Biology subjects

Lesch, B. J.

Publications and source records attributed to Lesch, B. J..

16 recordsLinked to original sources

bioRxiv2026

Paternal regulation of H3K4 methylation supports tumor suppressor networks in mammals intergenerationally

Paternally-inherited epigenetic information can influence phenotype in offspring (1). Here, we identify a critical mechanistic contribution of KDM6A (UTX), an X-linked histone modifier and tumor suppressor, in regulating transmissible epigenetic information in mammalian sperm. Paternal loss of KDM6A increases cancer risk in genetically wild type offspring, but how Kdm6a knockout sperm transmit this effect at the molecular level is unknown (2). We find that KDM6A functions in spermatogenesis to promote methylation of histone H3 lysine 4 (H3K4) via selective interaction with the COMPASS complex methyltransferase KMT2C (MLL3). KMT2C and KDM6A are coordinately recruited to promoters of active genes in spermatogenic cells, contrasting with recruitment to intergenic enhancers in other cell types (3, 4). Loss of KDM6A disrupts H3K4 methylation at promoters of tumor suppressor genes in spermatogonia, and some of these defects persist in epididymal sperm and correspond to impaired expression in preimplantation embryos. These genes are also misregulated in normal and malignant hematopoietic tissue of genetically wild type offspring, indicating that impaired H3K4 methylation in KDM6A-deficient male germ cells may preferentially alter regulation of tumor suppressor gene networks in development across generations.

genetics↗

bioRxiv2026

Ancestral chromatin state constrains the functional landscape of bivalent domains in mammalian spermatogenesis

Mammalian germ cells are enriched for bivalent chromatin, an epigenetic state defined by the dual presence of the activating H3K4me3 and repressive H3K27me3 histone modifications. Bivalency is evolutionarily conserved at developmentally important genes in germ cells but diverges at hundreds of additional loci, and evolutionary gains in bivalency have been proposed to reflect divergent somatic functions of the associated genes. Here, we sought to discover if evolutionary gains in bivalency occur selectively at genes with specific functions, and to better elucidate the role of bivalent chromatin in germ cells. By comparing genome-wide profiles for four histone modifications in spermatogenic cells of six mammalian species, we define a comprehensive set of mammalian bivalent domains and classify them based on conservation or divergence of chromatin state. We find that evolutionarily conserved bivalent regions exhibit canonical features of bivalency and maintain bivalency in embryonic stem cells. In contrast, bivalent domains emerging from a purely active or repressed ancestral chromatin state have atypical sequence and regulatory features and are frequently germ cell specific. Genes associated with these recent bivalent domains exhibit distinct somatic expression patterns that reflect their ancestral chromatin state in germ cells. Specifically, bivalent genes emerging from ancestrally active chromatin are more highly expressed in somatic tissues and are enriched for immune-related functions, while those emerging from ancestrally H3K27me3-only domains are lowly expressed in the soma and enriched for neurogenesis functions. We propose that recent bivalent regions demarcate sites of regulatory sequence change that preferentially impacts specific somatic lineages.

genomics↗

bioRxiv2026

Combinatorial base editing couples disease correction with lineage amplification in hematopoietic stem and progenitor cells

First-generation genome editing therapies have largely focused on correcting or compensating for pathogenic variants. However, as these approaches enter the clinic, emerging biological constraints limit maximal therapeutic impact. Because globin genes are activated late during erythroid differentiation, genome-corrected hematopoietic stem and progenitor cells (HSPCs) gain little selective advantage in the bone marrow. Here, we establish a strategy that links therapeutic genome edits to an erythroid fitness-enhancing allele to amplify the output of clinically relevant cells. We develop a multiplex base editing strategy that couples fetal hemoglobin (HbF) reactivation with erythroid lineage expansion. Introduction of a naturally occurring erythropoietin receptor truncation (tEPOR) associated with benign erythrocytosis increased erythroid cell production without impairing viability or differentiation. Combinatorial editing of tEPOR together with the BCL11A erythroid enhancer and HBG1/2 promoters in healthy donor, sickle cell disease, and {beta}-thalassemia HSPCs synergistically increased erythroid proliferation and HbF expression beyond single base-edited or Casgevy-treated controls. Multiplex base-edited HSPCs retained long-term lineage repopulation and engraftment capacity in vivo, establishing a modular strategy that pairs disease correction with lineage amplification to improve therapeutic potency.

