Molecular Actions Underlying Wolffian Duct Regression in Sexual Differentiation of Murine Reproductive Tracts

The NR2F2-HAND2 signaling axis regulates progesterone actions in the uterus at early pregnancy

Endometrial function is dependent on a tight crosstalk between the epithelial and stromal cells of the endometrium. This communication is critical to ensure a fertile uterus and relies on progesterone and estrogen signaling to prepare a receptive uterus for embryo implantation in early pregnancy. One of the key mediators of this crosstalk is the orphan nuclear receptor NR2F2, which regulates uterine epithelial receptivity and stromal cell differentiation. In order to determine the molecular mechanism regulated by NR2F2, RNAseq analysis was conducted on the uterus of PgrCre;Nr2f2f/f mice at Day 3.5 of pregnancy. This transcriptomic analysis demonstrated Nr2f2 ablation in Pgr-expressing cells leads to a reduction of Hand2 expression, increased levels of Hand2 downstream effectors Fgf1 and Fgf18, and a transcriptome manifesting suppressed progesterone signaling with an altered immune baseline. ChIPseq analysis conducted on the Day 3.5 pregnant mouse uterus for NR2F2 demonstrated the majority of NR2F2 occupies genomic regions that have H3K27ac and H3K4me1 histone modifications, including the loci of major uterine transcription regulators Hand2, Egr1, and Zbtb16. Furthermore, functional analysis of an NR2F2 occupying site that is conserved between human and mouse was capable to enhance endogenous HAND2 mRNA expression with the CRISPR activator in human endometrial stroma cells. These data establish the NR2F2 dependent regulation of Hand2 in the stroma and identify a cis-acting element for this action. In summary, our findings reveal a role of the NR2F2-HAND2 regulatory axis that determines the uterine transcriptomic pattern in preparation for the endometrial receptivity.

Epithelial and mesenchymal fate decisions in Wolffian duct development

Wolffian ducts (WDs) are the paired embryonic structures that give rise to internal male reproductive tract organs. WDs are initially formed in both sexes but have sex-specific fates during sexual differentiation. Understanding WD differentiation requires insights into the process of fate decisions of epithelial and mesenchymal cells, which are tightly coordinated by endocrine, paracrine, and autocrine signals. In this review, we discuss current advances in understanding the fate-decision process of WD epithelial and mesenchymal lineages from their initial formation at the embryonic stage to postnatal differentiation. Finally, we discuss aberrant cell differentiation in WD abnormalities and pathologies and identify opportunities for future investigations.

Integration of mouse ovary morphogenesis with developmental dynamics of the oviduct, ovarian ligaments, and rete ovarii

Morphogenetic events during the development of the fetal ovary are crucial to the establishment of female fertility. However, the effects of structural rearrangements of the ovary and surrounding reproductive tissues on ovary morphogenesis remain largely uncharacterized. Using tissue clearing and lightsheet microscopy, we found that ovary folding correlated with regionalization into cortex and medulla. Relocation of the oviduct to the ventral aspect of the ovary led to ovary encapsulation, and mutual attachment of the ovary and oviduct to the cranial suspensory ligament likely triggered ovary folding. During this process, the rete ovarii (RO) elaborated into a convoluted tubular structure extending from the ovary into the ovarian capsule. Using genetic mouse models in which the oviduct and RO are perturbed, we found the oviduct is required for ovary encapsulation. This study reveals novel relationships among the ovary and surrounding tissues and paves the way for functional investigation of the relationship between architecture and differentiation of the mammalian ovary.

One Tool for Many Jobs: Divergent and Conserved Actions of Androgen Signaling in Male Internal Reproductive Tract and External Genitalia

In the 1940s, Alfred Jost demonstrated the necessity of testicular secretions, particularly androgens, for male internal and external genitalia differentiation. Since then, our knowledge of androgen impacts on differentiation of the male internal (Wolffian duct) and external genitalia (penis) has been drastically expanded upon. Between these two morphologically and functionally distinct organs, divergent signals facilitate the establishment of tissue-specific identities. Conversely, conserved actions of androgen signaling are present in both tissues and are largely responsible for the growth and expansion of the organs. In this review we synthesize the existing knowledge of the cell type-specific, organ specific, and conserved signaling mechanisms of androgens. Mechanistic studies on androgen signaling in the Wolffian duct and male external genitalia have largely been conducted in mouse model organisms. Therefore, the majority of the review is focused on mouse model studies.