Biology subjects

Raveenthiraraj, S.

Publications and source records attributed to Raveenthiraraj, S..

3 recordsLinked to original sources

bioRxiv2023

WNT2B Deficiency Causes Increased Susceptibility to Colitis in Mice and Impairs Intestinal Epithelial Development in Humans

Background and aimsWNT2B is a canonical Wnt ligand previously thought to be fully redundant with other Wnts in the intestinal epithelium. However, humans with WNT2B deficiency have severe intestinal disease, highlighting a critical role for WNT2B. We sought to understand how WNT2B contributes to intestinal homeostasis. MethodsWe investigated the intestinal health of Wnt2b knock out (KO) mice. We assessed the impact of inflammatory challenge to the small intestine, using anti-CD3{chi} antibody, and to the colon, using dextran sodium sulfate (DSS). In addition, we generated human intestinal organoids (HIOs) from WNT2B-deficient human iPSCs for transcriptional and histological analyses. ResultsMice with WNT2B deficiency had significantly decreased Lgr5 expression in the small intestine and profoundly decreased expression in the colon, but normal baseline histology. The small intestinal response to anti-CD3{chi} antibody was similar in Wnt2b KO and wild type (WT) mice. In contrast, the colonic response to DSS in Wnt2b KO mice showed an accelerated rate of injury, featuring earlier immune cell infiltration and loss of differentiated epithelium compared to WT. WNT2B-deficient HIOs showed abnormal epithelial organization and an increased mesenchymal gene signature. ConclusionWNT2B contributes to maintenance of the intestinal stem cell pool in mice and humans. WNT2B deficient mice, which do not have a developmental phenotype, show increased susceptibility to colonic injury but not small intestinal injury, potentially due to a higher reliance on WNT2B in the colon compared to the small intestine. WNT2B deficiency causes a developmental phenotype in human intestine with HIOs showing a decrease in their mesenchymal component and WNT2B-deficient patients showing epithelial disorganization. Data Transparency StatementAll RNA-Seq data will be available through online repository as indicated in Transcript profiling. Any other data will be made available upon request by emailing the study authors.

molecular biology↗

bioRxiv2022

Hepatocyte Growth Factor and β1-integrin signalling axis drives tunneling nanotube formation in A549 lung adenocarcinoma cells

Tunneling nanotubes (TNTs) are thin cytoplasmic protrusions involved in long-distance cellular communication. The presence of TNTs has been found in vivo and in vitro studies in non-small cell lung cancer (NSCLC). Cancer cells transport a range of organelles and signalling molecules along TNTs, to confer a survival phenotype for the recipient cell, contributing toward chemoresistance and malignancy. Despite its important role in cancer progression, the molecular mechanisms underlying TNT formation is not well defined. Within the tumour microenvironment (TME) of NSCLC, hepatocyte growth factor (HGF) and its receptor, c-Met, are mutationally upregulated causing growth, and invasion. In this study, we report a novel crosstalk between HGF/c-Met and {beta}1-integrin involved in the formation of functional TNTs in A549 cells. Through pharmacological inhibitor studies, we discovered Arp2/3 complex, MAPK and PI3K pathways were activated downstream of this crosstalk signalling axis. Furthermore, paxillin was recruited during this key process, localising at the protrusion site of HGF-induced TNTs, and therefore serving as the central link between the upstream and downstream regulators involved. Overall, these results demonstrate a novel strategy to inhibit TNT formation in NSCLC through targeting the HGF/c-Met and {beta}1-integrin signalling axis, thus highlighting the importance of personalised multi-drug targeting in NSCLC.

cancer biology↗

bioRxiv2022

M1 and M2 macrophages differentially regulate colonic crypt renewal.

The colonic epithelium is the most rapidly renewing tissue in the body and is organized into a single cell layer of invaginations called crypts. Crypt renewal occurs through Lgr5+ gut stem cells situated at the crypt base, which divide, produce daughter cells that proliferate, migrate, differentiate into all the cells required for normal gut function (eg. Goblet cells, enterocytes), and are finally shed into the crypt lumen. In health this rapid renewal helps maintain barrier function next to the hostile gut luminal environment that contains microbes and food. In parallel, the peri-cryptal lamina propria hosts the largest monocyte-derived macrophage population in the human body. Different macrophage phenotypes have been associated with intestinal health/intact barrier function, namely M2 compared to M1 macrophages that indicate inflammation/compromised barrier function. However, the direct effect of different macrophage subtypes have on colonic crypt renewal is not well understood. In this study we have utilized a reductionist 3D in vitro co-culture model to determine the regulatory capacity of M1 and M2 macrophages on colonic crypt renewal. We show that colonic crypt proliferation is increased in the presence of M1 or M2 macrophages, while we further demonstrate that a decrease in goblet and tuft cell expression as well as an increase in Lgr5+ stem cell numbers is only achieved through M1-crypt crosstalk in a contact dependent manner.

cell biology↗