cell biology↗

bioRxiv2026

Complementary constraints in germ and immune cells shape evolution of gene regulation and phenotype

New mutations arise in germ cells and must preserve fertility while altering somatic phenotype to confer a fitness advantage. To understand how whole organisms balance these constraints, we generated mice with humanized noncoding promoter sequence at Traf6, an NF-{kappa}B pathway component with recently diverged chromatin state in mouse germ cells. The humanized allele (Traf6h) reinstated human-like expression in germ and immune cells, which we traced to a 13 base pair deletion that impairs CTCF binding. Traf6h had no effect on fertility but induced a sensitized innate immune response to endotoxin. Other NF-{kappa}B pathway genes followed a similar pattern, suggesting that their expression has evolved in tandem and consistent with known mouse-human differences in inflammatory response. Our results reveal distinct roles for germ and immune cells in shaping gene regulatory evolution, where immune cells quickly adjust phenotype, enabling selection, while germ cells robustly maintain fertility despite changing expression levels, enabling inheritance.

genetics↗

bioRxiv2026

3D chromatin compartment of round spermatids encodes the spatiotemporal program of histone-to-protamine exchange in spermiogenesis

Sperm formation requires a radical chromatin reorganization, where nucleosomes are replaced by transition proteins (TNPs) and subsequently by protamines (PRM1 and PRM2). Although essential for fertility, the regulatory logic governing this exchange is unknown, but its presumed to be stochastic and unregulated. Using endogenously tagged PRM mouse models and stage-resolved, genome-wide profiling, we revise the order of histone-to-protamine exchange and show that the chromatin remodeling process is highly programmed. Imaging and biochemical experiments reveal a direct histone-to-PRM1 exchange, while TNPs appear after PRM1 but precede PRM2 incorporation. This temporal uncoupling of PRM1 and PRM2 incorporation coincides with dynamic, region-specific chromatin remodeling that is not governed by histone acetylation but is instructed by the three-dimensional nuclear architecture of round spermatids. Therefore, by integrating ATAC-seq, CUT&Tag, and Hi-C, we define a compartment-encoded "blueprint" that prescribes the assembly of the mature sperm epigenome and establishes a complex molecular hierarchy for the histone-to-protamine exchange.

genomics↗

bioRxiv2025

A human arteriovenous differentiation roadmap reveals vein developmental mechanisms and vascular effects of viruses

Extracellular signals and cell-fate trajectories during vein development remain elusive, despite trailblazing insights into artery development. Here we exploit human pluripotent stem cell differentiation and mouse embryology to present a model that answers longstanding questions: vein endothelial cell (EC) differentiation unfolds in two steps driven by opposing extracellular signals. First, VEGF differentiates mesoderm into "primed" ECs, newly-defined progenitors that co-express certain arterial (SOX17) and venous (APLNR) markers. Second, primed ECs execute vein differentiation upon VEGF/ERK inhibition; however, upon VEGF activation they can instead form artery ECs. The arteriovenous plasticity of primed ECs was supported by intersectional lineage tracing. Future venous genes including NR2F2 harbor poised chromatin in primed ECs, but are only transcribed upon VEGF/ERK inhibition. SOXF transcription factors, including SOX17, confer primed ECs with vein differentiation competence. Collectively, this two-step vein differentiation model--entailing primed EC intermediates and VEGF/ERK inhibition to trigger vein differentiation--has implications for VEGF-modulating therapies.

