Biology subjects

Ji, P.

Publications and source records attributed to Ji, P..

At least 19 recordsLinked to original sources

bioRxiv2026

Ultrastructural analysis of engineered rice lines reveals ferulate cross-linking as a key factor mediating lignocellulose supramolecular assembly in grass cell walls

Within the secondary cell walls of vascular plants, cellulose, hemicelluloses, and lignin associate via various covalent and non-covalent linkages to form an intricate supramolecular assembly. Although the chemical structures and cross-linking levels of the lignin- hemicellulose matrix exhibit substantial diversity in planta, precisely how these structural variations affect lignocellulose supramolecular assembly and macroscopic biomass properties remains largely elusive. Here, we conducted a comparative multi-scale ultrastructural analysis across engineered rice lines with targeted modifications in lignin aromatic composition and ferulate (FA)-mediated cell wall cross-linking levels. Combined solid-state nuclear magnetic resonance and wide-angle X-ray diffraction analyses revealed that depleting FA cross-linking disrupts cellulose crystalline structure and accelerates molecular mobility markedly more severely than altering the guaiacyl-to-syringyl (G/S) lignin ratio, generating a more loosened lignocellulose network. Small-angle X-ray scattering analysis further demonstrated that specific FA-depleted lines, but none of those with an altered G/S ratio, also exhibited disruptions in the nano- to mesoscale organization of cellulose microfibrils. Furthermore, FA- depleted lines generally displayed greater improvements in saccharification efficiency and more rapid thermal softening than G/S-lignin-altered lines, suggesting that disruptions in lignocellulose molecular assembly induced by FA depletion can broadly translate into macroscopic biomass properties. These findings establish a molecular basis for the pivotal role of FA cross-linking in dictating grass cell wall architecture, offering a promising structural target for advancing grass biomass utility and crop design.

plant biology↗

bioRxiv2026

Stromal Gasdermin D-mediated Pyroptosis Drives Maladaptive CD4⁺ T-cell Remodeling in Tet2-Deficient Hematopoiesis

An inflammatory bone marrow microenvironment is increasingly recognized as critical in myeloid disease evolution, yet how stromal inflammation interfaces with adaptive immunity remains poorly defined. Here, we show that stromal pyroptosis drives mutation-specific myeloid expansion by coordinating monocytic remodeling and CD4 T-cell activation. Genetic ablation of gasdermin D in the bone marrow stroma suppressed stromal pyroptosis and attenuated Tet2-deficient myeloid expansion. Tet2 deficiency skewed monocyte and macrophage differentiation toward an activated, antigen-presenting state that interacted with pyroptotic stromal cells to promote expansion of a distinct CD4 T-cell population. These cells expressed canonical T follicular helper markers (Bcl6, Cxcr5, Il21, and Cd40l) together with interferon-responsive and tissue-interaction programs, consistent with an inflammation-adapted TFH-like state. CD40L produced by these cells reinforced the expansion of Tet2-deficient monocytes and macrophages, establishing a feed-forward stromal-immune circuit. Disruption of this axis through stromal gasdermin D deficiency or CD40L blockade attenuated myeloid expansion in vivo. Consistent with these findings, patients with isolated TET2 loss-of-function mutations exhibited CD4 T-cell skewing and CD40L+ T-cell-rich tertiary lymphoid structures in the bone marrow. Together, these data identify a pyroptosis-dependent stromal-immune axis that links early myeloid inflammation to maladaptive remodeling of adaptive immunity and reveals a context-dependent therapeutic vulnerability in Tet2-deficient hematopoiesis.

