UNC45A deficiency causes microvillus inclusion disease–like phenotype by impairing myosin VB–dependent apical trafficking
Rémi Duclaux‐Loras, Corinne Lebreton, Jérémy Berthelet, Fabienne Charbit‐Henrion, Ophélie Nicolle, Céline Revenu, Stephanie Waich, Taras Valovka, Anis Khiat, Marion Rabant, Caroline Racine, Ida Chiara Guerrera, Júlia Baptista, Maxime M. Mahé, Michael W. Hess, Béatrice Durel, Nathalie Lefort, Céline Banal, Mélanie Parisot, Cécile Talbotec, Florence Lacaille, Emmanuelle Ecochard‐Dugelay, Arzu Meltem Demir, Georg F. Vogel, Laurence Bonhomme‐Faivre, Astor Rodrigues, Darren Fowler, Andreas Janecke, Thomas Müller, Lukas A. Huber, Fernando Rodrigues‐Lima, Frank M. Ruemmele, Holm H. Uhlig, Filippo Del Bene, Grégoire Michaux, Nadine Cerf–Bensussan, Marianna Parlato
Abstract
in life (1, 2). Depending on the mechanism, diarrhea can be the only symptom or one manifestation of a more complex syndrome involving several organs. A syndrome that variably combines congenital diarrhea, cholestasis, loss of hearing, and bone fragility was recently described in 3 families and ascribed to loss-of-function (LoF) variants in UNC45A (3). A zebrafish model of unc45a deficiency showed abnormal development of epithelial folds in the proximal intestine and impaired intestinal motility (3). Yet the exact mechanism underlying intestinal symptoms remains poorly characterized. UNC45A belongs to the conserved UNC45/CRO1/ She4p (UCS) protein family of myosin cochaperones, which participates in myosin-dependent functions, including cytokinesis, Variants in the UNC45A cochaperone have been recently associated with a syndrome combining diarrhea, cholestasis, deafness, and bone fragility. Yet the mechanism underlying intestinal failure in UNC45A deficiency remains unclear. Here, biallelic variants in UNC45A were identified by next-generation sequencing in 6 patients with congenital diarrhea. Corroborating in silico prediction, variants either abolished UNC45A expression or altered protein conformation. Myosin VB was identified by mass spectrometry as client of the UNC45A chaperone and was found misfolded in UNC45A KO Caco-2 cells. In keeping with impaired myosin VB function, UNC45A KO Caco-2 cells showed abnormal epithelial morphogenesis that was restored by full-length UNC45A, but not by mutant alleles. Patients and UNC45A KO 3D organoids displayed altered luminal development and microvillus inclusions, while 2D cultures revealed Rab11 and apical transporter mislocalization as well as sparse and disorganized microvilli. All those features resembled the subcellular abnormalities observed in duodenal biopsies from patients with microvillus inclusion disease. Finally, microvillus inclusions and shortened microvilli were evidenced in enterocytes from unc45a-deficient zebrafish. Taken together, our results provide evidence that UNC45A plays an essential role in epithelial morphogenesis through its cochaperone function of myosin VB and that UNC45A loss causes a variant of microvillus inclusion disease.