Biology subjects

Tripodo, C.

Publications and source records attributed to Tripodo, C..

At least 19 recordsLinked to original sources

bioRxiv2026

A genetic anemia disentangles the dual effect of chronically reduced thrombopoietin on hematopoietic stem cells and bone marrow niche

Many studies unraveled the reciprocal regulation between hematopoietic stem cells (HSC) and the bone marrow (BM) niche by using transgenic knock-out or reporter mice, often overlooking the pathophysiological relevance and the existence of compensatory mechanisms. Here, we exploit the th3 murine model of a genetic anemia, beta-thalassemia (BThal), to investigate the dual impact of chronically reduced thrombopoietin (TPO) production on HSC and megakaryocytic BM niche. Decreased systemic TPO downregulates stemness programs in HSC and impairs their commitment towards megakaryocytes (Mk). We uncover dysmegakaryopoiesis in the BM from BThal patients and mice with defective Mk maturation and reduced production of niche factors, altering the HSC-niche crosstalk. Notably, in vivo stimulation of the TPO signaling restores HSC quiescence, Mk maturation and niche support. These findings demonstrate that TPO regulates HSC through both direct and niche-mediated routes, underscoring the value of using a genetic disease model to disentangle general molecular mechanisms.

cell biology↗

bioRxiv2026

ENPP3 expressed by HER2-positive breast cancer cells is associated with good prognosis by restraining epithelial-to-mesenchymal phenotype

Background Ectonucleotide pyrophosphatase/phosphodiesterase 3 (ENPP3/CD203c) is largely studied as a marker of mast cells and basophils. By depleting extracellular ATP, it prevents excessive activation of mast cells and basophils, hence reducing inflammation and allergic reactions. Recent findings have also shown that Enpp3 can deplete cGAMP, another molecule involved in STING activation and IFN-mediated pro-inflammation. Little is still known regarding the role of Enpp3 in non-immune cells although a few reports have described its expression in healthy tissues and tumors. Methods In silico analysis were performed to investigate the expression levels and the prognostic value of Enpp3 in breast cancer, together with ovarian, prostate and colon carcinoma. ENPP3 expression was evaluated in formalin-fixed, paraffin-embedded tumor samples of breast cancer patients by immunohistochemistry, and in mouse mammary cancer cell lines by western blots. Cells were treated with EGFR ligands to stimulate the EGFR/HER2 axis. A mouse-derived mammary cancer cell line was engineered by CRISPR/Cas9 to introduce a GFP sequence under the control of the Enpp3 promoter. GFP-positive and -negative cells were sorted and analyzed by gene expression profiling to identify genes and pathways associated with Enpp3 expression. Finally, wild type and Enpp3 knockout cells were injected in the fat pad of Wsh mice, which do not have mast cells, to evaluate the growth of the tumors which were further analyzed by immunohistochemistry. Results We provide evidence that HER2-positive cells express higher levels of ENPP3 in samples of breast cancer patients. Moreover, in vitro models confirmed that HER2 expression and EGFR stimulation result in up-regulation of Enpp3. We identified pathways that can concur to Enpp3 expression and showed that in vivo the absence of Enpp3 promotes tumor growth and development of tumors with a marked epithelial-to-mesenchymal phenotype. Finally, in a small cohort of HER2-positive breast cancer patients, we found that ENPP3 expression correlates with increased relapse-free survival. Conclusions Despite its potential immunosuppressive role, our findings support the notion that ENPP3 expression is promoted by HER2 in breast cancer, and that it is endowed with a positive prognostic value.

cancer biology↗

bioRxiv2026

Spatial multi-omics identify an immunosuppressive lipid-laden macrophage niche in primary CNS lymphoma