cancer biology↗

bioRxiv2026

GPLD1 Regulates the Shedding of IZUMO1R to Block Polyspermy in Porcine Oocyte

Mammalian fertilization commences with the essential interaction between sperm IZUMO1 and its oocyte-surface receptor, JUNO. Following gamete fusion, JUNO is rapidly shed from the oocyte to establish a definitive membrane block to polyspermy, a pathological condition that remains a major hurdle in porcine in vitro fertilization (IVF). Despite its biological importance, the molecular networks driving JUNO cleavage has remained elusive. Here, by integrating proteomics, dual-color live-cell imaging, and functional perturbations, we identify the extended existence of JUNO and the GPI-specific phospholipase D1 (GPLD1) as the requisite enzyme mediating JUNO shedding in porcine oocytes. Targeted knockdown or pharmacological inhibition of GPLD1 stabilizes oocyte JUNO, prolongs the window of oocyte receptivity, and significantly exacerbates polyspermy, ultimately compromising embryonic developmental competence. Conversely, GPLD1 overexpression restricts redundant sperm adherence and enhances the efficiency of monospermic zygote formation and blastocyst development. Live-cell imaging reveals that fertilization triggers a transient, pulsed recruitment of GPLD1 in the oocyte, which precisely coincides with the biphasic kinetics of JUNO depletion. Our findings establish that the enzymatic cleavage of the GPI-anchor by GPLD1 is critical for JUNO release, defining a fundamental mechanism for the membrane-level block to polyspermy. This work provides a molecular framework for ensuring sperm-oocyte recognition and improving in vitro fertilization outcomes in mammals.

developmental biology↗

bioRxiv2026

Binary-SPA: A Reference-Free Method for Cell Annotation in High-Resolution Spatial Transcriptomics

Accurate cell type annotation remains a major challenge in high-resolution spatial transcriptomics analysis. Current approaches primarily rely on label transfer from single-cell RNA sequencing (scRNA-seq) reference datasets or marker-based annotation of transcriptionally defined clusters. While these methods are widely used, they have critical limitations. Label transfer approaches depend on the availability of a well-matched scRNA-seq reference. Marker-based annotation methods often suffer from accuracy and limited coverage. To address these challenges, we developed Binary-SPA, a computational framework for cell-type annotation of high-resolution spatial transcriptomics data. Binary-SPA performs annotation in two stages. First, a binary classification step identifies high-confidence cells using predefined marker sets. These confidently annotated cells are then used as an internal reference for anchor-based label transfer in the second stage. Binary-SPA outperforms conventional marker-based annotation approaches and existing label transfer methods across multiple high-resolution spatial transcriptomics platforms, preservation methods, and tissue types. While label transfer methods achieve high accuracy only when same-tissue scRNA-seq references are available, and decline substantially when relying on independent datasets, Binary-SPA matches this performance with 100% annotation coverage while eliminating the need for external reference data entirely. Binary-SPA demonstrates robust performance even in challenging specimens such as bone marrow biopsies, and validation against matched COMET protein expression data confirmed strong concordance between transcriptomic- and protein-based cell identities. Binary-SPA thus provides a robust, reference-free solution for spatial transcriptomics annotation with broad applicability to research and clinical specimens.

genomics↗

bioRxiv2025

Computational design of metalloproteases

Although significant progress has been made in creating de novo metalloenzymes that hydrolyze activated esters, the energetically demanding cleavage of amide bonds has remained a major challenge for enzyme design: amide bonds are significantly more stable than ester bonds, the amine leaving groups in proteins are not activated, and peptide substrates are flexible making them difficult to bind precisely. Here, we report the de novo design of zinc proteases from minimal catalytic motifs using RoseTTAFold Diffusion 2 for Molecular Interfaces, optimized for both enzyme and protein-protein interaction design. Of 135 computational designs experimentally tested, 36% had activity and cleaved precisely at the intended site. The most active design accelerates peptide bond hydrolysis by more than 10^8-fold relative to the uncatalyzed reaction, and by over 10^10-fold following the introduction of four point mutations that enhanced active-site preorganization4. Building on these capabilities, we designed metalloproteases that specifically cleave human TDP-43, the amyloid-{beta} peptide, and serum amyloid A with rate accelerations up to 9.2x10^8-fold over background. We illustrate the potential of our approach for bio-orthogonal control over cell state by generating caged cytokines and caged receptor antagonists that are selectively unmasked by our designed proteases. These results demonstrate that de novo enzyme design has advanced well beyond model reactions with activated substrates and open the door to design of proficient metallohydrolases for a wide range of applications in medicine and bioremediation.

biochemistry↗

bioRxiv2025

Central nervous system atlas of larval zebrafish constructed using the morphology of single excitatory and inhibitory neurons

