MDGA2 encodes a membrane-associated protein that is critical for regulating glutamatergic synapse development, modulating neuroligins (Nlgns), and maintaining excitatory-inhibitory synaptic balance. While MDGA2 functions have been extensively studied in murine and cellular models, its association with human developmental disorders has yet to be established. Through exome sequencing, we identified seven distinct homozygous loss-of-function variants in MDGA2 in nine individuals from seven consanguineous families, all presenting with developmental and epileptic encephalopathy (DEE). Clinically, these individuals exhibited a consistent phenotype including infantile hypotonia, severe neurodevelopmental delay, intractable seizures, along with distinct dysmorphic features. Neuroimaging findings included delayed/incomplete myelination, early-onset brain atrophy, white-matter thinning, basal ganglia volume loss, and small hippocampi. Functional studies of three representative nonsense variants revealed impaired MDGA2 membrane trafficking, disrupted Nlgn1 interaction, and perturbed MDGA2-mediated excitatory synaptic functions in mammalian expression systems and cultured hippocampal neurons. Our findings support the involvement of MDGA2 in a subtype of autosomal-recessive DEE. This not only underscores a loss-of-function pathogenic mechanism but also highlights the previously unrecognized role of MDGA2 in human synaptic development and regulation, significantly expanding our understanding of the genetic architecture of DEEs.
FörderungenNile of Hope Hospital for Congenital Anomalies, Alexandria, Egypt Wellcome Trust UCL Global Engagement Fund scheme National Research Foundation of Korea (NRF) - Ministry of Science and ICT NRF - Ministry of Science and ICT GERF-STDF MRC MSA Trust National Institute for Health Research University College London Hospitals Biomedical Research Centre (NIHR-BRC) FARA Michael J. Fox Foundation (MJFF) EAN Fidelity Trust Victoria Brain Bank Rosetrees Trust NIH NeuroBioBank Dolby Family Fund Queen Square BrainBank Alzheimer's Research UK (ARUK) MRC Brainbank Network MSA Coalition Deutsche Forschungsgemeinschaft (DFG Parkinson Disease Society European Union Parkinson's Foundation DFG Guarantors of Brain Cerebral Palsy Alliance