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• Cellular lineage commitment within hematopoiesis is reviewed. • Insights from novel lineage tracing and single-cell transcriptomics studies are discussed. • How single cell proteomics has resolved cell state transitions in hematopoiesis is described. Blood production is essential to maintain human health, and even small perturbations in hematopoiesis can cause disease. Hematopoiesis has therefore been the focus of much research for many years. Experiments determining the lineage potentials of hematopoietic stem and progenitor cells (HSPCs) in vitro and after transplantation revealed a hierarchy of progenitor cell states, where differentiating cells undergo lineage commitment—a series of irreversible changes that progressively restrict their potential. New technologies have recently been developed that allow for a more detailed analysis of the molecular states and fates of differentiating HSPCs. Proteomic and lineage-tracing approaches, alongside single-cell transcriptomic analyses, have recently helped to reveal the biological complexity underlying lineage commitment during hematopoiesis. Recent insights from these new technologies were presented by Dr. Marjorie Brand and Dr. Allon Klein in the Summer 2019 ISEH Webinar, and are discussed in this Perspective. [ABSTRACT FROM AUTHOR]

• Sox2 knockout in HCs increased the number of Type I HCs and decreased the number of Type II HCs. • The effect of Sox2 -knockout persisted into adulthood, resulting in an increased number of Type I HCs. • The results demonstrated that SOX2 plays a critical role in Type I and Type II HC fate determination. The vestibular system of the inner ear contains Type I and Type II hair cells (HCs) generated from sensory progenitor cells; however, little is known about how the HC subtypes are formed. Sox2 (encoding SRY-box 2) is expressed in Type II, but not in Type I, HCs. The present study aimed to investigate the role of SOX2 in cell fate determination in Type I vs. Type II HCs. First, we confirmed that Type I HCs developed from Sox2- expressing cells through lineage tracing of Sox2- positive cells using a CAG-tdTomato reporter mouse crossed with a Sox2-CreER mouse. Then, Sox2 loss of function was induced in HCs, using Sox2 flox transgenic mice crossed with a Gfi1-Cre driver mouse. Knockout of Sox2 in HCs increased the number of Type I HCs and decreased the number of Type II HCs, while the total number of HCs and Sox2- positive supporting cells did not change. In addition, the effect of Sox2 -knockout persisted into adulthood, resulting in an increased number of Type I HCs. These results demonstrate that SOX2 plays a critical role in the determination of Type II vs. Type I HC fate. The results suggested that Sox2 is a potential target for generating Type I HCs, which may be important for regenerative strategies for balance disorders. [ABSTRACT FROM AUTHOR]

Uncovering the mechanisms that underlie central noradrenergic neuron heterogeneity is essential to understanding selective subtype vulnerability to disease and environmental insult. Using recombinase-based intersectional genetic fate mapping we have previously demonstrated that molecularly distinct progenitor populations give rise to mature noradrenergic neurons differing in their anatomical location, axon morphology and efferent projection pattern. Here we review the findings from our previous study and extend our analysis of the noradrenergic subpopulation defined by transient developmental expression of Hoxb1. Using a combination of intersectional genetic fate mapping and analysis of a targeted loss of function mutation in Hoxb1 , we have now uncovered additional heterogeneity based on the requirement of some noradrenergic neurons for Hoxb1 expression. By comparing the distribution of noradrenergic neurons derived from the Hoxb1 expression domain in wild-type and mutant mice, we demonstrate that Hoxb1 expression is required by a subset of neurons in the pons. Additional fate mapping, using a Hoxb1 enhancer element that drives Cre recombinase expression exclusively in rhombomere 4 of the hindbrain, reveals the existence of a subpopulation of noradrenergic neurons in the pons with more restricted axonal targets than the full Hoxb1 -derived subpopulation. The unique projection profile of this newly defined subpopulation suggests that it may be functionally distinct. These analyses shed new light on the molecular determinants of noradrenergic identity in the pons and the overall complexity of the central noradrenergic system. This article is part of a Special Issue entitled SI: Noradrenergic System . [ABSTRACT FROM AUTHOR]

The article discusses the research on how the Cre-loxP system can circumvent the problem of label dilution through induction of reporter genes and how it can be used to visualize cell lineages. It states that it allows to follow cell fate decision of stem/progenitor cell populations. It mentions that the expression of reporter genes and Cre-inducing agents have direct effect on the behavior of cell due to lack of suitable controls.

