Probes for INS

Bicuspid aortic valve (BAV), the most common cardiovascular malformation occurs in 0.5-1.2% of the population. Although highly heritable, few causal mutations have been identified in BAV patients. Here, we report the targeted sequencing of HOXA1 in a cohort of BAV patients and the identification of rare indel variants in the homopolymeric histidine tract of HOXA1. In vitro analysis shows that disruption of this motif leads to a significant reduction in protein half-life and defective transcriptional activity of HOXA1. In zebrafish, targeting hoxa1a ortholog results in aortic valve defects. In vivo assays indicates that these variants behave as dominant negatives leading abnormal valve development. In mice, deletion of Hoxa1 leads to BAV with a very small, rudimentary non-coronary leaflet. We also show that 17% of homozygous Hoxa1-1His knock-in mice present similar phenotype. Genetic lineage tracing in Hoxa1-/- mutant mice reveals an abnormal reduction of neural crest-derived cells in the valve leaflet, which is caused by a failure of early migration of these cells.

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.

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.

Oligodendrogenesis in the human central nervous system has been observed mainly at the second trimester of gestation, a much later developmental stage compared to oligodendrogenesis in mice. Here, we characterize the transcriptomic neural diversity in the human forebrain at post-conception weeks (PCW) 8-10. Using single-cell RNA sequencing, we find evidence of the emergence of a first wave of oligodendrocyte lineage cells as early as PCW 8, which we also confirm at the epigenomic level through the use of single-cell ATAC-seq. Using regulatory network inference, we predict key transcriptional events leading to the specification of oligodendrocyte precursor cells (OPCs). Moreover, by profiling the spatial expression of 50 key genes through the use of in situ sequencing (ISS), we identify regions in the human ventral fetal forebrain where oligodendrogenesis first occurs. Our results indicate evolutionary conservation of the first wave of oligodendrogenesis between mice and humans and describe regulatory mechanisms involved in human OPC specification.

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.