RESUMEN
During the early development of tetrapods, including humans, the embryonic body elongates caudally once the anterior-posterior axis is established. During this process, region-specific vertebral morphogenesis occurs, with the determination of limb positioning along the anterior-posterior axis. We previously reported that Gdf11 functions as an anatomical integration system that determines the positioning of hindlimbs and sacral vertebrae where Gdf11 is expressed. However, the molecular mechanisms underlying induction of Gdf11 expression remain unclear. In this study, we searched for non-coding regions near the Gdf11 locus that were conserved across species to elucidate the regulatory mechanisms of Gdf11 expression. We identified an enhancer of the Gdf11 gene in intron 1 and named it highly conserved region (HCR). In HCR knockout mice, the expression level of endogenous Gdf11 was decreased, and the position of the sacral-hindlimb unit was shifted posteriorly. We also searched for factors upstream of Gdf11 based on the predicted transcription factor binding sites within the HCR. We found that inhibition of FGF signaling increased endogenous Gdf11 expression, suggesting that FGF signaling negatively regulates Gdf11 expression. However, FGF signaling does not regulate HCR activity. Our results suggest that there are species-specific Gdf11 enhancers other than HCR and that FGF signaling regulates Gdf11 expression independent of HCR.
RESUMEN
Cancer stem cells (CSCs), which are critical targets for cancer therapy as they are involved in drug resistance to anticancer drugs, and metastasis, are maintained by angiocrine factors produced by particular niches that form within tumor tissue. Secreted frizzled-related protein 1 (Sfrp1) is an extracellular protein that modulates Wnt signaling. However, the cells that produce Sfrp1 in the tumor environment and its function remain unclear. We aimed to elucidate angiocrine factors related to CSC maintenance, focusing on Sfrp1. Although Sfrp1 is a Wnt pathway-related factor, its impact on tumor tissues remains unknown. We investigated the localization of Sfrp1 in tumors and found that it is expressed in some tumor vessels. Analysis of mice lacking Sfrp1 showed that tumor growth was suppressed in Sfrp1-deficient tumor tissues. Flow cytometry analysis indicated that CSCs were maintained in the early tumor growth phase in the Sfrp1 knockout (KO) mouse model of tumor-bearing cancer. However, tumor growth was inhibited in the late tumor growth phase because of the inability to maintain CSCs. Real-time PCR results from tumors of Sfrp1 KO mice showed that the expression of Wnt signaling target genes significantly decreased in the late stage of tumor growth. This suggests that Sfrp1, an angiocrine factor produced by the tumor vascular niche, is involved in Wnt signaling-mediated mechanisms in tumor tissues.
RESUMEN
Neuromesodermal progenitors (NMPs), serving as the common origin of neural and paraxial mesodermal development in a large part of the trunk, have recently gained significant attention because of their critical importance in the understanding of embryonic organogenesis and the design of in vitro models of organogenesis. However, the nature of NMPs at many essential points remains only vaguely understood or even incorrectly assumed. Here, we discuss the nature of NMPs, focusing on their dynamic migratory behavior during embryogenesis and the mechanisms underlying their neural vs. mesodermal fate choice. The discussion points include the following: (1) How the sinus rhomboidals is organized; the tissue where the neural or mesodermal fate choice of NMPs occurs. (2) NMPs originating from the broad posterior epiblast are associated with Sox2 N1 enhancer activity. (3) Tbx6-dependent Sox2 repression occurs during NMP-derived paraxial mesoderm development. (4) The nephric mesenchyme, a component of the intermediate mesoderm, was newly identified as an NMP derivative. (5) The transition of embryonic tissue development from tissue-specific progenitors in the anterior part to that from NMPs occurs at the forelimb bud axial level. (6) The coexpression of Sox2 and Bra in NMPs is conditional and is not a hallmark of NMPs. (7) The ability of the NMP pool to sustain axial embryo growth depends on Wnt3a signaling in the NMP population. Current in vitro models of NMPs are also critically reviewed.