Biology subjects

Hwang, I.

Publications and source records attributed to Hwang, I..

At least 19 recordsLinked to original sources

bioRxiv2026

Disrupted Brain Organoid Circuitry, Structural Organization, and Spine Morphology in 7q11.23 Copy Number Variant Syndromes

The 7q11.23 chromosomal region represents a model of gene dosage-dependence, where a hemizygous deletion causes Williams Syndrome (WS) and a duplication leads to 7q11.23 Duplication Syndrome (Dup7). It is not understood how these copy number variations (CNVs) disrupt development and functional cortical circuit assembly. Utilizing iPSC-derived cerebral organoids and longitudinal imaging from post-differentiation day 30 to 150, we characterized the aberrant neural rosette morphogenesis in WS and Dup7 during early stages, establishing an early structural divergence from control lines. We observed accelerated early cortical rosette morphogenesis in WS, characterized by a premature increase in both rosette number and layer thickness compared to controls. In contrast, Dup7 organoids consistently exhibit a significantly lower number and reduced thickness of rosettes from early stages onward. This early structural disruption progressively impacted synaptic-level architecture as the organoids matured. Dendritic spine characterization at later stages revealed Dup7 organoids exhibited a significantly higher dendritic spine density compared to WS. Pharmacological antagonism of CCR5 (C-C chemokine receptor type 5) with Maraviroc significantly enhanced dendritic spine density in control and WS organoids; however, this effect was absent in Dup7. To determine how these structural anomalies translate into circuit-level behavior, we performed longitudinal calcium imaging using GCaMP. Control organoids sustained synchronized activity and high spike correlations at all time points. This synchronization was delayed and highly transient in WS organoids, and completely abolished in Dup7 organoids, which exhibit significantly low spike correlations at all stages. Developmentally, GABA changes from acting as an excitatory signal in the immature brain to an inhibitory signal as the brain matures. As control lines matured gabazine-induced desynchronization progressively diminished, but persisted in WS organoids. Dup7 organoids failed to establish synchronization at any developmental time point, but displayed a negligible increased synchrony following gabazine treatment. These functional aberrations were paralleled by genotype-specific defects in structural organization, specifically in rosette morphogenesis and dendritic spine density. Collectively, our findings demonstrate that 7q11.23 CNVs trigger pathogenic neurodevelopmental defects by derailing the trajectories of structural organization, circuit assembly, and functional synchronization during cortical maturation.

neuroscience↗

bioRxiv2026

POISE: Spectral Inference of Parent-of-Origin Effects in Unlabeled Genomic Data

MotivationParent of Origin Effects (POEs), where the effect of an an allele on a phenotype differs based on maternal or paternal inheritance implicated in growth, metabolism, and neurodevelopment. Traditional tests for POEs require family data to determine parental origins of transmitted alleles. Given that such studies are expensive and time consuming compared to genome-wide association studies (GWAS), tests that function absent inheritance information are highly desirable. We develop a method, based on community detection from machine learning, that infers POEs via a spectral decomposition, obtains confidence intervals via a non-parametric bootstrap, and safeguards against confounding by non POE sources of variation. We refer to our method as Parent of Origin Inference via Spectral Estimation (POISE). ResultsWe demonstrate that POISE is well-calibrated under both Gaussian and heavy-tailed noise in simulation studies, with improved robustness to true POEs compared to existing covariance-based tests. POISE provides per-trait effect estimates with bias-corrected bootstrap confidence intervals and incorporates an information-theoretic minimum detectable effect size that filters unreliable estimates, conferring robustness to covariance-deflating variance QTL. We then apply POISE to GWAS data from the UK Biobank using BMI, LDL cholesterol, and HDL cholesterol. POISE recovers established POE loci and identifies 134 additional variants at genes implicated in lipid metabolism, immune regulation, and growth. Availability and implementationThe code for this method in Python is available at https://github.com/bystrogenomics/POISE.

genetics↗

bioRxiv2026

Secreted phospholipase A2α generates a pathogen-derived lysophospholipid to signal local immunity