Differentiation of hematopoietic stem cells into distinct cell types was thought to occur through a series of discrete, stable progenitor states. Work from Velten et al. (2017) now shows that hematopoietic cells differentiate via a mechanism of continuous lineage priming and thus represent a CLOUD-HSPC. [ABSTRACT FROM AUTHOR]

Abstract: The origins of liver progenitor cells have been extensively studied, but evidence on the origin of pancreatic precursor cells is currently limited. Pancreatic and duodenal homeobox gene 1 (Pdx1) is one of the earliest known markers for the pancreas. A transgenic mouse line expressing green fluorescent protein (GFP) under the control of the Pdx1 promoter showed that Pdx1/GFP expression was first observed in the mid-region of the anterior intestinal portal (AIP) lip at embryonic day (E) 8.5 at the 5–6 somite stage (ss). The liver progenitors were confirmed to originate from separate domains at the lateral endoderm and the inner part of the medial AIP as previously reported (), which turned out to lie caudally to the Pdx1/GFP-expressing domain. To confirm if the early Pdx1/GFP-positive cells give rise to the pancreatic bud, we labeled the cells on the lip of the AIP using the carbocyanine dye CM-DiI and traced their fates in 1–4 ss, 5–6 ss and 7–9 ss E8.5 embryos using an ex utero whole embryo culture method. At 1 ss, the ventral pancreas progenitors were observed in the lateral endoderm, not yet being segregated from the liver or gut progenitors. Cells that contributed solely to the ventral pancreas first appeared at the AIP lip from 5 ss. At 5–6 ss, cells from the medial of the AIP lip contributed to the ventral pancreas. The pancreas fate region become narrower as development progresses. At 7–9 ss, the cells contributing to the ventral pancreas resided in a narrow region of the AIP lip. From 5 ss, the right flanking region contributes to the posterior gut, and the left flanking region contributes to the anterior gut. Dorsal pancreatic progenitors originate from the dorsal endoderm at the 3–6 somite level at 7–9 ss, though they have not yet diverged from the dorsal gut progenitors at this stage. [Copyright &y& Elsevier]

Microglia/macrophage mediated-inflammation, a main contributor to the microenvironment after spinal cord injury (SCI), persists for a long period of time and affects SCI repair. However, the effects of microglia/macrophage mediated-inflammation on neurogenic differentiation of endogenous neural stem/progenitor cells (NSPCs) are not well understood. In this study, to attenuate activated microglia/macrophage mediated-inflammation in the spinal cord of complete transection SCI mice, a combination of photo-crosslinked hydrogel transplantation and CSF1R inhibitor (PLX3397) treatment was used to replace the prolonged, activated microglia/macrophages via cell depletion and repopulation. This combined treatment in SCI mice produced a significant reduction in CD68-positive reactive microglia/macrophages and mRNA levels of pro-inflammatory factors, and a substantial increase in the number of Tuj1-positive neurons in the lesion area compared with single treatment methods. Moreover, most of the newborn Tuj1-positive neurons were confirmed to be generated from endogenous NSPCs using a genetic fate mapping mouse line (Nestin-CreERT2; LSL-tdTomato) that can label and trace NSPC marker-nestin expressing cells and their progenies. Collectively, our findings show that the combined treatment method for inhibiting microglia/macrophage mediated-inflammation promotes endogenous NSPC neurogenesis and improves functional recovery, which provides a promising therapeutic strategy for complete transection SCI. [ABSTRACT FROM AUTHOR]

