縄井 バハテヤリラヒムトラ

Hematopoietic stem cells (HSCs) exhibit significant age-related phenotypic and functional alterations. Although single-cell technologies have elucidated age-related compositional changes, prospective identification of aging-associated HSC subsets has remained challenging. In this study, utilizing Clusterin (Clu)-GFP reporter mice, we demonstrated that Clu expression faithfully marks age-associated myeloid/platelet-biased HSCs throughout life. Clu-GFP expression clearly segregates a novel age-associated HSC subset that overlaps with but is distinct from those previously identified using antibodies against aging maker proteins or reporter systems of aged HSC signature genes. Clu-positive (Clu+) HSCs emerge as a minor population in the fetus and progressively expand with age. Clu+ HSCs display not only an increased propensity for myeloid/platelet-biased differentiation but also a unique behaviour in the BM, favouring self-renewal over differentiation into downstream progenitors. In contrast, Clu-negative (Clu-) HSCs exhibit lineage-balanced differentiation, which predominates in the HSC pool during development but becomes underrepresented as aging progresses. Both subsets maintain long-term self-renewal capabilities even in aged mice but contribute differently to hematopoiesis. The predominant expansion of Clu+ HSCs largely drives the age-related changes observed in the HSC pool. Conversely, Clu- HSCs preserve youthful functionality and molecular characteristics into old age. Consequently, progressive changes in the balance between Clu+ and Clu- HSC subsets account for HSC aging. Our findings establish Clu as a novel marker for identifying aging-associated changes in HSCs and provide a new approach that enables lifelong tracking of the HSC aging process.

The H3K4 methyltransferase SETD1A plays an essential role in both development and cancer. However, essential components involved in SETD1A chromatin binding remain unclear. Here, we discovered that BOD1L exhibits the highest correlated SETD1A co-dependency in human cancer cell lines. BOD1L knockout reduces leukemia cells in vitro and in vivo, and mimics the transcriptional profiles observed in SETD1A knockout cells. The loss of BOD1L immediately reduced SETD1A distribution at transcriptional start sites (TSS), induced transcriptional elongation defect, and increased the RNA polymerase II content at TSS; however, it did not reduce H3K4me3. The Shg1 domain of BOD1L has a DNA binding ability, and a tryptophan residue (W104) in the domain recruits SETD1A to chromatin through the association with SETD1A FLOS domain. In addition, the BOD1L-SETD1A complex associates with transcriptional regulators, including E2Fs. These results reveal that BOD1L mediates chromatin and SETD1A, and regulates the non-canonical function of SETD1A in transcription.

Enhancer cis-regulatory elements play critical roles in gene regulation at many stages of cell growth. Enhancers in cancer cells also regulate the transcription of oncogenes. In this study, we performed a comprehensive analysis of long-range chromatin interactions, histone modifications, chromatin accessibility and expression in two gastric cancer (GC) cell lines compared to normal gastric epithelial cells. We found that GC-specific enhancers marked by histone modifications can activate a population of genes, including some oncogenes, by interacting with their proximal promoters. In addition, motif analysis of enhancer-promoter interacting enhancers showed that GC-specific transcription factors are enriched. Among them, we found that MYB is crucial for GC cell growth and activated by the enhancer with an enhancer-promoter loop and TCF7 upregulation. Clinical GC samples showed epigenetic activation of enhancers at the MYB locus and significant upregulation of TCF7 and MYB, regardless of molecular GC subtype and clinicopathological factors. Single-cell RNA sequencing of gastric mucosa with intestinal metaplasia showed high expression of TCF7 and MYB in intestinal stem cells. When we inactivated the loop-forming enhancer at the MYB locus using CRISPR interference (dCas9-KRAB), GC cell growth was significantly inhibited. In conclusion, we identified MYB as an oncogene activated by a loop-forming enhancer and contributing to GC cell growth.