Single-neuron morphology mapping is fundamental for deciphering brain architecture and function, yet in vertebrates it remains limited in spatial coverage and cell-type information. Here we present a nervous system-wide single-neuron morphology atlas of larval zebrafish with annotated excitatory/inhibitory identity and dendrite-axon polarity. The atlas comprises >20,000 reconstructed neurons from >13,400 animals, spanning the central and peripheral nervous system and representing [~]24.5% of the total excitatory and inhibitory neurons in the brain, all integrated into a common physical space with neuroanatomical parcellations. We define >500 excitatory and inhibitory neuronal morphotypes and construct putative inter-cell-type and interregional connectomes. Projection and morphotype analyses reveal distinct laterality and directionality biases and modular innervation patterns in excitatory and inhibitory neurons, while network analyses uncover fundamental connectivity motifs, hubs, and sensorimotor pathways. Accessible through custom-built interactive platform ZExplorer, this atlas provides a foundational resource for multimodal data integration, circuit analysis, computational modeling, and hypothesis-driven research.

neuroscience↗

bioRxiv2025

Stacked mutations disrupting syringyl and p-coumaroylated lignin biosynthesis in rice result in lignin dominated by guaiacyl units: insights into grass-specific lignin monomer biosynthesis and polymerization mechanisms

O_LIThe aromatic composition of lignin significantly impacts the usability of lignocellulosic biomass. In eudicots, transgenic and mutant lines with elevated guaiacyl (G) or syringyl (S) lignin units have been successfully generated by manipulating the expression level of CONIFERALDEHYDE 5-HYDROXYLASE (CAld5H). However, this bioengineering approach has proven less effective in grasses, implicating the potential existence of a grass-specific alternative pathway for S lignin biosynthesis. C_LIO_LIThrough characterization of genome-edited rice mutants, we demonstrated that S lignin in rice can be virtually eliminated by disrupting genes encoding CAld5H along with p- COUMAROYL-COENZYME A:MONOLIGNOL TRANSFERASE (PMT), a grass-specific enzyme essential for the biosynthesis of monolignol p-coumarate conjugates. In contrast, individual mutations in either CAld5H or PMT genes resulted in incomplete elimination of S lignin. These findings provide strong evidence that rice possesses a CAld5H-independent pathway leading to the grass-specific monolignol p-coumarate conjugates. C_LIO_LIIn-depth structural characterizations of G-dominated lignins from rice and Arabidopsis mutants, natural gymnosperm pine, and G-type synthetic lignin revealed pronounced effects of lineage-dependent cell wall environments on the linkage patterns and molecular weight distributions of the resulting lignin polymers. C_LIO_LIOverall, our findings highlight previously overlooked lineage-specific lignin monomer biosynthesis and polymerization patterns in grasses. C_LI

plant biology↗

bioRxiv2025

Shear Stress Conditioning Promotes a Pro-Inflammatory Response in Porcine Endocardial Endothelial Cells

PURPOSEDiscrete subaortic stenosis (DSS) is a congenital heart disease characterized by a narrowing of the passage below the aortic valve in the left ventricular outflow tract (LVOT) [1]. While endocardial endothelial cells (EECs) are known to play a role in DSS, the response of these cells to shear stress is not known. In this study, we hypothesize that the response of EECs to shear stress in the LVOT is a mediator of DSS. METHODSTo test this hypothesis, we conditioned porcine EECs to controlled shear stress regimes using cone and plate bioreactors. Subsequently, we quantified the concentration of proinflammatory cytokine in the conditioned media using the Luminex assay. Bulk-RNA sequencing was used to quantify changes in the genotype of the shear stress conditioned EECs. RESULTSThe expression of CD31 was knocked down and subsequently, the changes in release of shear stress induced proinflammatory cytokines released by EECs quantified using the Luminex assay. The results of these studies show that the inflammatory cytokines were highly selected in the conditioning medium, and under bioreactor treatment the cell activated the PI3K-AKT and TNF-a signaling, which also triggered the other immune cell responses though Th1, Th2 and Th17 cell differentiation pathways. Furthermore, CD31 was identified as a mediator of the pro-inflammatory response of shear stress conditioned EECs. CONCLUSIONSThe studies provide a clear link between shear stress, and the subsequent proinflammatory response of EECs as a mediator of DSS.