developmental biology↗

bioRxiv2025

Protamine lacunae preserve the paternal chromatin landscape in sperm

The transmission of the paternal genome requires extensive chromatin reorganization, in which nucleosomes are largely replaced by protamines that drive extreme condensation of the genome in the sperm head. Using Fiber-seq, we resolve patterns of paternal chromatin repackaging in sperm at single-molecule resolution, revealing the interplay between protamination and nucleosome retention. We find that nucleosome retention is probabilistic, with no locus universally occupied. Although promoters of spermatogenic genes preferentially harbor retained nucleosomes, the predominant carrier of paternal epigenetic information is protamine lacunae, accessible discontinuities in the protamine coat that preferentially mark critical regulatory elements. By contrast, centromere kinetochore binding regions robustly retain CENP-A mono-nucleosomes, providing a mechanism for the focal transmission of paternal centromeres. Finally, we find that paternal chromatin repackaging is altered in low-motility sperm. Together, these findings reveal distinct modes of paternal chromatin epigenetic inheritance with broad implications for development and infertility.

genomics↗

bioRxiv2025

H3K4me3 instructs transcription at intergenic active regulatory elements

Mammalian genomes undergo pervasive transcription in both genic and intergenic regions. Tri-methylation of histone H3 lysine 4 (H3K4me3) is a deeply conserved and functionally important histone modification enriched at transcriptionally active promoters, where it facilitates RNA polymerase activity. H3K4me3 is also commonly found in intergenic regions, where its role is poorly understood. We interrogated the role of H3K4me3 at intergenic regulatory elements by using epigenetic editing to efficiently deposit H3K4me3 at intergenic loci. We find that H3K4me3 instructs RNA polymerase activity and is actively remodeled at intergenic regions, shedding light on these important but poorly understood regions of the genome.

genetics↗

bioRxiv2024

ISWI chromatin remodeler SMARCA5 is essential for meiotic gene expression and male fertility in mammals

Regulation of the transcriptome to promote meiosis is important for sperm development and fertility. However, how chromatin remodeling directs the transcriptome during meiosis in male germ cells is largely unknown. Here, we demonstrate that the ISWI family ATP-dependent chromatin remodeling factor SMARCA5 (SNF2H) plays a critical role in regulating meiotic prophase progression during spermatogenesis. Males with germ cell-specific depletion of SMARCA5 are infertile and unable to form sperm. Loss of Smarca5 results in failure of meiotic progression with abnormal spermatocytes beginning at the pachytene stage and an aberrant global increase in chromatin accessibility, especially at genes important for meiotic prophase.

genetics↗

bioRxiv2024

Engineering inducible signaling receptors to enable erythropoietin-free erythropoiesis

Blood transfusion plays a vital role in modern medicine. However, availability is contingent on donated blood, and frequent shortages pose a significant healthcare challenge. Ex vivo manufacturing of red blood cells (RBCs) derived from universal donor O-negative pluripotent stem cells emerges as a solution, yet the high cost of recombinant cytokines required for ex vivo erythroid differentiation remains a major barrier. Erythropoietin (EPO) signaling through the EPO receptor is indispensable to RBC development, and EPO is one of the most expensive components in erythroid-promoting media. Here, we used design-build-test cycles to develop highly optimized small molecule-inducible EPO receptors (iEPORs) which were integrated at a variety of genomic loci using homology-directed repair genome editing. We found that integration of iEPOR at the endogenous EPOR locus in an induced pluripotent stem cell producer line enabled culture with small molecule to yield equivalent erythroid differentiation, transcriptomic changes, and hemoglobin production compared to cells cultured with EPO. Due to the dramatically lower cost of small molecules vs. recombinant cytokines, these efforts eliminate one of the most expensive elements of ex vivo culture media--EPO cytokine. Because dependence on cytokines is a common barrier to ex vivo cell production, these strategies could improve scalable manufacturing of a wide variety of clinically relevant cell types. More broadly, this work showcases how synthetic biology and genome editing may be combined to introduce precisely regulated and tunable behavior into cells, an advancement which will pave the way for increasingly sophisticated cell engineering strategies.

synthetic biology↗

bioRxiv2024

Combining Cell-Intrinsic and -Extrinsic Resistance to HIV-1 By Engineering Hematopoietic Stem Cells for CCR5 Knockout and B Cell Secretion of Therapeutic Antibodies

