Biology subjects

Bidaud-Meynard, A.

Publications and source records attributed to Bidaud-Meynard, A..

6 recordsLinked to original sources

bioRxiv2023

The clathrin adaptor AP-1B independently controls proliferation and differentiation in the mammalian intestine.

Maintenance of the polarity of the epithelial cells facing the lumen of the small intestine is crucial to ensure the vectorial absorption of nutrients as well as the integrity of the apical brush border and the intestinal barrier. Polarized vesicular trafficking plays a key role in this process, and defective transport due to mutations in apical trafficking-related genes has been shown to affect nutrient absorption. Interestingly, it has been demonstrated that downregulation of the polarized sorting clathrin adaptor AP-1B led to both epithelial polarity and proliferation defects in the mouse intestine. This enlightened a new function of polarized trafficking in the gut epithelium and a novel link between trafficking, polarity, and proliferation. Here, using CRISPR-Cas9-mediated mutation of the AP-1B coding gene Ap1m2 in mouse intestinal organoids, we uncovered a novel proliferation pathway controlled by AP-1B. We showed that the polarity defects induced by Ap1m2 mutations led to a defective apical targeting of both Rab11+ apical recycling endosomes and of the polarity determinant Cdc42. Moreover, we showed that these polarity defects were accompanied by an induction of YAP and EGFR/mTOR-dependent proliferation pathways. Finally, we showed that AP-1B additionally controlled a proliferation-independent differentiation pathway towards the secretory lineage. Overall, our results highlighted the pleiotropic roles played by AP-1B in the homeostasis of the gut epithelium.

cell biology↗

bioRxiv2022

V0-ATPase downregulation induces MVID-like brush border defects independently of apical trafficking in the mammalian intestine

SummaryIntestinal microvillus atrophy is a major cause of enteropathies such as idiopathic or congenital diarrhea that are often associated with severe morbidity. It can be caused by genetic disorders, inflammatory diseases, toxins or pathogens. In particular, Microvillus inclusion disease (MVID) is characterized by a chronic intractable diarrhea and a severe microvillus atrophy. It is triggered by mutations in MYO5B, STX3, MUNC18.2 or UNC45A which alter epithelial polarity by affecting apical trafficking in intestinal epithelial cells. Furthermore, we recently established that the depletion of the V0 sector of the V-ATPase complex induces an MVID-like phenotype in C. elegans. In this study we investigated the function of the V0-ATPase complex in mouse intestinal organoids. We found that its depletion also triggers a very severe microvillus atrophy in this model. Furthermore, we established that the polarity of intestinal cells is affected in a patient carrying mutations in TCIRG1 which encodes a V0-ATPase subunit. However, V0- ATPase depletion does not recapitulate other MVID-specific phenotypes such as subapical vesicle accumulation and Rab11+ endosomes mislocalization. Finally, we found that the apical localization of the V0-ATPase is disrupted in MVID patients. Altogether these results suggest a role for the V0-ATPase in microvillus atrophy which might be independent from apical trafficking.

cell biology↗

bioRxiv2021

High-resolution reconstruction and deconvolution of array detector images

Array detector allows a resolution gain for confocal microscopy by combining images sensed by a set of photomultipliers tubes (or sub-detectors). Several methods have been proposed to reconstruct a high resolution image by linearly combining sub-detector images. To overcome the limitations of these techniques, we propose a new reconstruction method that takes the full stack of spatially reassigned detector signals as input. We show on both calibration slides and real data that our deconvolution method allows to achieve a better reconstruction performance in terms of resolution, image contrast, and spatial intensity homogeneity. The tested algorithms are available in an open source software.

bioinformatics↗

bioRxiv2021

High resolution dynamic mapping of the C. elegans intestinal brush border

The intestinal brush border is made of an array of microvilli that increases the membrane surface area for nutrient processing, absorption, and host defence. Studies on mammalian cultured epithelial cells uncovered some of the molecular players and physical constrains required to establish this apical specialized membrane. However, the building and maintenance of a brush border in vivo has not been investigated in detail yet. Here, we combined super-resolution imaging, transmission electron microscopy and genome editing in the developing nematode C. elegans to build a high-resolution and dynamic localization map of known and new markers of the brush border. Notably, we show that microvilli components are dynamically enriched at the apical membrane during microvilli outgrowth and maturation but become highly stable once microvilli are built. This new mapping tool will be instrumental to understand the molecular processes of microvilli growth and maintenance in vivo as well as the effect of genetic perturbations, notably in the context of disorders affecting brush border integrity.

developmental biology↗

bioRxiv2018

The loss of V0-ATPase induces Microvillus inclusion-like disease in C. elegans

Intestine function relies on the strong polarity of intestinal epithelial cells and the array of microvilli forming a brush border at their luminal pole. Combining genetic RNAi screen and in vivo super-resolution imaging in the C. elegans intestine, we uncovered that the V0 sector of the V-ATPase (V0-ATPase) controls a late apical trafficking step, involving RAB-11 endosomes and the SNARE SNAP-29, necessary to maintain the polarized localization of both apical polarity modules and brush border proteins. We show that the V0-ATPase pathway also genetically interacts with glycosphingolipids in enterocyte polarity maintenance. Finally, we demonstrate that depletion of the V0-ATPase fully recapitulates the severe structural, polarity and trafficking defects observed in enterocytes from patients with Microvillus inclusion disease (MVID) and used this new in vivo MVID model to follow the dynamics of microvillus inclusions. Hence, we describe a new function for the V0-ATPase in apical trafficking and epithelial polarity maintenance and the promising use of C. elegans intestine as an in vivo model to better understand the molecular mechanisms of rare genetic enteropathies.\n\nSummary statementV0-ATPase controls a late apical trafficking step involved in the maintenance of the apical absorptive intestinal membrane and its depletion phenocopies the trafficking and structural defects of MVID in C. elegans.

cell biology↗

bioRxiv2018

Transcytosis maintains CFTR apical polarity in the face of constitutive and mutation-induced basolateral missorting

Apical polarity of cystic fibrosis transmembrane conductance regulator (CFTR) is essential for solute and water transport in secretory epithelia and can be impaired in human diseases. Maintenance of apical polarity in the face of CFTR non-polarized delivery and compromised apical retention of mutant CFTRs lacking PDZ-domain protein (NHERF1) interaction, remains enigmatic. Here we show that basolateral CFTR delivery originates from biosynthetic (~35%) and endocytic (~65%) recycling missorting. Basolateral channels are retrieved via basolateral-to-apical transcytosis, enhancing CFTR apical expression by two-fold and suppressing its degradation. CFTR transcytosis is microtubule-dependent but independent of Myo5B-, Rab11- and NHERF1 binding to its C-terminal DTRL motif in airway epithelia. Increased basolateral delivery due to compromised apical recycling and accelerated internalization upon impaired NHERF1-CFTR association is largely counterbalanced by CFTR efficient basolateral internalization and apical transcytosis. Thus, transcytosis represents a previously unrecognized but indispensable mechanism for maintaining CFTR apical polarity by attenuating its constitutive and mutation-induced basolateral missorting.

cell biology↗