Transcriptome analysis of the mouse fetal and adult rete ovarii and surrounding tissues

Abstract

The rete ovarii (RO) is an epithelial structure that arises during fetal development in close proximity to the ovary and persists throughout adulthood in mice. However, the functional significance of the RO remains elusive, and it has been absent from recent discussions of female reproductive anatomy. The RO comprises three distinct regions: the intraovarian rete (IOR) within the ovary, the extraovarian rete (EOR) in the periovarian tissue, and the connecting rete (CR) linking the EOR and IOR. We hypothesize that the RO plays a pivotal role in maintaining ovarian homeostasis and responding to physiological changes. To uncover the nature and function of RO cells, we conducted transcriptome analysis, encompassing bulk, single-cell, and nucleus-level sequencing of both fetal and adult RO tissues using thePax8-rtTA; Tre- H2B-GFPmouse line, where all RO regions express nuclear GFP. This study presents three datasets, which highlight RO-specific gene expression signatures and reveal differences in gene expression across the three RO regions during development and in adulthood. The integration and rigorous validation of these datasets will advance our understanding of the RO’s roles in ovarian development, female maturation, and adult female fertility.Short narrativeThis study employs comprehensive bulk, single cell and single nucleus transcriptome analysis to uncover gene expression signatures of the fetal and adult rete ovarii (RO).

Rediscovering theRete Ovarii: a secreting auxiliary structure to the ovary

“…A protein that was prominent on the proteomic candidate list was IGFBP2. We found that Igfbp2 was highly expressed in both the embryonic and adult RO transcriptome (Anbarci et al, 2023). IGFBP2 is an ideal candidate protein to mediate ovarian function.…”

“…In contrast, the ovary and surrounding tissue are more highly innervated than the testis (McKey et al, 2019). A surprising finding in our bulk transcriptome analysis of the RO was the presence of a high proportion of immune cells and cells with vascular markers that co-isolated with E16.5 RO cells (Anbarci et al, 2023).…”

“…1 bottom row). To identify additional RO markers, we performed bulk and single cell RNA sequencing (ScRNA-seq) of cells from the ovarian complex of mice at E16.5 and 2 months, and found that Krt8 was enriched in the RO (Anbarci et al, 2023). We validated these findings using IF against KRT8, which revealed that KRT8+ cells were specifically localized to the EOR (Fig.…”

“…Using IF and confocal imaging, we found that these three regions are maintained throughout development, but their relative sizes change. While the entirety of the RO is PAX8+, we took different approaches to identify region additional RO markers, we performed bulk and single cell RNA sequencing (ScRNA-seq) of cells from the ovarian complex of mice at E16.5 and 2 months and found that Krt8 was enriched in the RO (Anbarci et al, 2023). We validated these findings using IF against KRT8, which revealed that KRT8+ cells were specifically localized to the EOR (Fig.…”

“…To eliminate intracellular proteins arising from lysed cells, we cross-referenced our proteomic dataset with that of the mammalian secretome (Meinken et al, 2015), thereby retaining only known secreted proteins. Next, we compared the resulting list to the E16.5 ScRNA-seq data from cells mapping to the RO (Anbarci et al, 2023). This produced a conservative candidate list of 15 proteins (Table 1).…”