Autologous transplantation of CCR5 null hematopoietic stem and progenitor cells (HSPCs) is the only known cure for HIV-1 infection. However, this treatment is limited because of the rarity of CCR5-null matched donors, the morbidities associated with allogeneic transplantation, and the prevalence of HIV-1 strains resistant to CCR5 knockout (KO) alone. Here, we propose a one-time therapy through autologous transplantation of HSPCs genetically engineered ex vivo to produce both CCR5 KO cells and long-term secretion of potent HIV-1 inhibiting antibodies from B cell progeny. CRISPR-Cas9-engineered HSPCs maintain engraftment capacity and multi-lineage potential in vivo and can be engineered to express multiple antibodies simultaneously. Human B cells engineered to express each antibody secrete neutralizing concentrations capable of inhibiting HIV-1 pseudovirus infection in vitro. This work lays the groundwork for a potential one-time functional cure for HIV-1 through combining the long-term delivery of therapeutic antibodies against HIV-1 and the known efficacy of CCR5 KO HSPC transplantation.

bioengineering↗

bioRxiv2023

Evolutionary innovations in germline biology of placental mammals revealed by transcriptomics of first wave spermatogenesis in opossum

Mammalian spermatogenesis is a deeply conserved developmental program that is essential for fitness. Paradoxically, spermatogenic development also allows rapid divergence in gene expression and is thought to be a source of evolutionary novelty and gene birth. How mammalian spermatogenic cells protect a conserved developmental program while enabling exceptionally rapid divergence in gene expression and function is unknown. Here, we comprehensively profile the spermatogenic gene expression program in grey short-tailed opossum (Monodelphis domestica, a model marsupial) and compare it to equivalent data from the mouse (Mus musculus, a model placental mammal) to discover contrasting forces underlying the unique evolutionary dynamics of gene expression during mammalian spermatogenesis. For the first time, we describe the timing of the first wave of opossum spermatogenesis, and we combine bulk transcriptomic data from first-wave juvenile testes with single-cell transcriptomic data from adult testes to define conserved and divergent gene expression programs across the placental-marsupial split. We substantiate and extend our findings using genome-wide chromatin and multi-species transcriptome data and identify three classes of genes with different evolutionary trajectories: a deeply conserved central gene regulatory program governing spermatogenic progression; a separate class of spermatogenic genes exhibiting dynamic expression across placental mammals; and a third set of genes with evidence for directional selection in the placental mammal ancestor and constraint on expression levels within the placental mammalian lineage, representing placental innovations in germline gene expression and including biologically critical modules such as the DNA recombination and repair machinery.

genomics↗

bioRxiv2022

KDM6A/UTX promotes spermatogenic gene expression across generations but is dispensable for male fertility

Paternal chromatin undergoes extensive structural and epigenetic changes during mammalian spermatogenesis, producing sperm that contain an epigenome optimal for the transition to embryogenesis. Histone modifiers play an important role in this process by encoding specialized regulatory information in the sperm epigenome. Lysine demethylase 6a (KDM6A) promotes gene activation via demethylation of H3K27me3, a developmentally important repressive modification abundant throughout the epigenome of sperm and embryonic stem cells. Despite its developmental importance in pluripotent cells and germ cell progenitors, the function of KDM6A during spermatogenesis has not been described. Here, we show that Kdm6a is transiently expressed in the male germline in late spermatogonia and during the early stages of meiotic entry. Deletion of Kdm6a in the male mouse germline (Kdm6a cKO) yielded a modest increase in sperm head defects but did not affect fertility or the overall progression of spermatogenesis. However, hundreds of genes were deregulated upon loss of Kdm6a in spermatogenic cells and in an immortalized spermatogonia cell line (GC-1 spg) with a strong bias towards downregulation. Single cell RNA-seq revealed that most of these genes were deregulated in spermatogenic cells at the same stage when Kdm6a is expressed and encode epigenetic factors involved in chromatin organization and modification. A subset of these genes was persistently deregulated in the male germ line across two generations of offspring of Kdm6a cKO males. Our findings highlight KDM6A as a transcriptional activator in the mammalian male germline that is dispensable for spermatogenesis but important for safeguarding gene regulatory state intergenerationally. Author summaryOffspring viability and fitness relies upon the development of functional sperm and the integrity of information that they carry. Chromatin is modified and remodeled extensively throughout spermatogenesis to facilitate meiosis, DNA compaction, and to encode gene regulatory information for the next generation. In mice, a paternal germline lacking KDM6A, a histone modifier, yields offspring with reduced lifespans and increased cancer risk. How KDM6A functions in the paternal germline to support offspring health is unknown. Here, we show that Kdm6a expression is limited to a distinct developmental interval when differentiated spermatogonia transition from mitosis to meiosis. During this timepoint, KDM6A acts as a transcriptional activator for hundreds of genes, many of which encode meiotic factors and epigenetic modifiers. Nevertheless, this activity is dispensable for overall spermatogenesis and fertility. Surprisingly, we find a significant overlap in germline transcriptomes of Kdm6a cKO mice and wildtype offspring. We propose that KDM6A encodes gene regulatory information in the male germline that is retained across generations.