Primary central nervous system lymphoma (PCNSL) is histologically a subtype of diffuse large B-cell lymphoma (DLBCL), sharing genetic and transcriptomic similarity, but with distinct clinical features, particularly its confinement to the CNS and higher relapse risk. The microenvironmental basis for its divergence from systemic DLBCL remains unclear. Using spatial transcriptomic approaches (Xenium/GeoMx digital spatial profiling) in a comparative study of PCNSL (n=17) and DLBCL (n=76), we found that PCNSL, unlike systemic DLBCL, is dominated by an immunosuppressive macrophage compartment enriched for cholesterol-metabolism programs. In independent cohorts of PCNSL profiled by single-cell RNA sequencing, we validated the presence of a recurrent population of lipid-laden macrophages (LLMs): TREM2/GPNMB-expressing, lipid-remodeled cells transcriptionally distinct from resident microglia and consistent with an infiltrating monocyte origin, not previously characterized in CNS lymphoma. LLMs formed immunosuppressive niches with regulatory T cells, and using Cellscape hyperplex proteomic imaging we demonstrate that LLM-Treg spatial interactions are associated with chemotherapy response. To test whether LLMs are lymphoma-driven and functionally important, we developed an immunocompetent syngeneic PCNSL mouse model, driven by Myd88L252P and Cd79b mutations with Bcl2 overexpression. Monocyte-derived macrophages in lymphoma-bearing brain regions acquired an LLM-like state, not seen in lymphoma-free brain regions or in splenic tumors driven by the same oncogenic lesions. TREM2-SYK signaling sustained this state, and SYK inhibition reversed its tumor-supportive activity ex vivo. These findings identify the LLM program as a targetable immunosuppressive myeloid state in CNS lymphoma.

cancer biology↗

bioRxiv2025

PatternExtract: A facile, scalable pipeline for point pattern generation from spatial imaging data

We present PatternExtract, an open-source pipeline that generates accurate spatial point patterns from RGB pathology images and cell coordinate data without relying on composite channels or proprietary software. Using a novel two-kernel tissue segmentation method combined with automated pixel classification in QuPath, PatternExtract precisely excludes tissue artifacts such as necrosis and blood vessels to define spatial windows. Optimized on 568 diffuse large B-cell lymphoma images and validated on an independent cohort, the pipeline enables robust spatial analyses.

bioinformatics↗

bioRxiv2025

A Chk1-Sp1-CD59 axis of the DNA damage response impedes rituximab-mediated complement-dependent cytotoxicity

The DNA damage response (DDR) is a central regulator of cancer cell fate, coordinating both pro-death and pro-survival pathways in response to genotoxic stress. Here, we reveal an unexpected role for the DDR at the cell surface, in mediating immune evasion from complement-dependent cytotoxicity (CDC), an innate immune mechanism exploited by therapeutic monoclonal antibodies (mAbs). In the context of diffuse large B-cell lymphoma (DLBCL), where the anti-CD20 mAb rituximab utilizes CDC, we show that genotoxic chemotherapy induces expression of membrane-bound complement regulatory proteins (mCRPs) CD46, CD55, and CD59, thereby reducing CDC sensitivity and compromising rituximab activity. In this setting, CD59 emerged as the dominant DDR-induced inhibitor of complement-mediated killing. A high-throughput kinase inhibitor screen identified checkpoint kinase 1 (Chk1) as a critical mediator of this response. Mechanistically, DNA damage activates Chk1, enhancing CD59 transcription via an Sp1-bound promoter. Co-immunoprecipitation mass spectrometry revealed a Chk1 dependent remodelling of Sp1-associated complexes to a transcriptionally active state with recruitment of the histone acetyltransferase KAT2A. These findings expand the role of the DDR in immune resistance at the tumor cell surface, and highlight a negative interaction between chemotherapy and monoclonal antibodies that may require sequential administration or targeting of the Chk1- Sp1-CD59 axis. SignificanceThe DNA Damage Response upregulates complement-protective proteins, extending its role in modulating immune evasion at the cell surface, with direct implications for combinations of chemotherapy and monoclonal antibodies widely used in cancer.