bioengineering↗

bioRxiv2025

Shear Stress Modulates Inflammatory Responses in Porcine Endothelial Cells Contributing to the Fibrotic Response of Porcine Cardiac Fibroblasts

This study is focused on discrete subaortic stenosis (DSS) which is a congenital heart disease resulting in the formation of fibrotic tissue in the left ventricular outflow track of pediatric patients [1]. The pathogenesis of the molecular mechanism resulting in the formation of the fibrotic tissue remains unknown and is the focus of this study. We hypothesized the cytokine released in response to wall shear stress act on the fibroblasts to promote the formation of the fibrotic membrane and subsequently, DSS. To test this study hypothesis, porcine endocardial endothelial cells were cultured within cone and plate bioreactors, designed to replicate the wall shear stress observed in the left ventricular outflow track of DSS patients. Conditioned media was collected as a function of shear stress magnitude and used to condition porcine cardiac fibroblasts. We used an extensive set of end-point metrics to characterize fibroblast phenotype to include bulk-RNA sequencing, RT-qPCR, cell viability and immunofluorescence. The results of this study demonstrate that shear stress-conditioned media from porcine EEC releases a defined cocktail of cytokines that provide the trigger to program the fibrotic response during DSS. These results provide specific molecular targets that can be developed into a therapeutic strategy for patients with DSS and provide a solution to an otherwise challenging disease to manage.

bioengineering↗

bioRxiv2024

DDX41 dissolves G-quadruplexes to maintain erythroid genome integrity and prevent cGAS-mediated cell death

Deleterious germline DDX41 variants constitute the most common inherited predisposition disorder linked to myeloid neoplasms (MNs). The role of DDX41 in hematopoiesis and how its germline and somatic mutations contribute to MNs remain unclear. Here we show that DDX41 is essential for erythropoiesis but dispensable for the development of other hematopoietic lineages. Using stage-specific Cre models for erythropoiesis, we reveal that Ddx41 knockout in early erythropoiesis is embryonically lethal, while knockout in late-stage terminal erythropoiesis allows mice to survive with normal blood counts. DDX41 deficiency induces a significant upregulation of G-quadruplexes (G4), noncanonical DNA structures that tend to accumulate in the early stages of erythroid precursors. We show that DDX41 co-localizes with G4 on the erythroid genome. DDX41 directly binds to and dissolves G4, which is significantly compromised in MN-associated DDX41 mutants. Accumulation of G4 by DDX41 deficiency induces erythroid genome instability, defects in ribosomal biogenesis, and upregulation of p53. However, p53 deficiency does not rescue the embryonic death of Ddx41 hematopoietic-specific knockout mice. In parallel, genome instability also activates the cGas-Sting pathway, which is detrimental to survival since cGas-deficient and hematopoietic-specific Ddx41 knockout mice are viable without detectable hematologic phenotypes, although these mice continue to show erythroid ribosomal defects and upregulation of p53. These findings are further supported by data from a DDX41 mutated MN patient and human iPSC-derived bone marrow organoids. Our study establishes DDX41 as a G4 dissolver, essential for erythroid genome stability and suppressing the cGAS-STING pathway.

cancer biology↗

bioRxiv2024

Insights into the Molecular Mechanism of Pulmonary Vein Stenosis in Pediatric Patients

