Missense variants in DPYSL5 associated with neurodevelopmental disorders and brain malformations cause impaired neuronal maturation in vitro

Neurodevelopmental disorders (NDD) with brain malformations have recently been associated with de novo variants in the DPYSL5 gene, which encodes a member of the dihydropyrimidinase-like proteins family. Here, we aimed to understand its role in NDD by characterizing novel or recurrent de novo variants at the molecular and cellular levels. We collected clinical data on individuals in whom DPYSL5 missense variants were identified through clinical genetic assessment of NDD or following the identification of brain malformations in fetuses. Functional analyses of wild-type and variant DPYSL5 proteins were performed to evaluate their impact on in vitro neuronal development and maturation, using primary neuronal cultures from mouse embryonic brains or hiPSC-derived human neural stem cells. We describe six different missense variants in DPYSL5 in nine individuals (including three fetuses), including the previously identified p.(Glu41Lys) recurrent mutation (in 2 individuals), a novel recurrent missense p.(Glu25Lys) de novo variant (in 3 individuals including 2 fetuses), and 3 novel candidates. Common features were developmental delay, intellectual disability, as well as brain malformations including agenesis of the corpus callosum for the N-terminal variants. Functional assays in differentiating mouse or human neuronal cultures revealed impairments in dendritic arborization, axonal elongation, and synaptic density. We thus expanded the functional characterization of DPYSL5 variants in NDD with brain malformations, including at the fetal stage, highlighting a fundamental role of the DPYSL5 gene in brain formation and functioning.