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.
GrantsVictoria Brain Bank Fidelity Trust EAN Michael J. Fox Foundation (MJFF) FARA National Institute for Health Research University College London Hospitals Biomedical Research Centre (NIHR-BRC) MSA Trust MRC GERF-STDF NRF - Ministry of Science and ICT National Research Foundation of Korea (NRF) - Ministry of Science and ICT UCL Global Engagement Fund scheme Wellcome Trust Rosetrees Trust NIH NeuroBioBank Dolby Family Fund
Cerebral Palsy Alliance Guarantors of Brain DFG Parkinson's Foundation European Union Parkinson Disease Society Deutsche Forschungsgemeinschaft (DFG MSA Coalition MRC Brainbank Network Alzheimer's Research UK (ARUK) Queen Square BrainBank Nile of Hope Hospital for Congenital Anomalies, Alexandria, Egypt