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Background: Hypertension or elevated blood pressure (BP) is a worldwide clinical challenge and the leading primary risk factor for kidney dysfunctions, heart failure, and cerebrovascular disease. The kidney is a central regulator of BP by maintaining sodium-water balance. Multiple genome-wide association studies revealed that BP is a heritable quantitative trait, modulated by several genetic, epigenetic, and environmental factors. The SNPs identified in genome-wide association studies predominantly (>95%) reside within noncoding genomic regions, making it difficult to understand how they regulate BP. Given the central role of the kidney in regulating BP, we hypothesized that chromatin-accessible regions in renal tissue would be enriched for BP-associated single nucleotide polymorphisms., Methods: We manually dissected 2 important kidney segments that maintain the sodium-water balance: proximal tubules and medullary thick ascending limbs from the human and rat kidneys. To delineate their chromatin and transcriptomic profiles, we performed the assay for transposase-accessible chromatin and RNA sequencing, respectively., Results: The chromatin accessibility maps revealed the shared and unique cis -regulatory elements that modulate the chromatin accessibility in proximal tubule and medullary thick ascending limbs of humans and rats. We developed a visualization tool to compare the cross-species epigenomic maps to identify potential regulatory targets for hypertension pathogenesis. We also identified a significant enrichment of BP-associated single nucleotide polymorphisms (1064 for human proximal tubule and 1172 for human medullary thick ascending limbs) within accessible chromatin regions of both segments, including rs1173771 and rs1421811 at the NPR3 locus and rs1800470 at the TGFb1 locus., Conclusions: Collectively, this study lays a foundation for interrogating how intergenic single nucleotide polymorphisms may regulate polygenic traits such as BP.

The Switch/Sugar non-fermenting (SWI/SNF) nucleosome remodeling complexes are essential for normal hematopoiesis. The Brg1/Brm associated factor (BAF) is a form of mammalian SWI/SNF that is distinguished by the presence of either ARID1A or ARID1B protein. In this study, we used hematopoietic specific Cre mouse models to assess the function of Arid1b in blood development. We found Arid1b loss did not affect steady state hematopoiesis or hematopoietic regeneration. Nonetheless, Arid1b null hematopoietic stem and progenitor cells have reduced ability to reconstitute hematopoietic system compared to wild type cells. Overall, our data indicate Arid1b is largely dispensable for normal hematopoiesis but impairs the regenerative ability of HSPCs., Competing Interests: The authors have declared that no competing interests exist., (Copyright: © 2024 Arnold et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.)

Essential hypertension, a multifaceted disorder, is a worldwide health problem. A complex network of genetic, epigenetic, physiological, and environmental components regulates blood pressure (BP), and any dysregulation of this network may result in hypertension. Growing evidence suggests a role for epigenetic factors in BP regulation. Any alterations in the expression or functions of these epigenetic regulators may dysregulate various determinants of BP, thereby promoting the development of hypertension. Histone posttranslational modifications are critical epigenetic regulators that have been implicated in hypertension. Several studies have demonstrated a clear association between the increased expression of some histone-modifying enzymes, especially HDACs (histone deacetylases), and hypertension. In addition, treatment with HDAC inhibitors lowers BP in hypertensive animal models, providing an excellent opportunity to design new drugs to treat hypertension. In this review, we discuss the potential contribution of different histone modifications to the regulation of BP., Competing Interests: Disclosures None.

Objective As cohesin mutations are rarely found in MLL-rearranged acute myeloid leukemias, we investigated the potential synthetic lethality between cohesin mutations and MLL-AF9 using murine hematopoietic stem and progenitor cells. Results Contrary to our hypothesis, a complete loss of Stag2 or haploinsufficiency of Smc3 were well tolerated in MLL-AF9-expressing hematopoietic stem and progenitor cells. Minimal effect of cohesin subunit loss on the in vitro self-renewal of MLL-AF9-expressing cells was observed. Despite the differing mutational landscapes of cohesin-mutated and MLL fusion AMLs, previous studies showed that cohesin and MLL fusion mutations similarly drive abnormal self-renewal through HOXA gene upregulation. The utilization of a similar mechanism suggests that little selective pressure exists for the acquisition of cohesin mutations in AMLs expressing MLL fusions, explaining their lack of co-occurrence. Our results emphasize the importance of using genetic models to test suspected synthetic lethality and suggest that a lack of co-occurrence may instead point to a common mechanism of action between two mutations.