BackgroundPediatric pulmonary vein stenosis (PVS) is associated with substantial morbidity and mortality for the subset of patients with recurrent or progressive disease. The molecular mechanisms underlying the development and trajectory of PVS remain unclear. This study characterizes the transcriptome of clinical and phenotypic subtypes of PVS. MethodsBulk RNA sequencing analysis was performed on human pulmonary vein tissue samples obtained from surgical interventions for pediatric patients with PVS. Transcriptomic profiles were compared for primary versus post-repair PVS as well as aggressive versus non-aggressive clinical phenotypes. Principal component analysis was performed, the differential gene expression quantified, and pathway analysis conducted based on gene ontology, KEGG and Reactome. ResultsWhen comparing AggPPVS vs NonAggPPVS, differences were noted in the genes associated in extracellular matrix regulation and PIEZO1, a mechanosensitive receptor present in endothelial cells. In addition, there were notable changes in cardiac muscle contractility, calcium handling, respiratory and energy metabolism. These results point to a potential mechanism for aggressive PPVS phenotype, due to an overexpression of PIEOZ1 in response to elevated shear stress, subsequent activation of intracellular signaling pathways and leading to reduced contractility and intracellular calcium transients with cardiomyocytes. ConclusionsThe result of this study suggests that aggressive PPVS phenotype is caused by an increase in PIEZO1 expression and subsequent changes in extracellular matrix production, heart muscle contractility and changes in calcium transients within cardiomyocytes. These results provide a potential target for therapeutic invention for primary PPVS by inhibiting the activity of PIEZO1. This could potentially reduce morbidity in this patient population.

genomics↗

bioRxiv2024

Essential Yet Dispensable: The Role of CINNAMATE 4-HYDROXYLASE in Rice Cell Wall Lignification

A comprehensive understanding of the intricate lignin biosynthesis in grasses could contribute to enhancing our ability to utilize grass biomass. CINNAMATE 4-HYDROXYLASE (C4H), in conjunction with PHENYLALANINE AMMONIA-LYASE (PAL), initiates the entry of phenylalanine into the cinnamate/monolignol pathway, leading to the production of diverse phenylpropanoids, including lignin monomers. Despite extensive research on C4H in eudicots, genetic studies of C4H in grasses remain considerably limited. Notably, the role of C4H in the presence of PHENYLALANINE/TYROSINE AMMONIA-LYASE (PTAL), a grass-specific ammonia-lyase that can bypass the conserved PAL-C4H pathway by recruiting tyrosine into the cinnamate/monolignol pathway, remains unclear. To address this gap, a set of genome-edited rice mutants harboring knockout mutations in rice C4H genes were generated and subjected to the analysis of growth phenotype and cell wall chemotype, alongside isotopic feeding and chemical inhibitor assays to test the contributions of the PAL-C4H and PTAL pathways. The phenotype and chemotype characterizations of C4H-knockout rice mutants demonstrated that class I (OsC4H1/CYP73A38) and class II (OsC4H2a/CYP73A39 and OsC4H2b/CYP73A40) C4Hs cooperatively contribute to lignin biosynthesis in rice. Nevertheless, the impacts of C4H-deficiency on plant development and lignin formation in rice appeared to be less prominent compared to those reported in eudicots. The 13C-labeled phenylalanine and tyrosine feeding experiments demonstrated that even with the phenylalanine-derived PAL-C4H pathway completely blocked, the C4H-knockout rice can still produce significant levels of lignin and maintain sound cell walls by utilizing the tyrosine-derived PTAL pathway. Overall, this study demonstrates the essential but dispensable role of C4H in grass cell wall lignification.

plant biology↗

bioRxiv2024

Development of a Novel Method to Fabricate Highly Functional Human Purkinje Networks

BACKGROUNDIn this study, we present a method to bioengineer functional Purkinje networks using recent advances in laser-based bioprinting. METHODSA custom bioink as formulated using optimized concentrations of polyethylene glycol diacrylate (PEGDA), gelatin methacryloyl (GELMA), lithium phenyl-2,4,6-trimethylbenzoylphosphinate (LAP), and tartrazine. A standard triangle language (STL) model of Purkinje networks was developed based on the mammalian Purkinje network mapped out using India ink staining. A commercial bioprinter, the Lumen X, from CellInk, was used to bioprint Purkinje networks. The biocompatibility of the bioprinted Purkinje networks was tested using iPSCs from healthy donors. Negative molds of the Purkinje networks were designed to simulate interaction between Purkinje cells and adjacent cardiomyocytes using different degrees of overlap between the two cell types. The negative molds were also shown to be biocompatible, based on the culture of iPSCs derived from healthy donors. RESULTSWe were able to successfully bioprint over 100 Purkinje networks and demonstrate biocompatibility with iPSCs for up to 7 days. Three different configurations of the negative molds were designed and fabricated and all three shown to be biocompatible with iPSCs for up to 7 days. A co-culture system was developed by placing the Purkinje networks in proximity to the negative molds for all three configurations designed. CONCLUSIONOur results demonstrate the ability to bioprint Purkinje networks and molds and provide an in vitro system to study the functional interaction between Purkinje cells and adjacent cardiomyocytes.