In plants, effector-triggered immunity (ETI) is initiated when NLR receptors recognize pathogen effectors, yet the molecular signals linking this recognition to downstream defense activation remain poorly defined, in contrast to the well-characterized immunogenic signals of pattern-triggered immunity. Here, we show that a lysophospholipid is a previously unidentified ETI-mediating immune signal generated through host enzymatic conversion of pathogen membrane lipids. Upon recognition of avirulent Pseudomonas syringae, secretory phospholipase A2 (PLA2) is rapidly induced and secreted into the apoplast, where it hydrolyzes bacterial phosphatidylethanolamine to produce lysophosphatidylethanolamines (LPEs), predominantly LPE18:1. Genetic ablation of PLA2 compromises local immunity, hypersensitive response confinement, and defense gene activation, all of which are largely rescued by exogenous LPE18:1. Mechanistically, LPE18:1 promotes ICS1-dependent salicylic acid biosynthesis and NPR1-mediated transcriptional reprogramming. Together, these findings support pathogen-derived LPE18:1 as a newly identified lipid-based immune signal that links NLR activation to spatially confined defense responses. The evolutionary conservation of secretory PLA2 enzymes and lysophospholipid signaling from plants to mammals suggests that host-directed enzymatic remodeling of pathogen membranes into immune-activating lipid signals may constitute a conserved strategy of innate immunity.

plant biology↗

bioRxiv2026

OmniDetect: a plant-produced universal IgG binder replacing secondary antibodies in immunoassays

High sensitivity in immunodetection technologies has long been a priority for both diagnostic kit development and routine laboratory research. We developed a recombinant fusion protein, OmniDetect-G3, as an alternative to conventional HRP-conjugated secondary antibodies, and successfully produced it in plants. OmniDetect-G3 binds to primary IgG antibodies regardless of host species, and also recognizes chicken IgY. In comparative analyses, OmniDetect-G3 exhibits 165-381% higher sensitivity than commercial secondary antibodies in western blot analysis and 30%-1145% higher sensitivity in ELISA, depending on commercial products tested. Moreover, OmniDetect-G3 showed robust performance when used with sera from vaccinated animals (porcine and bovine). The chemiluminescence signal generated by OmniDetect-G3 remained stable up to 30 minutes after reaction initiation. These findings indicate that plant-produced OmniDetect-G3 has strong potential as a universal mimetic to animal-derived HRP-conjugated secondary antibodies, offering simplified immunoassay workflows and improved detection efficiency.

immunology↗

bioRxiv2025

Progranulin loss induces mitochondrial dysfunction and ferroptosis in human cerebral organoids

Loss-of-function mutations in the granulin (GRN) gene cause frontotemporal dementia when the mutations are heterozygous and neuronal ceroid lipofuscinosis, a lysosomal storage disease, when homozygous. While it is well established that disease-causing GRN mutations decrease progranulin (PGRN) levels, leading to neurodegeneration, the cellular and molecular mechanisms underlying these conditions remain poorly understood. In this study, we utilized human induced pluripotent stem cell (iPSC) derived forebrain organoids to investigate the impact of PGRN homozygous deficiency on neuronal and glial cell populations. Through single-cell RNA sequencing, we identified robust downregulation of the mitochondrial oxidative phosphorylation pathway in PGRN KO organoids. In line with these results, PGRN KO organoids showed decreased mitochondrial respiration. Furthermore, our study demonstrated that PGRN loss induced increased levels of reactive oxygen species (ROS), lipid peroxidation and iron accumulation. Finally, we observed increased vulnerability to ferroptotic cell death in PGRN KO organoids. Our findings suggest that mitochondrial dysfunction and impaired responses to oxidative stress are early manifestations of PGRN loss, and offer insights into the molecular mechanisms driving neurodegeneration caused by PGRN deficiency. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=115 SRC="FIGDIR/small/691344v1_ufig1.gif" ALT="Figure 1"> View larger version (18K): org.highwire.dtl.DTLVardef@c477e5org.highwire.dtl.DTLVardef@9b61eforg.highwire.dtl.DTLVardef@13aadeborg.highwire.dtl.DTLVardef@1702929_HPS_FORMAT_FIGEXP M_FIG O_FLOATNOGraphical AbstractC_FLOATNO Proposed molecular mechanisms that lead to ferroptosis of PGRN KO cells. Created with BioRender.com. C_FIG

neuroscience↗

bioRxiv2025

Domain-specific decoupling of co-chaperone and ligase functions in STUB1 underlies biochemical and clinical heterogeneity in SCA48

