Stem Cell Reports最新文献

Alternative splicing events have emerged as a rapid regulatory layer in gene expression. Lin et al. demonstrate that alternative splicing is widespread during muscle stem cell activation. Its functional importance is illustrated through an RNA-binding fox 1-homolog 2 (RBFOX2)-dependent splice choice in the Notch regulator Numb, showing how inclusion of a single exon can tune Notch signaling to regulate the transition from quiescence to activation.

Satellite cells (SCs) are somatic stem cells essential for skeletal muscle regeneration. Most SCs remain quiescent in resting muscle, but they rapidly activate in response to stimuli. Although post-transcriptional regulation has been implicated in SC functions, the role of alternative splicing (AS) during SC activation remains unclear. Using in vivo fixation to preserve quiescent SCs, we uncovered rapid and extensive AS changes upon activation, affecting genes involved in fundamental pathways. We identified RBFOX2 as a key AS regulator in SCs; its loss delayed both SC activation and muscle regeneration. Particularly, RBFOX2 promotes the inclusion of exon 6 in Numb, a Notch pathway regulator. This exon is required for SC activation, and its skipping delays activation while upregulating Notch signaling. Altogether, our study provides the AS landscape during SC activation and demonstrates that a single-gene splicing change can significantly influence SC activation and essential pathways such as Notch signaling.

Previous studies on hematopoiesis were mainly conducted in model animals. However, direct investigation of human hematopoiesis remains challenging due to limited access to human samples and ethical concerns. Traditional two-dimensional culture systems have provided valuable opportunities to study human hematopoiesis, but they fail to fully recapitulate the behaviors of hematopoietic cells and their interactions with niche cells as observed in vivo. In recent years, organoid technologies have emerged as a powerful approach for modeling hematopoietic development, maintenance, and diseases. By mimicking the key architectural and functional characteristics of native hematopoietic tissues, hematopoietic organoids (HOs) offer promising platforms for studying developmental hematopoiesis, modeling hematological diseases, performing drug screening, and generating functional hematopoietic cells. In this review, we summarize recent progress in HO construction, explore their potential applications in both basic research and clinical translation, and discuss current opportunities and remaining challenges in generating physiologically relevant HO models.

Embryonic stem cells (ESCs) can self-renew and differentiate into somatic cells. They can also adopt a totipotent-like state and become 2-cell-like cells (2CLCs). However, how these progresses are regulated remains poorly understood. Here, we define a novel role for Rbm25 (RNA-binding motif protein 25), previously known as a splicing regulator, in the maintenance of ESC identity. Rbm25 is highly expressed in ESCs and is downregulated during differentiation. Deletion or depletion of Rbm25 impairs ESC self-renewal and differentiation and promotes the transition toward 2CLCs. Mechanistically, RBM25 occupies pluripotency- and DNA methylation-related gene promoters and directly regulates their expression, thereby governing the gene expression program and the epigenetic state of ESCs. Together, our data indicate that Rbm25 controls stem cell fate specification at the transcription level and therefore uncover a new role of Rbm25 as a transcriptional regulator.

Merkel cells (MCs) are specialized mechanoreceptors crucial for tactile sensation, yet their developmental investigation remains challenging, particularly in humans, due to the lack of validated in vitro culture system. Here, we establish novel approaches, including short-term ex vivo vibrissae explants, innovative mouse skin organoids (mSKOs), and human pluripotent stem cell-derived skin organoids (hSKOs), to monitor MC development. We demonstrate that Polycomb repressive complex inhibitors (PRCis) efficiently promote MC generation in these culture systems. Through single-cell and spatial transcriptomics analysis, together with pharmacological screening, we identify IGF1R as a potential regulator of MC formation, which likely exerts its effects through the AKT pathway. Furthermore, we validate the role of FGFR2 signaling in MC generation. These systems constitute a versatile platform that harnesses complementary strengths to not only advance MC biology and skin development but also enable stem cell research, supporting organoid-based disease modeling, therapeutic compound screening, and regenerative medicine.