cancer biology↗

bioRxiv2024

B cell receptor silencing reveals the origin of high-grade B cell lymphomas with MYC and BCL2 rearrangements

The B cell receptor (BCR) is essential for mature B cell lymphomas, serving as therapeutic target. Here, we show that high-grade B cell lymphomas with MYC and BCL2 rearrangements (HGBCL-DH-BCL2) predominantly exhibit immunoglobulin heavy (IGH) chain silencing, leading to BCR shutdown. HGBCL-DH-BCL2 with undetectable IGH (IGHUND) differ from IGH-expressing counterparts for germinal center-zone gene programs, MYC expression and T cell infiltration. While IGH+ HGBCL-DH-BCL2 prefer IGM/IG-Kappa expression, IGHUND counterparts have completed IGH class-switching, favoring IG-Lambda (IGL) light chains. IGHUND HGBCL-DH-BCL2 preserve IGHV gene integrity, overcoming antigen-driven selection. IGH silencing precedes onset and shapes evolution of HGBCL-DH-BCL2 from Follicular Lymphoma (FL) or FL/HGBCL-DH-BCL2 common precursor. In FL/HGBCL-DH-BCL2 pairs and HGBCL-DH-BCL2 models, BCR silencing promoted RAG1/2-dependent IG light chain editing, causing t(8;22)(q24;q11)/IGL::MYC. IGH silencing protected HGBCL-DH-BCL2 models from killing by CD79B-targeting Polatuzumab-Vedotin. Collectively, HGBCL-DH-BCL2 primarily originate from BCR-silenced isotype-switched t(14;18)/IGH::BCL2-positive (pre)FL cells acquiring IGL::MYC translocations during IG light chain revision, with clinical implications. SignificanceThese findings link BCR silencing in isotype-switched t(14;18)+ Follicular Lymphoma cells (or their precursors) to RAG1/2 re-expression, promoting IGL::MYC translocations responsible for transformation into high-grade B cell lymphomas (HGBCL). Predominant silencing of the BCR complex in HGBCL with MYC and BCL2 rearrangements protects tumor cells from CD79B-directed Polatuzumab-Vedotin killing.

cancer biology↗

bioRxiv2023

ZEB1 shapes AML immunological niches suppressing CD8 T-cell activity while fostering Th17 cell expansion.

Acute myeloid leukemia (AML) development and progression is favored by immune suppression directly triggered by leukemia cells. ZEB1 is a key transcription factor in epithelial-to-mesenchymal transition which, we show here, is capable immune regulation in AML. Leukemic cells which had ZEB1 knocked down have reduced engraftment and extramedullary disease when transplanted into immune competent mice due to concomitant activation of CD8 T lymphocytes and reduced expansion of Th17 cells. Differently, in ZEB1 competent AML, IL-17 sustains the development of a pro-invasive and self-maintaining loop inducing MMPs and SOCS2. In humans, AML patients show, in situ on bone marrow biopsies, a direct correlation between ZEB1 and Th17 and, in gene expression profile when divided according to the median value of ZEB1 expression, a different overall survival and relapse along with the expression of MMPs, SOCS2 and Th17 cells enrichment. Overall, our data shed new light into the role of ZEB1 in AML that entwines both pro-tumoral and immune regulatory capacity in AML blasts.

immunology↗

bioRxiv2023

A planar-polarized MYO6-DOCK7-RAC1 axis promotes tissue fluidification in mammary epithelia