AO_SCPLOWBSTRACTC_SCPLOWThe carboxyl terminus of HSC70-interacting protein (CHIP, encoded by STUB1) integrates co-chaperone and E3 ubiquitin ligase activities to maintain proteostasis. Heterozygous STUB1 mutations cause the dominant cerebellar ataxia SCA48 through incompletely understood mechanisms. We characterized 13 SCA48-associated variants in the TPR and U-box domains using recombinant protein and cellular assays. TPR mutations retained intrinsic ligase activity but lost HSC70 binding, substrate ubiquitination efficiency, and protein stability. Conversely, U-box mutations abolished ligase function, induced aberrant high-molecular-weight oligomerization, and frequently elevated steady-state CHIP levels while only partially impairing co-chaperone activity. Many variants exhibited temperature-sensitive defects and stress-induced nuclear mislocalization. Principal component analysis revealed robust domain-specific biochemical clustering. RNA-seq following STUB1 knockdown demonstrated preserved HSF1-dependent transactivation but a loss of CHIP-dependent amplification of ubiquitination, chaperone, and transcriptional pathways under heat stress. Meta-analysis of 87 SCA48 patients linked TPR-like biochemical profiles to upper motor neuron involvement and U-box profiles to prominent dysarthria. Collectively, SCA48 mutations decouple CHIPs dual functions in a domain-dependent manner, exerting dominant-negative or gain-of-toxic effects that drive the observed clinical heterogeneity. These findings establish a direct biochemical-clinical correlation in SCA48 and provide a framework for domain-targeted therapeutic strategies exploiting residual ligase or chaperone activity.

neuroscience↗

bioRxiv2025

Knocking out two polyphenol oxidase genes significantly improves recombinant protein purification in Nicotiana benthamiana

Efficient purification remains one of the major bottlenecks in the development of plant-based systems for recombinant protein production. The complex metabolites, particularly polyphenols, which usually cause recombinant protein aggregation during purification. In this study, we identified two key polyphenol oxidase genes, PPOa and PPOb from N.benthamiana as responsible for these effects. Using CRISPR/Cas9, we generated two ppoa;ppob double knockout lines that significantly improved the purification of functional proteins like SARS-CoV-2 Spike trimer and influenza HA trimer. These lines showed reduced polyphenol-protein interactions, minimized aggregation, and higher purification yields. Our work establishes a clean, high-efficiency N. benthamiana chassis for scalable recombinant protein production.

synthetic biology↗

bioRxiv2025

Leveraging BRG1 Driven Ferroptosis Resistance to Overcome Treatment Resistance

Resistance to Brutons tyrosine kinase inhibitors (BTKi) remains a major therapeutic challenge in B-cell malignancies, limiting treatment durability. Here, we identify ferroptosis suppression as a central mechanism of BTKi resistance in mantle cell lymphoma (MCL). Aberrant BRG1 activity protects cells from BTKi-induced ferroptosis by restricting reactive oxygen species (ROS) and labile iron. Mechanistically, BRG1 promotes resistance through both BTK-dependent survival signaling and a BTK-independent transcriptional program. The latter is mediated by BRG1-driven induction of MEF2B, which upregulates NDUFA4L2 to inhibit mitochondrial respiration, thereby blocking mitochondria-dependent ferroptosis. Pharmacologic inhibition of BRG1 disrupts these programs, restoring ferroptotic sensitivity and synergizing with BTKi across resistant MCL models. Together, these findings establish BRG1 as a central regulator of therapy resistance and provide a rationale for co-targeting BRG1 and BTK as a therapeutic strategy for B-cell malignancies.

cancer biology↗

bioRxiv2025

Protective mechanisms against Alzheimer's Disease in APOE3-Christchurch homozygous astrocytes

The APOE3-Christchurch (APOE3-Ch) variant has been linked to reduced Alzheimers Disease (AD) risk, but its protective mechanisms remain unclear. This study explores the neuroprotective phenotype of APOE3-Ch astrocytes, focusing on lipid metabolism and tau processing. APOE3-Ch astrocytes demonstrate enhanced tau oligomer uptake via HSPG- and LRP1-mediated pathways, facilitated by elevated HSPG expression, and achieve superior tau degradation through lysosomal pathways and proteasomal pathways, in contrast to wild-type astrocytes, which primarily use proteasomal mechanisms. Transcriptomic analysis reveals upregulation of genes involved in endocytosis and cell projection assembly, explaining enhanced tau uptake and clearance in APOE3-Ch astrocytes. Lipidomic profiling identifies reduced levels of pathological lipids such as ceramides and gamma-linolenic acid (GLA), potentially mitigating neuroinflammation. These findings provide insight into the protective mechanisms of APOE3-Ch astrocytes and underscore their potential as therapeutic targets for tauopathy and neurodegeneration in AD. TeaserAPOE3-Christchurch astrocytes enhance tau clearance and mitigate neurotoxic lipid accumulation, unveiling protective mechanisms against Alzheimers.

