Biology subjects

Xavier Raj, I.

Publications and source records attributed to Xavier Raj, I..

4 recordsLinked to original sources

bioRxiv2025

JAK2V617F Myeloproliferative Neoplasms Support Parallel Evolution of Independent Leukemic Clones

Myeloproliferative neoplasms (MPNs) are hematological diseases predominantly driven by the JAK2V617F mutation. Progression from chronic-phase MPN to secondary acute myeloid leukemia (sAML) is a severe complication that dramatically worsens disease prognosis. While progression to sAML is classically linked to MPN clones acquiring additional mutations, the absence of JAK2V617F in some cases of post-MPN sAML cases suggests alternative mechanisms of transformation. Utilizing patient samples and in vivo modeling, we establish that leukemic clones can emerge independently of JAK2-mutant cells and undergo positive selection in the pro-inflammatory MPN environment, leading to parallel disease evolution. Genetic and pharmacological inhibition of IL-12 and TNF mitigates this competitive advantage. Our data establish a new paradigm and show that disease progression in MPN can arise from parallel acute myeloid leukemia (pAML) clones.

cancer biology↗

bioRxiv2025

JARID2 Inhibition Reprograms Human Hematopoietic Progenitor Cells To Enhance Bone Marrow Transplantation

Hematopoietic stem cell transplantation is a common treatment for many blood disorders and can be a life-saving therapy for patients with leukemias, lymphomas and multiple myeloma. Umbilical cord blood (UCB) serves as a valuable source of hematopoietic stem and progenitor cells (HSPCs) for transplantation, particularly for patients lacking a matched donor. However, the limited number of repopulating cells in UCB units restricts its clinical utility. Our prior studies showed that genetic deletion of the polycomb repressive complex 2 (PRC2) co-factor Jarid2 in mouse multipotent progenitors (MPPs) conveyed ectopic self-renewal capacity. Here, we hypothesized that the function of human HSPCs could be enhanced through JARID2 inhibition. In this study, we demonstrate that both constitutive and transient knockdown of JARID2 increases the number and enhances the functionality of human HSPCs both in vitro and in vivo. This phenotype was distinct from inhibition of EZH2 in UCB cells, suggesting the mechanism was independent of PRC2 co-factor activity of JARID2. Mechanistically, JARID2 knockdown promotes a quiescent, long-term self-renewal gene expression program governed by upregulating STAT1 and characterized by an MHC class II immunophenotype. Analogous to mice, these mechanisms conferred HSC-like potential to human MPPs in vivo. Taken together, these findings highlight JARID2 inhibition as a novel and reversible approach to expand functional UCB-derived HSPCs ex vivo, potentially improving access to stem cell transplantation for a wider patient population. One Sentence SummaryGenetic inhibition of JARID2 enhances repopulating activity of human hematopoietic stem and progenitor cells in vivo via STAT1 upregulation.

developmental biology↗

bioRxiv2025

Functional Comparison to Ezh2 Reveals PRC2-Independent Functions of Jarid2 in Hematopoietic Stem Cell Lineage Commitment

Previous studies showed the Polycomb Repressive Complex 2 (PRC2) co-factor Jarid2 represses self-renewal transcriptional networks in mouse multipotent progenitor cells (MPPs). But only a fraction of de-repressed HSC-specific genes were associated with loss of H3K27me3, implying Jarid2 may have non-canonical (PRC2-indpendent) in hematopoiesis. Here we sought to delineate any PRC2-independnent functions by comparing stem and progenitor cells genetically deficient for either Jarid2 or Ezh2 (enzymatic component of PRC2). Loss of Ezh2 increased myeloid differentiation in transplantation assays. In contrast, loss of Jarid2 enhanced T-cell output. Single cell transcriptomics showed while loss of Jarid2 had minimal impact across progenitor populations, loss of Ezh2 led to accumulation of lymphoid-biased MPP4 cells and B-cell progenitors in the bone marrow. Functional assays confirmed a differentiation block at the pre-pro B-cell stage. The maturational arrest of Ezh2-deficient B-cell progenitors contrasts with increased T-cell output from loss of Jarid2, suggesting Jarid2 has non-canonical functions in hematopoiesis.

genetics↗

bioRxiv2020

Computer Designed PRC2 Inhibitor, EBdCas9, Reveals Functional TATA boxes in Distal Promoter Regions

The critical process in development, bifurcation of cellular fates, requires epigenetic H3K27me3 marks propagated by PRC2 complex. However, the precise chromatin loci of functional H3K27me3 marks are not yet known. Here we identify critical PRC2 functional sites at a single nucleosome resolution. We fused a computationally designed protein, EED binder (EB) that competes with EZH2 and thereby disrupts PRC2 function, to dCas9 (EBdCas9) to direct PRC2 inhibition at a precise locus using gRNA. We targeted EBdCas9 to 4 different genes (TBX18, p16, CDX2 and GATA3) and observed epigenetic remodeling at a single nucleosome resolution resulting in gene activation. Remarkably, while traditional TATA box is located 30bp upstream of TSS, we identified a functional TATA box, >500bp of TSS, normally repressed by PRC2 complex. Deletion of this TATA box eliminates EBdCas9 dependent TBP recruitment and transcriptional activation. Targeting EBdCas9 to CDX2 and GATA3 results in trophoblast trans-differentiation. EBdCas9 technology is broadly applicable for epigenetic regulation at a single locus to control gene expression. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=189 SRC="FIGDIR/small/385922v1_ufig1.gif" ALT="Figure 1"> View larger version (62K): org.highwire.dtl.DTLVardef@1da108borg.highwire.dtl.DTLVardef@17447ddorg.highwire.dtl.DTLVardef@11a188forg.highwire.dtl.DTLVardef@426022_HPS_FORMAT_FIGEXP M_FIG C_FIG

molecular biology↗