genetics↗

bioRxiv2021

DOT1L bridges transcription and heterochromatin formation at pericentromeres

Repetitive DNA elements are packaged in heterochromatin, but many require bursts of transcription to initiate and maintain long-term silencing. The mechanisms by which these heterochromatic genome features are transcribed remain largely unknown. Here, we show that DOT1L, a conserved histone methyltransferase that modifies lysine 79 of histone H3 (H3K79), has a specialized role in transcription of major satellite repeats to maintain pericentromeric heterochromatin and genome stability. We discover that H3K79me3 is enriched at repetitive elements, that DOT1L loss specifically compromises pericentromeric satellite transcription, and that this function depends on interaction between DOT1L and the chromatin remodeler SMARCA5. Activation of pericentromeric repeats by DOT1L drives the first establishment of heterochromatin structures in cleavage-stage embryos and is required for preimplantation viability. Our findings uncover a vital instructive role for DOT1L as a bridge between transcriptional activation of heterochromatic repeats and maintenance of genome integrity, and illuminate global chromatin dynamics during early development.

molecular biology↗

bioRxiv2021

A nuclear role for the Argonaute protein AGO2 in mammalian gametogenesis

Argonaute 2 (AGO2) is a ubiquitously expressed protein critical for regulation of mRNA translation and vital to animal development. AGO2 protein is found in both cytoplasmic and nuclear compartments, and while its cytoplasmic role is well studied, the biological relevance of nuclear AGO2 is unclear. Here, we address this problem in vivo, using developing spermatogenic cells as a model. Remarkably, we find that AGO2 acts in the germ cell nucleus to positively regulate protein expression. We show that AGO2 dynamically binds both chromatin and nuclear mRNA transcripts of hundreds of genes required for sperm production, and germline conditional knockout (cKO) of Ago2 causes depletion of the corresponding proteins, along with defects in sperm number and morphology. Nuclear AGO2 partners with splicing, export, and chromatin factors to promote transcript export and protein expression. Together, our data reveal an unexpected role for nuclear AGO2 in enhancing expression of developmentally important genes.

developmental biology↗

bioRxiv2020

Gene replacement of α-globin with β-globin restores hemoglobin balance in β-thalassemia-derived hematopoietic stem and progenitor cells

{beta}-thalassemia pathology is not only due to loss of {beta}-globin (HBB), but also erythrotoxic accumulation and aggregation of the {beta}-globin binding partner, -globin (HBA1/2). Here we describe a Cas9/AAV6-mediated genome editing strategy that can replace the entire HBA1 gene with a full-length HBB transgene in {beta}-thalassemia-derived hematopoietic stem and progenitor cells (HSPCs), which is sufficient to normalize {beta}-globin:-globin mRNA and protein ratios and restore functional adult hemoglobin tetramers in patient-derived red blood cells. Edited HSPCs were capable of long-term and bi-lineage hematopoietic reconstitution in mice, establishing proof-of-concept for replacement of HBA1 with HBB as a novel therapeutic strategy for curing {beta}-thalassemia.

molecular biology↗