Biology subjects

Wang, H. C.

Publications and source records attributed to Wang, H. C..

6 recordsLinked to original sources

bioRxiv2025

MLL3 and MLL4 sustain hematopoietic stem cell multipotency by opposing a B-cell default state

Hematopoietic stem cells (HSCs) and multipotent progenitors (MPPs) are sustained by networks of transcription factors and epigenetic regulators that prime lineage-specific programs yet maintain multipotency. Two epigenetic regulators, MLL3 and MLL4, play important but opposing roles in maintaining this balance. MLL3 promotes HSC differentiation, whereas MLL4 opposes differentiation. These opposing functions are essential for both normal homeostasis and leukemia suppression, yet it is not clear how MLL3 and MLL4 regulate HSC and MPP gene expression to control HSC/MPP fate decisions. To resolve these mechanisms, we performed an extensive series of single cell genomic studies after conditionally deleting Mll3, Mll4 or both genes together. Mll3 deletion had only limited effects on HSC/MPP enhancer networks at steady state, whereas Mll4 deletion led to precocious activation of myeloid enhancers. Surprisingly, compound Mll3/4 deletion eliminated all myeloid, erythroid and megakaryocytic potential within the hematopoietic hierarchy and caused all progenitors to rapidly default to a B-cell-like identity. These changes were accompanied by widespread inactivation of HSC/MPP enhancers and superenhancers, and ectopic activation of B-cell superenhancers. Disabling MLL3/4 histone methyltransferase activity did not recapitulate the pervasive changes in cell identity that were observed when MLL3 and MLL4 were fully inactivated, indicating that MLL3 and MLL4 activate HSC/MPP enhancers independently from their enzymatic activities. Our findings show that HSC/MPP multipotency requires sustained tension between MLL3/4-dependent enhancers that maintain myeloid, erythroid and megakaryocyte potential, and MLL3/4-independent enhancers that prime B-cell identity. MLL3 and MLL4 therefore serve as critical linchpins of multilineage hematopoiesis. KEY POINTSO_LIMLL3 and MLL4 act redundantly in HSCs to sustain transcription factor and enhancer networks that support multipotency C_LIO_LISimultaneous loss of MLL3 and MLL4 drives hematopoietic progenitors into a uniform B-cell-like default state C_LI

cell biology↗

bioRxiv2025

Proteostasis Stress Drives Stem Cell Aging, Clonal Hematopoiesis and Leukemia

Aging is the primary risk factor for clonal hematopoiesis and the development of hematologic malignancies (1-5), yet the selective pressures that shape stem cell behavior and clonal expansion during aging remain poorly defined. Here, we identify proteostasis stress as a central driver of hematopoietic stem cell (HSC) aging and clonal evolution. We show that Heat shock factor 1 (Hsf1) is activated in aging HSCs to preserve proteostasis and sustain self-renewal. However, this physiological, age-associated adaptive mechanism is co-opted by pre-leukemic Dnmt3a-mutant HSCs to resist proteostasis and inflammatory stress required to fuel clonal expansion during aging. In the context of co-occurring Dnmt3a and Nras mutations, which are frequently observed in human acute myeloid leukemia (AML) (6-13), mutant HSCs and progenitors exhibit heightened dependence on Hsf1 for expansion, malignant transformation and disease progression. Loss of Hsf1, or disruption of proteostasis, impairs expansion of mutant progenitors, delays leukemia onset, and prolongs survival. Together, these findings reveal proteostasis as a key constraint in the aging hematopoietic system that imposes a selective bottleneck. Hsf1 activation enables both physiological adaptation in aging stem cells and pathological clonal outgrowth in pre-leukemic and leukemic states, establishing proteostasis control as a pivotal mechanism linking stem cell aging to clonal hematopoiesis and malignancy.

cancer biology↗

bioRxiv2022

Multiomic single-cell lineage tracing to dissect fate-specific gene regulatory programs

