Development
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In the adult rodent brain, neural stem cells (NSCs) persist in the ventricular-subventricular zone (V-SVZ) and the subgranular zone (SGZ), which are specialized niches in which young neurons for the olfactory bulb (OB) and hippocampus, respectively, are generated. Recent studies have significantly modified earlier views on the mechanisms of NSC self-renewal and neurogenesis in the adult brain. ⋯ We also review recent advances in single cell RNA analyses that reveal the complexity of adult neurogenesis. These findings set the stage for a better understanding of adult neurogenesis, a process that one day may inspire new approaches to brain repair.
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In vivo genetic mutation has become a powerful tool for dissecting gene function; however, multi-gene interaction and the compensatory mechanisms involved can make findings from single mutations, at best difficult to interpret, and, at worst, misleading. Hence, it is necessary to establish an efficient way to disrupt multiple genes simultaneously. CRISPR/Cas9-mediated base editing disrupts gene function by converting a protein-coding sequence into a stop codon; this is referred to as CRISPR-stop. ⋯ Finally, we successfully disrupted vGlut3, Otof and prestin simultaneously. Our results show that CRISPR-stop can efficiently generate single or triple homozygous F0 mouse mutants, bypassing laborious mouse breeding. We believe that CRISPR-stop is a powerful method that will pave the way for high-throughput screening of mouse developmental and functional genes, matching the efficiency of methods available for model organisms such as Drosophila.
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The bone morphogenetic protein (BMP) signaling pathway, including antagonists, functions in lung development and regeneration of tracheal epithelium from basal stem cells. Here, we explore its role in the alveolar region, where type 2 epithelial cells (AT2s) and Pdgfrα+ type 2-associated stromal cells (TASCs) are components of the stem cell niche. We use organoids and in vivo alveolar regrowth after pneumonectomy (PNX) - a process that requires proliferation of AT2s and differentiation into type 1 cells (AT1s). ⋯ Gain- and loss-of-function genetic manipulation reveals that reduced BMP signaling in AT2s after PNX allows self-renewal but reduces differentiation; conversely, increased BMP signaling promotes AT1 formation. Constitutive BMP signaling in Pdgfrα+ cells reduces their AT2 support function, both after PNX and in organoid culture. Our data reveal multiple cell-type-specific roles for BMP signaling during alveolar regeneration.
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The molecular mechanism by which NSC number is controlled in the neurogenic regions of the adult brain is not fully understood but it has been shown that vascular niche signals regulate neural stem cell (NSC) quiescence and growth. Here, we have uncovered a role for soluble amyloid precursor protein (sAPP) as a vascular niche signal in the subventricular zone (SVZ) of the lateral ventricle of the adult mouse brain. sAPP suppresses NSC growth in culture. Further in vivo studies on the role of APP in regulating NSC number in the SVZ clearly demonstrate that endothelial deletion of App causes a significant increase in the number of BrdU label-retaining NSCs in the SVZ, whereas NSC/astrocyte deletion of App has no detectable effect on the NSC number. Taken together, these results suggest that endothelial APP functions as a vascular niche signal that negatively regulates NSC growth to control the NSC number in the SVZ.
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Adult stem cells from a variety of organs can be expanded long-term in vitro as three-dimensional organotypic structures termed organoids. These adult stem cell-derived organoids retain their organ identity and remain genetically stable over long periods of time. The ability to grow organoids from patient-derived healthy and diseased tissue allows for the study of organ development, tissue homeostasis and disease. In this Review, we discuss the generation of adult stem cell-derived organoid cultures and their applications in in vitro disease modeling, personalized cancer therapy and regenerative medicine.