neuroscience↗

bioRxiv2024

Type I interferon signaling enhances kainic acid-induced seizure severity

Epilepsy is a chronic neurological disorder characterized by recurrent seizures, yet the role and mechanisms of type I interferon (IFN) signaling in seizure conditions remain elusive. In this study, we demonstrate that type I IFN signaling exacerbates seizure phenotypes in a kainic acid-induced seizure mouse model. We found that the absence of type I IFN signaling in Ifnar1-/- mice led to decreased neuronal excitability and microglial activation in response to kainic acid stimulation. Conversely, intracerebroventricular injection of IFN-{beta} heightened the severity of kainic acid-induced seizures. In vitro calcium imaging revealed that IFN-{beta} treatment amplified both basal and kainic acid-induced neuronal excitability, though no significant difference was observed in basal neuronal excitability between wild-type and Ifnar1-/- neurons. Furthermore, Ifnar1-/- mice exhibited reduced mTOR activation in the brain following kainic acid administration. Consistent with this finding, IFN-{beta} treatment induced mTOR activation, as indicated by S6 phosphorylation in in vitro mixed glial cultures. Taken together, these results demonstrate the critical role of type I IFN signaling in seizure pathogenesis and suggest that targeting type I IFNs could be a promising therapeutic strategy for reducing seizure severity and mitigating epilepsy.

neuroscience↗

bioRxiv2024

Differential Responses of Lung and Intestinal Microbiota to SARS-CoV-2 Infection: A Comparative Study of the Wuhan and Omicron Strains in K18-hACE2 tg Mice

The COVID-19 pandemic, caused by SARS-CoV-2, has led to the emergence of viral variants with distinct characteristics. We investigated the differential effects of the original Wuhan strain and the emergent Omicron variant of SARS-CoV-2 using a K18-hACE2 transgenic mouse model. We compared the mortality rates, viral loads, and histopathological changes in lung and tracheal tissues, as well as alterations in the lung and intestinal microbiota following infection. We observed significant differences in disease severity, with the Wuhan strain causing higher mortality and more severe lung damage than the Omicron variant. Furthermore, microbiome analyses revealed distinct shifts in microbiota associated with infection by each variant, suggesting that microbiome-related mechanisms might influence disease outcomes. This comprehensive comparison enhances our understanding of COVID-19 pathogenesis and highlights the importance of microbiome dynamics in viral infections, providing insights for future therapeutic and preventive strategies. ImportanceUnderstanding the differential impacts of SARS-CoV-2 variants is crucial for effective public health response and treatment development. This study provides insights into the pathogenesis of the original Wuhan strain and the Omicron variant of SARS-CoV-2, revealing significant differences in host mortality, viral load, and lung pathology. The use of the K18-hACE2 transgenic mouse model enables detailed examination of these differences in a controlled setting. Furthermore, this study highlights the importance of the microbiome in modulating disease severity and host responses to viral infections. By uncovering distinct microbial shifts associated with infection by different SARS-CoV-2 variants, this study suggests potential microbiome-related mechanisms that might be targeted to mitigate disease outcomes.

microbiology↗

bioRxiv2023

Decoding spatial organization maps and context-specific landscapes of breast cancer and its microenvironment via high-resolution spatial transcriptomic analysis

Single-cell RNA transcriptomics has revealed the intricate heterogeneity of both tumors and their microenvironment. However, a notable limitation is its inability to retain spatial context, a crucial aspect of understanding cell identity and function. In this study, we employed imaging-based single-cell spatial transcriptomics to elucidate the tumor and immunological landscapes of two breast cancer samples. By resolving over 400 000 cells per slide, we demonstrated that transcriptional differences lead to structural disparities within and between tumors. Additionally, we observed that the composition of the tumor microenvironment varies depending on its spatial location. Notably, we detected immune cell gradients transitioning from the tumor periphery to its core regions and from tertiary lymphoid structure to immune inflamed regions, in alignment with the specific function of each cell type. This finding facilitated a more precise classification of the tumor immune microenvironment. This study provides a comprehensive dataset for breast cancer researchers and underscores the significance of spatial context in understanding the multifaceted heterogeneity of cancer and its environment.

cancer biology↗

bioRxiv2023

Histone demethylase KDM2A is a selective vulnerability of cancers relying on alternative telomere maintenance