Complex gene regulatory mechanisms underlie differentiation and reprogramming. Contemporary single-cell lineage tracing (scLT) methods use expressed, heritable DNA barcodes to combine cell lineage readout with single-cell transcriptomics enabling high-resolution analysis of cell states while preserving lineage relationships. However, reliance on transcriptional profiling limits their adaptation to an ever-expanding tool kit of multiomic single-cell assays. With CellTag-multi, we present a novel approach for independently profiling lineage barcodes with single-cell chromatin accessibility without relying on co-assay of transcriptional state, paving the way for truly multiomic lineage tracing. We validate CellTag-multi in mouse hematopoiesis, characterizing transcriptional and epigenomic lineage priming across progenitor cell populations. In direct reprogramming of fibroblasts to endoderm progenitors, we use CellTag-multi to comprehensively link early cell state with reprogramming outcomes, identifying core regulatory programs underlying on-target and off-target reprogramming. Further, we reveal the Transcription Factor (TF) Zfp281 as a novel regulator of reprogramming outcome, biasing cells towards an off-target mesenchymal fate via its regulation of TGF-{beta} signaling. Together, these results establish CellTag-multi as a novel lineage tracing method compatible with multiple single-cell modalities and demonstrate its utility in revealing fate-specifying gene regulatory changes across diverse paradigms of differentiation and reprogramming.

genomics↗

bioRxiv2022

Basal type I interferon signaling has only modest effects on neonatal and juvenile hematopoiesis

Type I interferon (IFN-1) regulates gene expression and hematopoiesis both during development and in response to inflammatory stress. We previously showed that during development, hematopoietic stem cells (HSCs) and multipotent progenitors (MPPs) induce IFN-1 target genes shortly before birth in mice. This coincides with the onset of a transition to adult hematopoiesis, and it drives expression of genes associated with antigen presentation. However, it is not clear whether perinatal IFN-1 modulates hematopoietic output, as has been observed in contexts of inflammation. We have characterized hematopoiesis at several different stages of blood formation, from HSCs to mature blood cells, and found that loss of the IFN-1 receptor (IFNAR1) leads to depletion of several phenotypic HSC and MPP subpopulations in neonatal and juvenile mice. Committed lymphoid and myeloid progenitor populations simultaneously expand. These changes had surprisingly little effect on production of more differentiated blood cells. Cellular Indexing of Transcriptomes and Epitopes by sequencing (CITE-seq) resolved the discrepancy between the extensive changes in progenitor numbers and modest changes in hematopoiesis, revealing stability in most MPP populations in Ifnar1-deficient neonates when the populations were identified based on gene expression rather than surface marker phenotype. Thus, basal IFN-1 signaling has only modest effects on hematopoiesis. Discordance between transcriptionally- and phenotypically-defined MPP populations may impact interpretations of how IFN-1 shapes hematopoiesis in other contexts, such as aging or inflammation. KEY POINTSO_LILoss of type I Interferon signaling in neonatal mice depletes immature blood progenitors without compromising postnatal hematopoiesis C_LIO_LIProgenitor populations remain intact when measured by single cell transcriptomes rather than surface marker phenotypes C_LI

cell biology↗

bioRxiv2019

Purinergic signaling in cochlear supporting cells reduces hair cell excitability by increasing the extracellular space

Neurons in developing sensory pathways exhibit spontaneous bursts of electrical activity that are critical for survival, maturation and circuit refinement. In the auditory system, intrinsically generated activity arises within the cochlea, but the molecular mechanisms that initiate this activity remain poorly understood. We show that burst firing of mouse inner hair cells prior to hearing onset requires P2RY1 autoreceptors expressed by inner supporting cells. P2RY1 activation triggers K+ efflux and depolarization of hair cells, as well as osmotic shrinkage of supporting cells that dramatically increased the extracellular space and speed of K+ redistribution. Pharmacological inhibition or genetic disruption of P2RY1 suppressed neuronal burst firing by reducing K+ release, but unexpectedly enhanced their tonic firing, as water resorption by supporting cells reduced the extracellular space, slowing K+ clearance. These studies indicate that purinergic signaling in supporting cells regulates hair cell excitability by controlling the volume of the extracellular space.

neuroscience↗

bioRxiv2019

Whisker map organization in somatosensory cortex of awake, behaving mice

The whisker map in rodent somatosensory cortex is well characterized under anesthesia, but its organization during awake sensation, when cortical coding can differ strongly, is unknown. Using a novel behavioral task, we measured whisker receptive fields and maps in awake mice with 2-photon calcium imaging in vivo. During a whisker-attentive task, layer 2/3 pyramidal neurons were sharply tuned, with cells tuned to different whiskers intermixed in each column. This salt-and-pepper organization consisted of small clusters of similarly-tuned neurons superimposed on a mean subcolumnar map. Parvalbumin interneurons had broader tuning, and were more homogeneously tuned to the columnar whisker. During a sound-attentive task, whisker tuning of pyramidal cells was less heterogeneous in each column, and firing correlations increased. Thus, behavioral demands modulate fine-scale map structure, and decorrelate the whisker map during whisker-attentive behavior.

neuroscience↗