Tissue fluidification and collective motility are pivotal in regulating embryonic morphogenesis, wound healing and tumor metastasis. These processes frequently require that each cell constituent of a tissue coordinates its migration activity and directed motion through the oriented extension of lamellipodia cell protrusions, promoted by RAC1 activity. While the upstream RAC1 regulators in individual migratory cells or leader cells during invasion or wound healing are well characterized, how RAC1 is controlled in follower cells remains unknown. Here, we identify a novel MYO6-DOCK7 axis that is critical for spatially restriction of RAC1 activity in a planar polarized fashion in model tissue monolayers. The MYO6-DOCK7 axis specifically controls the extension of cryptic lamellipodia required to drive tissue fluidification and cooperative mode motion in otherwise solid and static carcinoma cell collectives. HighlightsO_LICollective motion of jammed epithelia requires myosin VI activity C_LIO_LIThe MYO6-DOCK7 axis is critical to restrict the activity of RAC1 in a planar polarized fashion C_LIO_LIMYO6-DOCK7-RAC1 activation ensures long-range coordination of movements by promoting orientation and persistence of cryptic lamellipodia C_LIO_LIMyosin VI overexpression is exploited by infiltrating breast cancer cells C_LI

cell biology↗

bioRxiv2021

DNA damage response at telomeres boosts the transcription of SARS-CoV-2 receptor ACE2 during aging

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection is known to be more common in the elderly, who show also more severe symptoms and a higher risk of hospitalization and death. Here we show that the expression of the Angiotensin Converting Enzyme 2 (ACE2), the SARS-CoV2 cell receptor, increases during aging in mouse and human lungs, and following telomere shortening or dysfunction in mammalian cells and in mouse models. This increase is regulated at the transcription level, and Ace2 promoter activity is DNA damage response (DDR)-dependent. Indeed, ATM inhibition or the selective inhibition of telomeric DDR, through the use of antisense oligonucleotides, prevents Ace2 upregulation following telomere damage, in cultured cells and in mice. We propose that during aging telomeric shortening, by triggering DDR activation, causes the upregulation of ACE2, the SARS-CoV2 cell receptor, thus making the elderly likely more susceptible to the infection.

cell biology↗

bioRxiv2021

Neutrophil extracellular traps arm DC vaccination against NPM-mutant myeloproliferation

Neutrophil extracellular traps (NET) are web-like chromatin structures composed by dsDNA and histones, decorated with anti-microbial proteins. Their interaction with dendritic cells (DC) allows DC activation and maturation toward presentation of NET-associated antigens. Differently from other types of cell death that imply protein denaturation, NETosis preserves the proteins localized onto the DNA threads for proper enzymatic activity and conformational status, including immunogenic epitopes. Besides neutrophils, leukemic cells can release extracellular traps displaying leukemia-associated antigens, prototypically mutant nucleophosmin (NPMc+) that upon mutation translocates from nucleolus to the cytoplasm localizing onto NET threads. We tested NPMc+ immunogenicity through a NET/DC vaccine to treat NPMc-driven myeloproliferation in transgenic and transplantable models. Vaccination with DC loaded with NPMc+ NET (NPMc+ NET/DC) reduced myeloproliferation in transgenic mice, favoring the development of antibodies to mutant NPMc and and the induction of a CD8+ T cell response. The efficacy of this vaccine was also tested in mixed NPMc/WT bone marrow chimeras in a competitive bone marrow transplantation setting, where the NPMc+ NET/DC vaccination impaired the expansion of NPMc+ in favor of WT myeloid compartment. NPMc+ NET/DC vaccination also achieved control of an aggressive leukemia transduced with mutant NPMc, effectively inducing an anti-leukemia CD8 T cell memory response. eTOC SummaryNPMc is an AML-triggering mutation inducing translocation of NPM into the cytoplasm, allowing its association to NET threads. On NET, NPMc becomes immunogenic acting as an alarmin and exposing immunogenic peptides. We demonstrate that NET can be exploited as anti-tumor weapons in DC-based vaccination strategies.

immunology↗

bioRxiv2020

SDF-1/CXCR4 inhibition prevents paradoxical generation of cisplatin-induced pro-metastatic niches

