Retrotransposons are co-opted to activate hematopoietic stem cells and erythropoiesis

Comparison of routine blood parameters by altitude and residence duration in the Western Sichuan Plateau

Background

This study explores how routine blood test parameters change over time in acclimatized individuals at different altitudes on the Western Sichuan Plateau.

Methods

Healthy men aged 20-40 from low-altitude areas who moved to Ganzi Prefecture to live and work were recruited. The observation sites were Guzan Town (1400 m), Kangding County Seat (2500 m), Luhuo County Seat (3400 m), and Litang County Seat (4100 m). Participants at the same altitude were grouped according to residence duration. The relationships between blood test parameters, altitude, and residence duration were analyzed.

Results

After moving to the plateau, white blood cell, red blood cell, hemoglobin, and hematocrit levels rose quickly in the short term, then declined and stabilized. In contrast, platelet levels increased steadily and were positively correlated with altitude.

Conclusions

Changes in blood parameters during high-altitude acclimatization are significant physiological responses to hypoxia and are affected by both altitude and residence duration.

Clinical response to azacitidine in MDS is associated with distinct DNA methylation changes in HSPCs

Hypomethylating agents are frontline therapies for myelodysplastic neoplasms (MDS), yet clinical responses remain unpredictable. We conducted a phase 2 trial comparing injectable and oral azacitidine (AZA) administered over one or three weeks per four-week cycle, with the primary objective of investigating whether response is linked to in vivo drug incorporation or DNA hypomethylation. Our findings show that injection results in higher drug incorporation, but lower DNA demethylation per cycle, while global DNA methylation levels in mononuclear cells are comparable between responders and non-responders. However, hematopoietic stem and progenitor cells (HSPCs) from responders exhibit distinct baseline and early treatment-induced CpG methylation changes at regulatory regions linked to tissue patterning, cell migration, and myeloid differentiation. By cycle six-when clinical responses typically emerge-further differential hypomethylation in responder HSPCs suggests marrow adaptation as a driver of improved hematopoiesis. These findings indicate that intrinsic baseline and early drug-induced epigenetic differences in HSPCs may underlie the variable clinical response to AZA in MDS.

Distinct type I and II interferon responses direct cortical and medullary thymic epithelial cell development

Advances in genomics have redefined our understanding of thymic epithelial heterogeneity and architecture, yet signals driving thymic epithelial differentiation remain incompletely understood. Here, we elucidated pathways instructing human thymic epithelial cell development in the context of other anterior foregut-derived organs. Activation of interferon response gene regulatory networks distinguished epithelial cells of the thymus from those of other anterior foregut-derived organs. Thymic cortex and medulla epithelia displayed distinctive interferon-responsive signatures defined by lineage-specific chromatin accessibility. We explored the effects of type I and II interferons on thymic epithelial progenitor differentiation from induced pluripotent stem cells. Type II interferon was essential for expressing proteasome and antigen-presenting molecules, whereas type I or II interferons were essential for inducing different cytokines in thymic epithelial progenitor cells. Our findings suggest that interferons are critical to cortical and medullary thymic epithelial cell differentiation.

STING mediates increased self-renewal and lineage skewing in DNMT3A-mutated hematopoietic stem/progenitor cells

Somatic mutations in DNA methyltransferase 3 A (DNMT3A) are frequently observed in patients with hematological malignancies. Hematopoietic stem/progenitor cells (HSPCs) with mutated DNMT3A demonstrate increased self-renewal activity and skewed lineage differentiation. However, the molecular mechanisms underlying these changes remain largely unexplored. In this study, we show that Dnmt3a loss leads to the upregulation of endogenous retroviruses (ERVs) in HSPCs, subsequently activating the cGAS-STING pathway and triggering inflammatory responses in these cells. Both genetic and pharmacological inhibition of STING effectively corrects the increased self-renewal activity and differentiation skewing induced by Dnmt3a deficiency in mice. Notably, targeting STING showed inhibited acute myeloid leukemia (AML) development in a Dnmt3a-KO; Flt3-ITD AML model, comparable to AC220, an FDA-approved FLT3-ITD inhibitor. A patient-derived xenograft (PDX) model further demonstrated that targeting STING effectively alleviates the leukemic burden of DNMT3A-mutant AML. Collectively, our findings highlight a critical role for STING in hematopoietic disorders induced by DNMT3A mutations and propose STING as a potential therapeutic target for preventing the progression of DNMT3A mutation-associated leukemia.