The presence or relative proportion of progesterone nuclear receptors (PR) in different tissues may contribute to sexual dimorphism in these tissues. PR is expressed in chondrocytes, but its function is mostly unknown. We hypothesized that the PR may regulate chondrocyte metabolism and affect subchondral bone structure. We utilized genetic fate mapping and immunohistochemistry to elucidate PR expression in and effect on cartilage. To define sex-dependent and chondrocyte-specific effects of the PR on subchondral bone, we selectively deleted PR in osteochondrogenic progenitor cells marked by Prx1 (Prx1; PRcKO) and Collagen 2 (Col2; PRcKO), or in matured chondrocytes marked by aggrecan (Acan; PRcKO) and evaluated subchondral bone structure at 4 months of age. Chondrocyte aging was monitored by anti-senescence marker p16INK4a, and MMP13, one of the Senescence-Associated Secretary Phenotype (SASP) components. Compared to wild-type (WT) mice, the female Prx1; PRcKO and the Col2; PRcKO mice had greater total subchondral bone volume and greater subchondral cortical bone thickness, with increased estimated subchondral bone stiffness and failure load in both female and male Col2; PRcKO mice. Moreover, Col2; PRcKO mice from both sexes had greater bone formation and bone strength at the femurs. In contrast, we did not observe any subchondral bone changes in Acan; PRcKO mice other than higher work-to-failure observed in the male Acan; PRcKO mice. Despite no detected difference in articular cartilage between the WT and the PR; chondrocyte conditional deletion mice, there were greater numbers of senescent chondrocytes and increased MMP13 expression, especially in the male mutant mice. These findings suggest that selective inhibition of PR in osteoprogenitor cells, but not in terminally differentiated chondrocytes, induced an increased subchondral bone phenotype and high estimated subchondral bone strength, which might be associated with the development of osteoarthritis in older age. • Selectively deleted progesterone receptor (PR) from osteoprogenitor cells or in the chondrocytes in both sexes. • Focused on subchondral bone structures, which may be related to osteoarthritis incidence and progression. • We found that selective inhibition of PR in osteoprogenitor cells, but not in terminally differentiated chondrocytes, increased subchondral bone mass with sex differences. [ABSTRACT FROM AUTHOR]

Adult hippocampal neurogenesis plays the pivotal roles in central nervous system diseases. Recently, it has been reported that levetiracetam (LEV), a new antiepileptic drug with novel chemical construction and unique pharmacological properties, suppressed aberrant adult subventricular zone (SGZ) neurogenesis in kainite-induced epileptic mice, while promoted adult SGZ neuroblast differentiation in normal mice. These studies indicate LEV can modulate adult hippocampal neurogenesis, but the exact mechanism remained unknown. Thus, the present study aimed to investigate the effects of subchronic and chronic LEV treatments on neural stem cell by lineage tracing in adult hippocampal dentate gyrus of mice, as well as the potential mechanism related to Wnt/β-catenin signaling pathway. The data showed that both subchronic and chronic LEV treatments had no effects on body weight, locomotor activity and anxiety-like behavior in mice. Notably, subchronic LEV treatment significantly suppressed the proliferation of intermediate progenitor cell and neuroblast, decreased the number of intermediate progenitor cell and neuroblast, but increased the number of quiescent neural stem cell. On the contrary, chronic LEV treatment promoted the proliferation of neural stem cell, intermediate progenitor cell and neuroblast, increased the number of neural stem cell, intermediate progenitor cell and neuroblast, and promoted differentiation of newborn immature neuron and mature neuron. Furthermore, subchronic LEV treatment decreased the level of Wnt 3a and nuclear β-Catenin expression, which led to the inhibition on Wnt/β-catenin signaling pathway. Chronic LEV treatment increased the level of Wnt 3a, cytosolic β-catenin and nuclear β-Catenin, decreased the expression of GSK-3β, p-Tyr216-GSK-3β and Axin2, resulting in the enhancement of Wnt/β-catenin signaling pathway. These results demonstrated that LEV significantly suppressed or promoted adult hippocampal neurogenesis in mice by subchronic or chronic treatment possibly through the regulation of Wnt/β-catenin signaling pathway. Our findings provided the new perspectives of LEV on adult hippocampal neurogenesis underlying its clinical application. • Subchronic and chronic LEV had no effects on body weight, locomotor activity and anxiety-like behavior in mice. • Subchronic LEV suppressed adult hippocampal neurogenesis, but chronic LEV promoted adult hippocampal neurogenesis. • Subchronic LEV inhibited on Wnt/β-catenin signaling, but chronic LEV enhanced of Wnt/β-catenin signaling pathway.. [ABSTRACT FROM AUTHOR]