Telomere length maintenance is essential for cellular immortalization and tumorigenesis. 5% - 10% of human cancers rely on a recombination-based mechanism termed alternative lengthening of telomeres (ALT) to sustain their replicative immortality, yet there are currently no targeted therapies. Through CRISPR/Cas9-based genetic screens in an ALT-immortalized isogenic cellular model, here we identify histone lysine demethylase KDM2A as a molecular vulnerability selectively for cells contingent on ALT-dependent telomere maintenance. Mechanistically, we demonstrate that KDM2A is required for dissolution of the ALT-specific telomere clusters following homology-directed telomere DNA synthesis. We show that KDM2A promotes de-clustering of ALT multitelomeres through facilitating isopeptidase SENP6-mediated SUMO deconjugation at telomeres. Inactivation of KDM2A or SENP6 impairs post-recombination telomere de-SUMOylation and thus dissolution of ALT telomere clusters, leading to gross chromosome missegregation and mitotic cell death. These findings together establish KDM2A as a selective molecular vulnerability and a promising drug target for ALT-dependent cancers.

cancer biology↗

bioRxiv2022

SnRK1 inhibits anthocyanin biosynthesis through both transcriptional regulation and direct phosphorylation and dissociation of the MYB/bHLH/TTG1 MBW complex.

Plants have evolved an extensive specialized secondary metabolism. The colorful flavonoid anthocyanins, for example, not only stimulate flower pollination and seed dispersal but also protect different tissues against high light, UV- and oxidative stress. Their biosynthesis is highly regulated by environmental and developmental cues and induced by high sucrose levels. Expression of the biosynthetic enzymes involved is controlled by a transcriptional MBW complex, comprising (R2R3) MYB- and bHLH-type transcription factors (TF) and the WD40 repeat protein TTG1. Anthocyanin biosynthesis is obviously useful but also carbon- and energy-intensive and non-vital. Consistently, the SnRK1 protein kinase, a metabolic sensor activated in carbon- and energy-depleting stress conditions, represses anthocyanin biosynthesis. Here we show that Arabidopsis SnRK1 represses MBW complex activity both at the transcriptional and post-translational level. In addition to repressing expression of the key transcription factor MYB75/PAP1, SnRK1 activity triggers MBW complex dissociation, associated with loss of target promoter binding, MYB75 protein degradation and nuclear export of TTG1. We also provide evidence for direct interaction with and phosphorylation of multiple MBW complex proteins. These results indicate that repression of expensive anthocyanin biosynthesis is an important strategy to save energy and redirect carbon flow to more essential processes for survival in metabolic stress conditions.

plant biology↗

bioRxiv2022

Exploration of mechanisms of drug resistance by polyaneuploid cancer cells in a microfluidic device and patient tissues

Chemoresistance is a major cause of treatment failure in many cancers. However, the life cycle of cancer cells as they respond to and survive environmental and therapeutic stress is understudied. In this study, we utilized a microfluidic device to induce the development of doxorubicin-resistant (DOXR) cells from triple negative breast cancer (TNBC) cells within 11 days by generating gradients of DOX and medium. In vivo chemoresistant xenograft models, an unbiased genome-wide transcriptome analysis, and a patient data/tissue analysis all showed that chemoresistance arose from failed epigenetic control of the nuclear protein-1 (NUPR1)/histone deacetylase 11 (HDAC11) axis, and high Nupr1 expression correlated with poor clinical outcomes. These results suggest that the chip can rapidly induce resistant cells that increase tumor heterogeneity and chemoresistance, highlighting the need for further studies on the epigenetic control of the NUPR1/HDAC11 axis in TNBC.

cancer biology↗

bioRxiv2022

The chromosome-level genome of Water-Wisteria establishes an ecological plant model and provides insight into the molecular mechanisms underlying heterophylly in amphibious plants

Heterophylly is a phenomenon in which an individual plant dramatically changes its leaf shape in response to the surrounding environment. Hygrophila difformis (Acanthaceae), also known as water wisteria, has recently emerged as a model plant to study heterophylly because of its striking leaf shape variation in response to various ecological factors. Under submerged conditions, H. difformis develops complex leaves and in terrestrial conditions it develops simple leaves. Here, we sequenced and assembled the chromosome-level genome of triploid H. difformis (scaffold N50: 60.43 Mb, genome size: 871.92 Mb), which reveals 36,099 predicted protein-coding genes distributed over 15 pseudochromosomes. H. difformis diverged from its relatives during the Oligocene climate-change period and expanded the gene families related to its amphibious lifestyle. Genes involved in environmental stimuli, leaf development, and other pathways are differentially expressed in submerged and terrestrial conditions, possibly modulating morphological and physiological acclimation to changing environments. We confirmed that auxin plays a role in the heterophylly of H. difformis. Finally, we discovered candidate genes that respond to different environmental conditions and elucidated the role of LATE MERISTEM IDENTITY 1 (LMI1) in heterophylly. Our study establishes H. difformis as a model for studying the interconnections between ecological adaptation and plant morphological features.

