bioRxiv preprint doi: https://doi.org/10.1101/2020.08.17.254037; this version posted August 17, 2020. The copyright holder for this preprint (which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is made available under aCC-BY-NC-ND 4.0 International license. 1 2 Endosomal trafficking defects alter neural progenitor proliferation 3 and cause microcephaly 4 5 Jacopo A. Carpentieri1, Amandine Di Cicco1, David Andreau1, Laurence Del Maestro2, Fatima 6 El Marjou1, Laure Coquand1, Jean-Baptiste Brault1, Nadia Bahi-Buisson3, Alexandre D. 7 Baffet1,4,# 8 9 1- Institut Curie, PSL Research University, CNRS UMR144, 75005 Paris, France 10 2- Centre Épigénétique et destin cellulaire, Université Paris Diderot, CNRS UMR 7216, 75013 Paris, 11 France 12 3- INSERM U1163, Institut Imagine, Necker Hospital, 75015 Paris, France 13 4- Institut national de la santé et de la recherche médicale (Inserm) 14 # Corresponding author:
[email protected] 15 16 Abstract 17 Primary microcephaly and megalencephaly are severe brain malformations defined by reduced 18 and increased brain size, respectively. Whether these two pathologies arise from related alterations at 19 the molecular level is unclear. Microcephaly has been largely associated with centrosomal defects, 20 leading to cell death. Here, we investigated the consequences of WDR81 loss of function, which cause 21 severe microcephaly in patients. We show that WDR81 regulates endosomal trafficking of EGFR, 22 and that loss of function leads to reduced MAP kinase pathway activation. Mouse radial glial 23 progenitor cells knocked-out for WDR81 display reduced proliferation rates, leading to reduced brain 24 size.