Platinum-based chemotherapy remains widely used in advanced non-small cell lung cancer (NSCLC) despite its ineffectiveness in long-term control of metastasis. Here, we uncover the interconnected pathways subtending cisplatin-induced metastasis promotion. We report that cisplatin treatment of tumor-free mice results in bone-marrow expansion of CCR2+CXCR4+Ly6Chigh inflammatory monocytes (IM) concomitantly with increased levels in the lungs of stromal SDF-1, the CXCR4 ligand. In experimental metastasis assays, cisplatin-induced IM favor tumor cells extravasation and expansion of CD133+CXCR4+ metastasis initiating cells (MICs), facilitating lung metastasis formation. At the primary tumor, cisplatin reduces tumor size but induces tumor release of SDF-1 triggering MICs expansion and recruitment of pro-invasive CXCR4+ macrophages. Co-recruitment of MICs and CCR2+CXCR4+ IM at SDF-1-enriched distant sites also promotes spontaneous metastasis. Combination treatment with a CXCR4 inhibitor prevents cisplatin-induced IM/MICs recruitment and interaction thus precluding metastasis overgrowth. Finally, we observe in NSCLC patients specimens that SDF-1 levels are higher in platinum-treated samples and correlate with worse outcome. Our findings suggest a possible novel combination therapy based on CXCR4 blockade to control metastatic disease, paradoxically promoted by cisplatin.

cancer biology↗

bioRxiv2020

CD40 provides immune privilege to the bone marrow hematopoietic niche

Allogeneic bone marrow transplantation remains the only therapeutic option for a wide range of hematological malignancies despite the risk of possible adverse, immune-related events, such as infection and acute graft-versus-host disease (aGVHD). aGVHD is characterized by T-cell activation, defective B-cell development and osteoblastic niche destruction in bone marrow (BM) among other issues. Transplant conditioning regimens cause excessive inflammatory cytokines production and impaired regulatory T-cell control of aberrant T-cell activation. Here, we show that mesenchymal cells (MSCs) upregulated CD40 upon irradiation at the expense of mesenchymal markers, and that CD40 endows MSC of regulatory function on Treg homeostasis and fitness. Transplantation of wild type hematopoietic cells into a CD40-null recipient reduces Treg numbers allowing persistent T-cell activation and pro-inflammatory cytokines production causing, impaired B-lymphopoiesis. These evidences find correlation in aGVHD patients showing the loss of CD40+ BM-MSCs along with reduction in cells of the B-lineage. Modeling aGVHD in mice we show that the elimination of CD40+ BM-MSCs relies on their higher expression of MHC-I molecules. Indeed, aGVHD mice compared to MHC-matched controls showed the loss of MHC-I + radio-resistant host BM-MSCs. Our data point to CD40+ MHC-I+BM-MSCs as a key regulator of BM tolerogenic niches. Key pointsO_LICD40 regulates BM immunological tolerance following total body irradiation (TBI) and transplantation (BMT). C_LIO_LILoss of CD40+MHC-IhighBM-MSCs is associated to BM manifestation of aGVHD in human and murine model. C_LI

immunology↗

bioRxiv2020

SPARC regulation of PMN clearance protects from pristane induced lupus and rheumatoid arthritis

One step along the pathogenesis of Systemic lupus erythematosus (SLE) is associated with polymorphonuclear leukocyte (PMN) death and their ineffective removal by M2-macrophages. The secreted protein acidic and rich in cysteine (SPARC) is a matricellular protein with unexpected immunosuppressive function in M2-macrophages and myeloid cells. To investigate the role of SPARC in autoimmunity, we adopted a pristane-induced model of lupus in mice, which recapitulates clinical manifestations of human SLE. Sparc-/- mice developed earlier and more severe renal disease, lung and liver parenchymal damage than the WT counterpart. Most prominently, Sparc-/- mice had anticipated and severe occurrence of arthritis. An intermediate phenotype was obtained in Sparc+/- hemizygous mice, a result that suggests Sparc gene-dosage as relevant in autoimmune-related events. Mechanistically, a defective Sparc expression in PMN blocks their clearance by macrophages, through a defective delivery of eat-me and dont eat-me signals. Sparc-/- PMN that escape macrophage scavenging becomes a source of autoantigens for dendritic cell (DC) presentation and a direct stimulus for IL-17 expression in {gamma}{delta}-T-cells. Gene profile analysis of synovial biopsies of knees affected by SLE-associated arthritis showed an inverse correlation between SPARC and key autoimmune genes. These results point to SPARC down-regulation as a key event characterizing SLE and associated rheumatoid arthritis pathogenesis.