bioengineering↗

bioRxiv2024

Morroniside promotes skin wound re-epithelialization by facilitating epidermal stem cell proliferation through GLP-1R-mediated upregulation of β-catenin expression

Epidermal stem cells (EpSCs) play a vital role in skin wound healing through re-epithelialization. Identifying chemicals that can promote EpSC proliferation is helpful for treating skin wounds. This study investigates the effect of morroniside on cutaneous wound healing in mice and explores the underlying mechanisms. Application of 10-50 g/mL of morroniside to the skin wound promotes wound healing in mice. In vitro studies demonstrate that morroniside stimulates the proliferation of mouse and human EpSCs in a time- and dose-dependent manner. Mechanistic studies reveal that morroniside promotes the proliferation of EpSCs by facilitating the cell cycle transition from the G1 to S phase. Morroniside increases the expression of {beta}-catenin via the glucagon-like peptide-1 receptor (GLP-1R)-mediated PKA, PKA/PI3K/AKT and PKA/ERK signalling pathways, resulting in the increase of cyclin D1 and cyclin E1 expression, either directly or by upregulating c-Myc expression. This process ultimately leads to EpSC proliferation. Administration of morroniside to mouse skin wounds increases the phosphorylation of AKT and ERK, the expression of {beta}-catenin, c-Myc, cyclin D1, and cyclin E1, as well as the proliferation of EpSCs, in periwound skin tissue, and accelerates wound re-epithelialization. These effects of morroniside are mediated by the GLP-1R. Overall, these results indicate that morroniside promotes skin wound healing by stimulating the proliferation of EpSCs via increasing {beta}-catenin expression and subsequent upregulation of c-Myc, cyclin D1, and cyclin E1 expression through GLP-1R signalling pathways. Morroniside has clinical potential for treating skin wounds.

pharmacology and toxicology↗

bioRxiv2023

Regulation of the Drosophila transcriptome by Pumilio and CCR4-NOT deadenylase

The sequence-specific RNA-binding protein Pumilio controls development of Drosophila; however, the network of mRNAs that it regulates remains incompletely characterized. In this study, we utilize knockdown and knockout approaches coupled with RNA-Seq to measure the impact of Pumilio on the transcriptome of Drosophila cells. We also used an improved RNA co-immunoprecipitation method to identify Pumilio bound mRNAs in Drosophila embryos. Integration of these datasets with the content of Pumilio binding motifs across the transcriptome revealed novel direct Pumilio target genes involved in neural, muscle, wing, and germ cell development, and cellular proliferation. These genes include components of Wnt, TGF-beta, MAPK/ERK, and Notch signaling pathways, DNA replication, and lipid metabolism. Additionally, we identified the mRNAs regulated by the CCR4-NOT deadenylase complex, a key factor in Pumilio-mediated repression, and observed concordant regulation of Pumilio:CCR4-NOT target mRNAs. Computational modeling revealed that Pumilio binding, binding site number, density, and sequence context are important determinants of regulation. Moreover, the content of optimal synonymous codons in target mRNAs exhibits a striking functional relationship to Pumilio and CCR4-NOT regulation, indicating that the inherent translation efficiency and stability of the mRNA modulates their response to these trans-acting regulatory factors. Together, the results of this work provide new insights into the Pumilio regulatory network and mechanisms, and the parameters that influence the efficacy of Pumilio-mediated regulation.

molecular biology↗

bioRxiv2023

The Neonatal Gyrencephalic Cortex Maintains Regionally Distinct Streams of Neuroblasts

