Probes for INS

Temporal transcription profiles of fetal testes with Sertoli cell ablation were examined in 4-day culture using a diphtheria toxin (DT)-dependent cell knockout system in AMH-TRECK transgenic (Tg) mice. RNA analysis revealed that ovarian-specific genes, including Foxl2, were ectopically expressed in DT-treated Tg testis explants initiated at embryonic days 12.5-13.5. FOXL2-positive cells were ectopically observed in two testicular regions-near the testicular surface epithelia and around its adjacent mesonephros. The surface FOXL2-positive cells, together with ectopic expression of Lgr5 and Gng13 (markers of ovarian cords), were derived from the testis epithelia/subepithelia, whereas another FOXL2-positive population was the 3βHSD-negative stroma near the mesonephros. In addition to high expression of Fgfr1/Fgfr2 and heparan sulfate proteoglycan (a reservoir for FGF ligand) in these two sites, exogenous FGF9 additives repressed DT-dependent Foxl2 upregulation in Tg testes. These findings imply retention of Foxl2 inducibility in the surface epithelia and peri-mesonephric stroma of the testicular parenchyma, in which certain paracrine signals, including FGF9 derived from fetal Sertoli cells, repress feminization in these two sites of the early fetal testis.

In mammalian ovaries, immature oocytes are reserved in primordial follicles until their activation for potential ovulation. Precise control of primordial follicle activation (PFA) is essential for reproduction, but how this is achieved is unclear. Here, we show that canonical wingless-type MMTV integration site family (WNT) signaling is pivotal for pre-granulosa cell (pre-GC) activation during PFA. We identified several WNT ligands expressed in pre-GCs that act in an autocrine manner. Inhibition of WNT secretion from pre-GCs/GCs by conditional knockout (cKO) of the wntless (Wls) gene led to female infertility. In Wls cKO mice, GC layer thickness was greatly reduced in growing follicles, which resulted in impaired oocyte growth with both an abnormal, sustained nuclear localization of forkhead box O3 (FOXO3) and reduced phosphorylation of ribosomal protein S6 (RPS6). Constitutive stabilization of β-catenin (CTNNB1) in pre-GCs/GCs induced morphological changes of pre-GCs from a squamous into a cuboidal form, though it did not influence oocyte activation. Our results reveal that canonical WNT signaling plays a permissive role in the transition of pre-GCs to GCs, which is an essential step to support oocyte growth.

Fibroblast growth factor (FGF) signaling plays several important roles in the development of the central nervous system. During the mid-gestation stage, FGF receptors (FGFRs) are expressed in the ventricular zone of the telencephalon and regulate the proliferation and neuronal differentiation of radial glial cells (RGCs). Inhibition of FGFR signaling at this stage results in abnormal brain formation, particularly loss of FGFR1 signaling causes hypoplasia of the olfactory bulb (OB). However, how FGFR1 signaling regulates OB formation is not fully understood. In this study, we inhibited FGFR1 signaling specifically in the anterior telencephalon, where OBs develop, and examined its effects on the development of RGCs in the OB (OB RGCs) and OB formation. The results suggest that inhibition of FGFR1 signaling causes a shift in the state of OB RGCs from proliferation to neuronal differentiation, resulting in an insufficient number of OB projection neurons. Furthermore, activation of Notch signaling, which maintains the self-renewal state of OB RGCs, partially rescued the early abnormal OB formation caused by inhibition of FGFR1 signaling. In contrast, inhibition of FGFR1 signaling in lateral ganglionic eminence did not affect the production of OB interneurons or OB formation. Moreover, the early abnormal OB formation induced by inhibition of FGFR1 signaling could be rescued by overactivation of Notch signaling, which maintains the proliferative state of radial glial cells. These results suggest that FGFR1 signaling regulates normal OB formation by controlling OB RGCs to produce a normal number of OB projection neurons.

Pancreatic development requires spatially and temporally controlled expression of growth factors derived from mesenchyme. Here, we report that in mice the secreted factor Fgf9 is expressed principally by mesenchyme and then mesothelium during early development, then subsequently by both mesothelium and rare epithelial cells by E12.5 and onwards. Global knockout of the Fgf9 gene resulted in the reduction of pancreas and stomach size, as well as complete asplenia. The number of early Pdx1+ pancreatic progenitors was reduced at E10.5, as was proliferation of mesenchyme at E11.5. Although loss of Fgf9 did not interfere with differentiation of later epithelial lineages, single-cell RNA-Sequencing identified transcriptional programs perturbed upon loss of Fgf9 during pancreatic development, including loss of the transcription factor Barx1. Lastly, we identified conserved expression patterns of FGF9 and receptors in human fetal pancreas, suggesting that FGF9 expressed by pancreatic mesenchyme may similarly affect the development of the human pancreas.