immunology↗

bioRxiv2020

PD-1-induced T cell exhaustion is controlled by a Drp1-dependent mechanism

PD-1 signalling downregulates the T cell response, promoting an exhausted state in tumor-infiltrating T cells, through mostly unveiled molecular mechanisms. Drp1-dependent mitochondrial fission plays a crucial role to sustain T cell motility, proliferation, survival and glycolytic engagement and, interestingly, such processes are exactly those inhibited by PD-1 in tumor-infiltrating T cells. Here we show that the signature of PD-1pos CD8+ T cells infiltrating MC38-derived murine tumor mass is having downregulated Drp1 activity and more fused mitochondria, compared to PD-1neg counterparts. Also, PD-1pos lymphocytic elements infiltrating human colon cancer rarely express active Drp1. Mechanistically, PD-1 signalling directly prevents mitochondria fragmentation following T cell stimulation by downregulating Drp1 phosphorylation on Ser616, via regulation of the ERK1/2 and mTOR pathways. In addition, downregulation of Drp1 activity in tumor-infiltrating PD-1pos CD8+ T cells seems to be a mechanism exploited by PD-1 signalling to reduce motility and proliferation of these cells. Overall, our data indicate that the modulation of Drp1 activity in tumor-infiltrating T cells may become a valuable target to ameliorate the anti-cancer immune response in future immunotherapy approaches.

immunology↗

bioRxiv2020

Intra-tumor heterogeneity of Diffuse Large B-cell Lymphoma involves the induction of diversified stroma-tumor interfaces

Intra-tumor heterogeneity in lymphoid malignancies is articulated around several fundamentals, encompassing selection of genetic subclonal events and epigenetic regulation of transcriptional programs. Clonally-related neoplastic cell populations are unsteadily subjected to immune editing and metabolic adaptations within different tissue microenvironments. How tissue-intrinsic mesenchymal determinants impact on the diversification of aggressive lymphomas is still unknown. In this study we adopted the established A20 line-based model of Diffuse Large B-cell Lymphoma (DLBCL), to investigate the intra-tumor heterogeneity associated with the infiltration of different tissue microenvironments and the specific mesenchymal modifications that characterize stromal adaptation to lymphoma seeding. Combining in situ quantitative immunophenotypical analyses and RNA sequencing, we found that the tissue microenvironment casts a relevant influence over A20 transcriptional landscape also impacting on Myc and DNA damage response programs. Extending the investigation to mice deficient for the matricellular protein Sparc, a stromal determinant endowed with a strong prognostic significance in human DLBCL, we demonstrated a different immune imprint on A20 cells related to stromal Sparc proficiency. The study provides the first evidence of human DLBCL intra-lesional heterogeneity arising from diversified mesenchymal contextures and impacting on MYC expression, advancing the challenge for resolving intra-tumor heterogeneity probing stromal/immune interfaces. KEY POINTSO_LIDiversified stromal adaptations of infiltrated tissues shape DLBCL intra-tumor heterogeneity regulating transcriptional/phenotypic features C_LIO_LIStromal Sparc, which endorses prognostic significance in DLBCL, tunes the immune pressure exerted on lymphoma cells by the microenvironment C_LI

