DENND5A-related developmental and epileptic encephalopathy driven by loss of symmetric cell division of apical neural progenitors

Developmental and epileptic encephalopathies (DEE) are a heterogenous group of epilepsies in which altered brain development can lead to developmental delay and seizures, with the epileptic activity further negatively impacting neurodevelopment[1][1]. Identifying the underlying cause of DEE is essential for progress towards precision therapy. Here we describe a group of patients with DEE that exhibit a unique cluster of neuroanatomical signatures due to biallelic variants in DENND5A . We demonstrate that DENND5A interacts with MUPP1 and PALS1, components of the Crumbs apical polarity complex, which is required for both neural progenitor cell identity and the ability of these stem cells to divide symmetrically[2][2]. Induced pluripotent stem cells lacking DENND5A fail to undergo symmetric cell division during neural induction and have an inherent propensity to differentiate into neurons. Similarly, transgenic DENND5A mice, with phenotypes consistent with the human syndrome, have an increased number of neurons in the proliferative adult subventricular zone. Disruption of symmetric cell division following loss of DENND5A results from misalignment of the mitotic spindle in apical neural progenitors, an observation also observed in PALS1 null zebrafish embryos[3][3]. This orients cells away from the proliferative apical domain surrounding the ventricles, biasing daughter cells towards a more fate-committed state, and ultimately halting neurodevelopment. This study provides a mechanism behind DENND5A -related DEE that may also be generalizable to other developmental conditions and provides variant-specific clinical information for physicians and families. ### Competing Interest Statement KM and RP are employed by GeneDx, LLC. All other authors report no conflicts of interest. ### Funding Statement Participant 10 was recruited as part of the German-Jordanian Autosomal Recessive Intellectual Disability project (GeJo-ARID) funded by the German Academic Exchange Service (DAAD) as part of the German-Arab Transformation Program Line4 (Project-ID 57166498). This work was funded by a Foundation Grant from the Canadian Institutes of Health Research to PSM and a grant from the Alain and Sandra Bouchard Foundation for Intellectual Disabilities to PSM and TMD. This work was also supported by the King Salman Center for Disability Research through Research Group no RG-2022-010 (FSA). This work was also performed under the Care4Rare Canada Consortium funded by Genome Canada and the Ontario Genomics Institute (OGI-147), the Canadian Institutes of Health Research, Ontario Research Fund, Genome Alberta, Genome British Columbia, Genome Quebec, and Childrens Hospital of Eastern Ontario Foundation (DC, ESYG, MO). Research reported in this manuscript was also supported by the NIH Common Fund, through the Office of Strategic Coordination/Office of the NIH Director under Award Number(s) \[U01HG007672, U01HG007943\] (HC) and \[NS105078, HG011758\] (JRL). ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: All materials and methods for participant recruitment and clinical data collection was approved by the McGill University Health Centre research ethics board (study 2021-6324) and the McGill Faculty of Medicine and Health Sciences institutional review board (study A12-M66-21B). I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines and uploaded the relevant EQUATOR Network research reporting checklist(s) and other pertinent material as supplementary files, if applicable. Yes Supplementary table 1 includes all raw data obtained in the cohort study and describes a clinical description of each participant, as well as sums and averages of phenotypes for the whole cohort. Raw data concerning in vitro cell experiments and in vivo and ex vivo mouse experiments were generated at the Montreal Neurological Institute of McGill University. Source data for all major experiments in the study have been uploaded to Figshare and are additionally available in Supplementary Information. [1]: #ref-1 [2]: #ref-2 [3]: #ref-3