Neurodevelopmental mechanisms have evolved to support the formation of diverse brain structures, such as in humans, during the perinatal period. Here, we demonstrate that neonatal gyrencephalic brains harbor an expanded subventricular zone, termed the Arc, defined by tiered arrangement of doublecortin (DCX)-expressing neuroblasts and vascular enrichment at the ventricular wall. The Arc is the origin of dorsal and ventral populations of migratory neuroblasts that target multiple regions involved in higher cognitive functions. Arc-derived migratory streams, primarily from the caudal ganglionic eminence, are composed of diverse neuronal subtypes with distinct spatial and migratory-receptor profiles. Our findings indicate the Arc is a structure present in phylogenetically divergent species that supports the expansion of postnatal neuronal migration, contributing to a protracted formation of cortical circuits in gyrencephalic brains. One-Sentence SummaryThe ventricular cytoarchitecture of gyrencephalic brains supports an ongoing supply of migratory neurons to the neonatal cortex.

neuroscience↗

bioRxiv2023

Angiopoietin-like 4 promotes the proliferation and migration of epidermal stem cells and contributes to the re-epithelialization of cutaneous wounds

Proliferation and migration of epidermal stem cells (EpSCs) are essential for epithelialization during skin wound healing. Angiopoietin-like 4 (ANGPTL4) has been reported to play an important role in wound healing, but the mechanisms involved are not fully understood. Here we investigate the contribution of ANGPTL4 to full-thickness wound re-epithelialization and the underlying mechanisms using Angptl4 knockout mice. Immunohistochemical staining reveals that ANGPTL4 is significantly upregulated in the basal layer cells of the epidermis around the wound during cutaneous wound healing. ANGPTL4 deficiency impairs wound healing. H & E staining shows that ANGPTL4 deficiency significantly reduces the thickness, length and area of regenerated epidermis postwounding. Immunohistochemical staining for markers of EpSCs (6 integrin and {beta}1 integrin) and cell proliferation (PCNA) shows that the number and proliferation of EpSCs in the basal layer of the epidermis are reduced in ANGPTL4-deficient mice. In vitro studies show that ANGPTL4 deficiency impedes EpSC proliferation, causes cell cycle arrest at the G1 phase and reduced the expression of cyclins D1 and A2, which can be reversed by ANGPTL4 overexpression. ANGPTL4 deletion suppresses EpSC migration, which is also rescued by ANGPTL4 overexpression. Overexpression of ANGPTL4 in EpSCs accelerates cell proliferation and migration. Collectively, our results indicate that ANGPTL4 promotes EpSCs proliferation by upregulating cyclins D1 and A2 expression and accelerating cell cycle transition from G1 to S phase, and ANGPTL4 promotes skin wound re-epithelialization by stimulating EpSC proliferation and migration. Our study reveals a novel mechanism underlying EpSC activation and re-epithelialization during cutaneous wound healing.

cell biology↗

bioRxiv2022

Mouse NEMP1 is required for erythropoiesis, nuclear envelope openings and enucleation of erythroblasts

Nuclear Envelope Membrane Proteins (NEMP) are a conserved family of nuclear envelope proteins that reside within the inner nuclear membrane. Even though Nemp1 knockout (KO) mice are overtly normal, they display a pronounced splenomegaly. This phenotype and recent reports describing a requirement for nuclear envelope openings during erythroblasts terminal maturation led us to examine a potential role for Nemp1 in erythropoiesis. Here, we report that Nemp1 knockout (KO) mice show peripheral blood defects, anemia in neonates, ineffective erythropoiesis, splenomegaly and stress erythropoiesis. The erythroid lineage of Nemp1 KO mice is overrepresented until the pronounced apoptosis of polychromatophilic erythroblasts. We show that NEMP1 localizes to the nuclear envelope of erythroblasts and their progenitors. Mechanistically, we discovered that NEMP1 accumulates into aggregates that localize near or at the edge of nuclear envelope openings and Nemp1 deficiency leads to a marked decrease of both nuclear envelope openings and ensuing enucleation. Together, our results for the first time demonstrate that NEMP1 is essential for nuclear envelope openings and erythropoietic maturation in vivo and provide the first mouse model of defective erythropoiesis directly linked to the loss of an inner nuclear membrane protein.

cell biology↗