cancer biology↗

bioRxiv2020

Compromised nuclear envelope integrity drives tumor cell invasion

While mutations leading to a fragile envelope of the cell nucleus are well known to cause diseases such as muscular dystrophies or accelerated aging, the pathophysiological consequences of the recently discovered mechanically induced nuclear envelope ruptures in cells harboring no mutation are less known. Here we show that repeated loss of nuclear envelope integrity in nuclei experiencing mechanical constraints promotes senescence in nontransformed cells, and induces an invasive phenotype including increased collagen degradation in human breast cancer cells, both in vitro and in a mouse xenograft model of breast cancer progression. We show that these phenotypic changes are due to the presence of chronic DNA damage and activation of the ATM kinase. In addition, we found that depletion of the cytoplasmic exonuclease TREX1 is sufficient to abolish the DNA damage in mechanically challenged nuclei and to suppress the phenotypes associated with the loss of nuclear envelope integrity. Our results also show that TREX1-dependent DNA damage induced by physical confinement of tumor cells inside the mammary duct drives the progression of in situ breast carcinoma to the invasive stage. We propose that DNA damage in mechanically challenged nuclei could affect the pathophysiology of crowded tissues by modulating proliferation and extracellular matrix degradation of normal and transformed cells.

cell biology↗

bioRxiv2020

ATR expands embryonic stem cell fate potential in response to replication stress

Unrepaired DNA damage during embryonic development can be potentially inherited by a large population of cells. However, the quality control mechanisms that minimize the contribution of damaged cells to developing embryos remain poorly understood. Here, we uncovered an ATR- and CHK1-mediated transcriptional response to replication stress (RS) in ESCs that induces genes expressed in totipotent two-cell (2C) stage embryos and 2C-like cells. This response is mediated by Dux, a multicopy retrogene defining the cleavage-specific transcriptional program in placental mammals. In response to RS, DUX triggers the transcription of 2C-like markers such as murine endogenous retrovirus-like elements (MERVL) and Zscan4. This response can also be elicited by ETAA1-mediated ATR activation in the absence of RS. ATR-mediated activation of DUX requires GSRF1 dependent post-transcriptional regulation of Dux mRNA. Strikingly, activation of ATR expands ESCs fate potential by extending their contribution to both embryonic and extra{-}embryonic tissues. These findings define a novel ATR dependent pathway involved in maintaining genome stability in developing embryos by controlling ESCs fate in response to RS.

cell biology↗

bioRxiv2019

IRSp53 shapes the plasma membrane and controls polarized transport at the nascent lumen during epithelial morphogenesis

Establishment of apical-basal cell polarity is necessary for generation of luminal and tubular structures during epithelial morphogenesis. Molecules acting at the membrane/ actin interface are expected to be crucial in governing these processes. Here, we show that the I-BAR-containing IRSp53 protein is restricted to the luminal side of epithelial cells of various glandular organs, and is specifically enriched in renal tubules in human, mice, and zebrafish. Using three-dimensional cultures of renal MDCK and intestinal Caco-2 cysts, we show that IRSp53 is recruited early after the first cell division along the forming apical lumen, and is essential for formation of a single lumen and for positioning of the polarity determinants aPKC and podocalyxin. Molecularly, IRSp53 directly binds to and controls localization of the inactive form of the small GTPase RAB35, a tethering factor for apical determinants. The interaction of IRSp53 with the actin capping protein EPS8 is critical for restricting IRSp53 localization. Correlative light and electron microscopy shows that IRSp53 loss perturbs the shape and continuity of the opposing apical membrane during the initial phase of lumenogenesis, which leads to preservation of multiple cytoplasmic bridges that interrupt the continuity of the nascent lumen. At the organism level, genetic removal of IRSp53 results in abnormal renal tubulogenesis, with defects in tubular polarity and architectural organization in both IRSp53 zebrafish mutant lines and IRSp53-KO murine models. Thus, IRSp53 acts as a platform for spatiotemporal regulation of assembly of the multi-protein complexes that shape the luminal membrane during the early steps of epithelial lumen morphogenesis.

developmental biology↗