Acute myeloid leukemia (AML) is driven by mutations that occur in numerous combinations. A better understanding of how mutations interact with one another to cause disease is critical to developing targeted therapies. Approximately 50% of patients that harbor a common mutation in NPM1 (NPM1cA) also have a mutation in the cohesin complex. As cohesin and Npm1 are known to regulate gene expression, we sought to determine how cohesin mutation alters the transcriptome in the context of NPM1cA. We utilized inducible Npm1 cAflox/+ and core cohesin subunit Smc3 flox/+ mice to examine AML development. While Npm1 cA/+ ;Smc3 Δ/+ mice developed AML with a similar latency and penetrance as Npm1 cA/+ mice, RNA-seq suggests that the Npm1 cA/+ ; Smc3 Δ/+ mutational combination uniquely alters the transcriptome. We found that the Rac1/2 nucleotide exchange factor Dock1 was specifically upregulated in Npm1 cA/+ ;Smc3 Δ/+ HSPCs. Knockdown of Dock1 resulted in decreased growth and adhesion and increased apoptosis only in Npm1 cA/+ ;Smc3 Δ/+ AML. Higher Rac activity was also observed in Npm1 cA/+ ;Smc3 Δ/+ vs. Npm1 cA/+ AMLs. Importantly, the Dock1/Rac pathway is targetable in Npm1 cA/+ ;Smc3 Δ/+ AMLs. Our results suggest that Dock1/Rac represents a potential target for the treatment of patients harboring NPM1cA and cohesin mutations and supports the use of combinatorial genetics to identify novel precision oncology targets., (© 2022. The Author(s), under exclusive licence to Springer Nature Limited.)

Survival outcomes for relapsed/refractory pediatric acute myeloid leukemia (R/R AML) remain dismal. Epigenetic changes can result in gene expression alterations which are thought to contribute to both leukemogenesis and chemotherapy resistance. We report results from a phase I trial with a dose expansion cohort investigating decitabine and vorinostat in combination with fludarabine, cytarabine, and G-CSF (FLAG) in pediatric patients with R/R AML [NCT02412475]. Thirty-seven patients enrolled with a median age at enrollment of 8.4 (range, 1-20) years. There were no dose limiting toxicities among the enrolled patients, including two patients with Down syndrome. The recommended phase 2 dose of decitabine in combination with vorinostat and FLAG was 10 mg/m 2 . The expanded cohort design allowed for an efficacy evaluation and the overall response rate among 35 evaluable patients was 54% (16 complete response (CR) and 3 complete response with incomplete hematologic recovery (CRi)). Ninety percent of responders achieved minimal residual disease (MRD) negativity (<0.1%) by centralized flow cytometry and 84% (n = 16) successfully proceeded to hematopoietic stem cell transplant. Two-year overall survival was 75.6% [95%CI: 47.3%, 90.1%] for MRD-negative patients vs. 17.9% [95%CI: 4.4%, 38.8%] for those with residual disease (p < .001). Twelve subjects (34%) had known epigenetic alterations with 8 (67%) achieving a CR, 7 (88%) of whom were MRD negative. Correlative pharmacodynamics demonstrated the biologic activity of decitabine and vorinostat and identified specific gene enrichment signatures in nonresponding patients. Overall, this therapy was well-tolerated, biologically active, and effective in pediatric patients with R/R AML, particularly those with epigenetic alterations., (© 2022 Wiley Periodicals LLC.)