CRX (cone-rod homeobox) is a key regulator of retinal photoreceptor development, yet its human-specific functions remain poorly understood due to scarce human retinal tissues and significant species differences. Here, we established a human CRX-mCherry fluorescent reporter retinal organoid (RO) model to dissect CRX-mediated gene regulation. Using FACS, RNA sequencing, and Cleavage Under Targets and Tagmentation (CUT&Tag) sequencing, we identified CRX target genes and revealed its dual regulatory role: it activates photoreceptor-specific genes (e.g., RP1L1, linked to inherited retinal degeneration) in a dose-dependent manner, while suppressing non-photoreceptor genes (e.g., PCDH8 and PROX1). Notably, we first generated the human CRX CUT&Tag dataset, providing direct insights into CRX's genome-wide regulatory landscape in photoreceptor cell development. These findings demonstrate that CRX functions as both a transcriptional activator and repressor, ensuring photoreceptor-specific gene expression and preventing aberrant cell fate transitions. Our study provides critical insights into the role of human CRX in retinal development and implications for retinal degenerative diseases.

Populations of adult neural stem cells (NSCs) that reside in the mammalian brain aid in neurogenesis throughout life and can be identified by a type VI intermediate filament protein, Nestin. Cell cycle regulation plays an important role in maintaining a balance between self-renewal and differentiation and determining the fate of NSCs. Data from our group and others support that the atypical cyclin-like protein SPY1 (also called RingoA; gene SPDYA) plays a critical role in activating NSCs from a quiescent state. Elevated levels of Spy1 are found in aggressive human brain cancers, including glioblastoma. Using a conditional mouse model, we demonstrate that driving the expression of Spy1, in the Nestin-enriched NSC population of the brain, increases stemness characteristics, decreases differentiation, and increases susceptibility to oncogenic transformation. This study contributes to better understanding of intricate cell cycle mechanisms that lead to deviation from the homeostatic state, promoting aberrant changes in adult NSCs.

Over the last 25 years, there has been tremendous progress in human pluripotent stem cell (hPSC) technology and clinical trials testing hPSC-derived products. The development of these hPSC-derived products requires the selection of a suitable hPSC line as the starting material for product manufacturing. The bespoke development of an hPSC line for product development can require significant time and resources. Given the acceleration of clinical trials testing hPSC-derived products, there is a growing need for available clinically and commercially suitable "off-the-shelf" hPSC lines. We have identified 166 clinical hPSC lines that are currently available for licensing and distribution. This paper provides details regarding these lines that may assist developers in preliminary evaluation of lines for use in clinical development.

In chronic myeloid leukemia (CML), disease persistence in patients is maintained by leukemic stem cells (LSCs), which drive tyrosine kinase inhibitor (TKI) resistance. Autophagy has been proposed as a potential therapy to eradicate CML LSCs. Here, using a small-molecule inhibitor of Hsp70 (heat shock protein 70)-Bim (Bcl-2-interacting mediator of cell death) interaction, S1-10, we demonstrate that Hsp70-Bim is a target for CML stemness maintenance. Hsp70-Bim is driven by Bcr-Abl and mediates particularly stronger mitophagy in CML LSCs than differentiated CML cells and HSCs. The more selective mitophagy regulation of Hsp70-Bim than ULK1 (unc-51-like autophagy activating kinase 1) is illustrated. Pharmacological inhibition of Hsp70-Bim blocks mitophagy, leading to the differentiation of CML LSCs, loss of quiescence, and loss of LSC self-renewal potential. In the patient-derived xenograft (PDX) CML models, S1g-10 reduces the number of LSCs by more than 80% after two weeks of injection, without obvious toxicity on normal red blood cells.

Asthma is a chronic inflammatory airway disease characterized by defective epithelial repair, resulting from metabolic dysregulation in facultative progenitor cells. Here, we investigate how pyruvate metabolism in airway club cells controls epithelial differentiation and allergic airway inflammation. Single-cell transcriptomics revealed elevated glycolytic activity in club and goblet cells from patients with asthma. In an ovalbumin (OVA)-induced asthma model, conditional deletion of Mpc2-but not Ldha-in club cells impaired club-to-goblet cell differentiation, reduced CLCA3 and Foxa3 expression, and attenuated eosinophilic inflammation and Il-13 expression. Mpc2 loss increased Cxcl17 expression in club cells, promoting Cxcl17-Cxcr4 signaling with alveolar macrophages that suppressed CCL17-mediated type 2 inflammation. Neutralizing CCL17 phenocopied the Mpc2 knockout by reducing airway inflammation and goblet cell differentiation. These findings reveal a metabolic-immune crosstalk underlying asthma pathogenesis and identify mitochondrial pyruvate metabolism as a therapeutic target to limit epithelial remodeling and type 2 inflammation.