Simultaneous impairment of neuronal and metabolic function of mutated gephyrin in a patient with epileptic encephalopathy.

Synaptic inhibition is essential for shaping the dynamics of neuronal networks, and aberrant inhibition plays an important role in neurological disorders. Gephyrin is a central player at inhibitory postsynapses, directly binds and organizes GABAA and glycine receptors (GABAARs and GlyRs), and is thereby indispensable for normal inhibitory neurotransmission. Additionally, gephyrin catalyzes the synthesis of the molybdenum cofactor (MoCo) in peripheral tissue. We identified a de novo missense mutation (G375D) in the gephyrin gene (GPHN) in a patient with epileptic encephalopathy resembling Dravet syndrome. Although stably expressed and correctly folded, gephyrin-G375D was non-synaptically localized in neurons and acted dominant-negatively on the clustering of wild-type gephyrin leading to a marked decrease in GABAAR surface expression and GABAergic signaling. We identified a decreased binding affinity between gephyrin-G375D and the receptors, suggesting that Gly375 is essential for gephyrin-receptor complex formation. Surprisingly, gephyrin-G375D was also unable to synthesize MoCo and activate MoCo-dependent enzymes. Thus, we describe a missense mutation that affects both functions of gephyrin and suggest that the identified defect at GABAergic synapses is the mechanism underlying the patient's severe phenotype.

Dejanovic B ，Djémié T ，Grünewald N ，Suls A ，Kress V ，Hetsch F ，Craiu D ，Zemel M ，Gormley P ，Lal D ，EuroEPINOMICS Dravet working group ，Myers CT ，Mefford HC ，Palotie A ，Helbig I ，Meier JC ，De Jonghe P ，Weckhuysen S ，Schwarz G ... -  《-》

A mutation in the gene for the neurotransmitter receptor-clustering protein gephyrin causes a novel form of molybdenum cofactor deficiency.

Reiss J ，Gross-Hardt S ，Christensen E ，Schmidt P ，Mendel RR ，Schwarz G ... -  《-》

Duplicated gephyrin genes showing distinct tissue distribution and alternative splicing patterns mediate molybdenum cofactor biosynthesis, glycine receptor clustering, and escape behavior in zebrafish.

Ogino K ，Ramsden SL ，Keib N ，Schwarz G ，Harvey RJ ，Hirata H ... -  《-》

Biallelic gephyrin variants lead to impaired GABAergic inhibition in a patient with developmental and epileptic encephalopathy.

Synaptic inhibition is essential for shaping the dynamics of neuronal networks, and aberrant inhibition is linked to epilepsy. Gephyrin (Geph) is the principal scaffolding protein at inhibitory synapses and is essential for postsynaptic clustering of glycine (GlyRs) and GABA type A receptors. Consequently, gephyrin is crucial for maintaining the relationship between excitation and inhibition in normal brain function and mutations in the gephyrin gene (GPHN) are associated with neurodevelopmental disorders and epilepsy. We identified bi-allelic variants in the GPHN gene, namely the missense mutation c.1264G > A and splice acceptor variant c.1315-2A > G, in a patient with developmental and epileptic encephalopathy. We demonstrate that the splice acceptor variant leads to nonsense-mediated mRNA decay. Furthermore, the missense variant (D422N) alters gephyrin structure, as examined by analytical size exclusion chromatography and circular dichroism-spectroscopy, thus leading to reduced receptor clustering and sensitivity towards calpain-mediated cleavage. In addition, both alterations contribute to an observed reduction of inhibitory signal transmission in neurons, which likely contributes to the pathological encephalopathy.

Macha A ，Liebsch F ，Fricke S ，Hetsch F ，Neuser F ，Johannes L ，Kress V ，Djémié T ，Santamaria-Araujo JA ，Vilain C ，Aeby A ，Van Bogaert P ，Dejanovic B ，Weckhuysen S ，Meier JC ，Schwarz G ... -  《-》

Splice-specific functions of gephyrin in molybdenum cofactor biosynthesis.

Smolinsky B ，Eichler SA ，Buchmeier S ，Meier JC ，Schwarz G ... -  《JOURNAL OF BIOLOGICAL CHEMISTRY》