or DSS rats. Prl5a1 transcript levels were used as a quantitative trait to screen placentation sites from chromosome-substituted rat strains (BN chromosomes introgressed into the DSS inbred strain; DSS-BN panel). Litter size, placental weights, and fetal weights were not significantly different among the chromosome-substituted strains. Regulation of the junctional zone Prl5a1 transcript-level quantitative trait was multifactoral. Chromosome-substituted strains possessing BN chromosomes 14 or 17 introgressed into the DSS inbred rat strain displayed Prl5a1 transcript levels that were significantly different from the DSS pattern and more closely resembled the BN pattern. The in situ placental distribution of Prl5a1 mRNA and the structure of the junctional zone of DSS-BN17 rats mimicked that observed for the BN rat. Prl5a1 gene expression was also assessed in BN vs. HSD trophoblast stem cells and following reciprocal BN and HSD embryo transfer. Strain differences intrinsic to trophoblast and maternal environment were identified. In summary, we have identified chromosomes 14 and 17 as possessing regulatory information controlling a quantitative trait associated with rat placentation.

PPARgamma in placental angiogenesis

Peroxisome proliferator-activated receptor γ (PPARγ) is a nuclear receptor involved in diverse biological processes including adipocyte differentiation, glucose homeostasis, and inflammatory responses. Analyses of PPARγ knockout animals have been so far preempted by the early embryonic death of PPARγ-/- embryos as a consequence of the severe alteration of their placental vasculature. Using Sox2Cre/PPARγL2/L2 mice, we obtained fully viable PPARγ-null mice through specific and total epiblastic gene deletion, thereby demonstrating that the placental defect is the unique cause of PPARγ-/- embryonic lethality. The vasculature defects observed in PPARγ-/- placentas at embryonic d 9.5 correlated with an unsettled balance of pro- and antiangiogenic factors as demonstrated by increased levels of proliferin (Prl2c2, PLF) and decreased levels of proliferin-related protein (Prl7d1, PRP), respectively. To analyze the role of PPARγ in the later stage of placental development, when its expression peaks, we treated pregnant wild-type mice with the PPARγ agonist rosiglitazone. This treatment resulted in a disorganization of the placental layers and an altered placental microvasculature, accompanied by the decreased expression of proangiogenic genes such as Prl2c2, vascular endothelial growth factor, and Pecam1. Together our data demonstrate that PPARγ plays a pivotal role in controlling placental vascular proliferation and contributes to its termination in late pregnancy.

Alpha3beta1 integrin in epidermis promotes wound angiogenesis and keratinocyte-to-endothelial-cell crosstalk through the induction of MRP3

During cutaneous wound healing, epidermal keratinocytes play essential roles in the secretion of factors that promote angiogenesis. However, specific cues in the wound microenvironment that trigger the production of pro-angiogenic factors by keratinocytes, and the cellular receptors that mediate this response, remain unclear. In this study, we exploited a model of conditional integrin knockout to demonstrate impaired wound angiogenesis in mice that lack alpha3beta1 integrin in epidermis. In addition, we used genetic and shRNA approaches to determine that alpha3beta1-integrin deficiency in keratinocytes leads to reduced mRNA and protein expression of the pro-angiogenic factor mitogen-regulated protein 3 (MRP3; also known as PRL2C4), and to demonstrate that this regulation provides a mechanism of keratinocyte-to-endothelial-cell crosstalk that promotes endothelial-cell migration. Finally, we showed that the impaired wound angiogenesis in epidermis-specific alpha3-integrin-knockout mice is correlated with reduced expression of MRP3 in wounded epidermis. These findings identify a novel role for alpha3beta1 integrin in promoting wound angiogenesis through a mechanism of crosstalk from epidermal to endothelial cells, and they implicate MRP3 in this integrin-dependent crosstalk. Such a mechanism represents a novel paradigm for integrin-mediated regulation of wound angiogenesis that extends beyond traditional roles for integrins in cell adhesion and migration.

Spatial and temporal expression of the 23 murine Prolactin/Placental Lactogen-related genes is not associated with their position in the locus

Background

The Prolactin (PRL) hormone gene family shows considerable variation among placental mammals. Whereas there is a single PRL gene in humans that is expressed by the pituitary, there are an additional 22 genes in mice including the placental lactogens (PL) and Prolactin-related proteins (PLPs) whose expression is limited to the placenta. To understand the regulation and potential functions of these genes, we conducted a detailed temporal and spatial expression study in the placenta between embryonic days 7.5 and E18.5 in three genetic strains.

Results

Of the 22 PRL/PL genes examined, only minor differences were observed among strains of mice. We found that not one family member has the same expression pattern as another when both temporal and spatial data were examined. There was also no correlation in expression between genes that were most closely related or between adjacent genes in the PRL/PL locus. Bioinformatic analysis of upstream regulatory regions identified conserved combinations (modules) of putative transcription factor binding sites shared by genes expressed in the same trophoblast subtype, supporting the notion that local regulatory elements, rather than locus control regions, specify subtype-specific expression. Further diversification in expression was also detected as splice variants for several genes.

Conclusion

In the present study, a detailed temporal and spatial placental expression map was generated for all murine PRL/PL family members from E7.5 to E18.5 of gestation in three genetic strains. This detailed analysis uncovered several new markers for some trophoblast cell types that will be useful for future analysis of placental structure in mutant mice with placental phenotypes. More importantly, several main conclusions about regulation of the locus are apparent. First, no two family members have the same expression pattern when both temporal and spatial data are examined. Second, most genes are expressed in multiple trophoblast cell subtypes though none were detected in the chorion, where trophoblast stem cells reside, or in syncytiotrophoblast of the labyrinth layer. Third, bioinformatic comparisons of upstream regulatory regions identified predicted transcription factor binding site modules that are shared by genes expressed in the same trophoblast subtype. Fourth, further diversification of gene products from the PRL/PL locus occurs through alternative splice isoforms for several genes.