Abstract 2456: Transcriptional signatures of stem cell phenotypes in normal and clonal hematopoiesis

Abstract Clonal hematopoiesis (CH) is an age-related clonal expansion of hematopoietic stem cells (HSCs). Factors that shape the progression of CH are only beginning to be characterized. HSCs are a heterogeneous population of cells with distinct clonal outputs over time, which are hypothesized to be largely scripted in epigenetic and transcriptional cell state. Molecular properties of HSC states that mediate clonal behaviors of two major driver mutations in CH - DNMT3A and TET2 - represent potential therapeutical targets. Recent studies have identified the landscape of human CH mutant cells compared to non-mutated ones. However, the notion of a specific molecular target identified in CH cells associated with selective advantage or predisposition for subsequent transformation requires a formal validation by longitudinal studies. To uncover molecular underpinnings of CH-driven clonal phenotypes in human HSCs in vivo, we combined clonal analysis using heritable expressed DNA barcodes with single-cell transcriptomics using transplant in immunodeficient mice. We developed a statistical approach to associate transcriptional differences of HSCs with the clone phenotypes, such as size and HSC density, across more than a hundred of detected clones. It revealed robust transcriptional signatures underlying clone size and HSC density, which are largely complementary to transcriptional programs activated in TET2 and DNMT3A mutant HSCs. Of note, the clone size and density of HSCs in the clone tend to be uncoupled and associated with distinct transcriptional processes. Citation Format: Ruslan Soldatov, Giulia Schiroli, Peter Kharchenko, David Scadden. Transcriptional signatures of stem cell phenotypes in normal and clonal hematopoiesis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 2456.