plant biology↗

bioRxiv2022

SARS-CoV-2 Infection of Microglia Elicits Pro-inflammatory Activation and Apoptotic Cell Death

Accumulating evidence suggests that severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection causes various neurological symptoms in coronavirus disease 2019 (COVID-19) patients. The most dominant immune cells in the brain are microglia. Yet, the relationship between neurological manifestations, neuroinflammation, and host immune response of microglia to SARS-CoV-2 has not been well characterized. Here, we report that SARS-CoV-2 can directly infect human microglia, eliciting M1-like pro-inflammatory responses, followed by cytopathic effects. Specifically, SARS-CoV-2 infected human microglial clone 3 (HMC3), leading to inflammatory activation and cell death. RNA-seq analysis also revealed that ER stress and immune responses were induced in the early and apoptotic processes in the late phase of viral infection. SARS-CoV-2-infected HMC3 showed the M1 phenotype and produced pro-inflammatory cytokines such as interleukin (IL)-1{beta}, IL-6, and tumour necrosis factor (TNF-), but not the anti-inflammatory cytokine IL-10. After this pro-inflammatory activation, SARS-CoV-2 infection promoted both intrinsic and extrinsic death receptor-mediated apoptosis in HMC3. Using K18-hACE2 transgenic mice, murine microglia were also infected by intranasal inoculation of SARS-CoV-2. This infection induced the acute production of pro-inflammatory microglial IL-6 and TNF- and provoked a chronic loss of microglia. Our findings suggest that microglia are potential mediators of SARS-CoV-2-induced neurological problems and, consequently, can be targets of therapeutic strategies against neurological diseases in COVID-19 patients. IMPORTANCERecent studies reported neurological manifestations and complications in COVID-19 patients, which are associated with neuroinflammation. As microglia are the dominant immune cells in brains, it needs to be elucidate the relationship between neuroinflammation and host immune response of microglia to SARS-CoV-2. Here, we suggest that SARS-CoV-2 can directly infect human microglia with cytopathic effect (CPE) using human microglial clone 3 (HMC3). The infected microglia were promoted to pro-inflammatory activation following apoptotic cell death. This pro-inflammatory activation was accompanied by the high production of pro-inflammatory cytokines, and led to neurotoxic-M1 phenotype polarization. In vivo, murine microglia were infected and produced pro-inflammatory cytokines and provoked a chronic loss using K18-hACE2 mice. Thus, our data present that SARS-CoV-2-infected microglia are potential mediators of neurological problems in COVID-19 patients. In addition, HMC3 cells are susceptible to SARS-CoV-2 and exhibit the CPE, which can be further used to investigate cellular and molecular mechanisms of neuroinflammation reported in COVID-19 patients.

microbiology↗

bioRxiv2021

HEAT SHOCK FACTOR BINDING PROTEIN limits meiotic crossovers by repressing HEI10 transcription

The number of meiotic crossovers is tightly controlled and most depend on pro-crossover ZMM proteins, such as the E3 ligase HEI10. Despite the importance of HEI10 dosage for crossover formation, how HEI10 transcription is controlled remains unexplored. In a forward genetic screen using a sensitive fluorescent seed crossover reporter in Arabidopsis thaliana we identify heat shock factor binding protein (HSBP) as a repressor of HEI10 transcription and crossover numbers. Using genome-wide crossover mapping and cytogenetics, we show that hsbp mutations or meiotic HSBP knockdowns increase ZMM-dependent crossovers towards the telomeres, mirroring the effects of HEI10 overexpression. Through RNA sequencing, DNA methylome and chromatin immunoprecipitation analysis, we reveal that HSBP directly represses HEI10 transcription by binding with heat shock factors (HSFs) at the HEI10 promoter and maintaining DNA methylation over the HEI10 5' untranslated region. Our findings provide insights into how the temperature response regulator HSBP restricts meiotic HEI10 transcription and crossover number by attenuating HSF activity.

plant biology↗