VAMP2 encodes the vesicular SNARE protein VAMP2 (also called synaptobrevin-2). Together with its partners syntaxin-1A and synaptosomal-associated protein 25 (SNAP25), VAMP2 mediates fusion of synaptic vesicles to release neurotransmitters. VAMP2 is essential for vesicular exocytosis and activity-dependent neurotransmitter release. Here, we report five heterozygous de novo mutations in VAMP2 in unrelated individuals presenting with a neurodevelopmental disorder characterized by axial hypotonia (which had been present since birth), intellectual disability, and autistic features. In total, we identified two single-amino-acid deletions and three non-synonymous variants affecting conserved residues within the C terminus of the VAMP2 SNARE motif. Affected individuals carrying de novo non-synonymous variants involving the C-terminal region presented a more severe phenotype with additional neurological features, including central visual impairment, hyperkinetic movement disorder, and epilepsy or electroencephalography abnormalities. Reconstituted fusion involving a lipid-mixing assay indicated impairment in vesicle fusion as one of the possible associated disease mechanisms. The genetic synaptopathy caused by VAMP2 de novo mutations highlights the key roles of this gene in human brain development and function.

Arterial stiffness is increased in children and young adults treated with the ketogenic diet, before the increase of the intima media thickness. This supports that arterial stiffness is an early marker of vascular damage.

De novo mutations in the GRIN1 gene have been recently reported as the molecular cause of a broad-spectrum early-onset neurological phenotype. Here, we describe a five-year-old girl with an early-onset epileptic encephalopathy associated with an infantile hyperkinetic movement disorder and oculomotor abnormalities. Whole-exome sequencing identified a novel p.Met641Leu de novo variant in the GRIN1 gene as the cause of the phenotype. In silico analysis suggested that the p.Met641Leu variant would alter the gating property of the ion channel, with the involved methionine residue facing towards the ion pore. Long-term systematic video-EEG allowed us to report on the electroclinical history and, specifically, on the semiology of the hyperkinetic movement disorder and oculomotor abnormalities resembling oculogyric crises in our patient. Our findings and a review of the recent literature reinforce the notion of GRIN1encephalopathy as a recognizable neurological phenotype that should be suspected in early-onset epilepsy associated with hyperkinetic movement disorders. [Published with video sequence on www.epilepticdisorders.com]

Biallelic mutations in the SLC1A4 gene have been identified as a very rare cause of neurodevelopmental disorders. l-serine transport deficiency has been regarded as the causal molecular mechanism underlying the neurological phenotype of SLC1A4 mutation patients. To date this genetic condition has been reported almost exclusively in a limited number of Ashkenazi-Jewish individuals and as a result the SLC1A4 gene is not routinely included in the majority of the genetic diagnostic panels for neurological diseases. We hereby report a 7-year-old boy from a Southern Italian family, presenting with epileptic encephalopathy, congenital microcephaly, global developmental delay, severe hypotonia, spasticity predominant at the lower limbs, and thin corpus callosum. Whole exome sequencing identified a novel segregating SLC1A4 gene homozygous mutation (c.1141G > A: p.Gly381Arg) as the likely cause of the disease in our family. In order to deeply characterize the electro-clinical and neurological phenotype in our index patient, long-term systematic video-electroencephalograms (EEG) as well as repeated brain imaging studies (which included tractographic reconstructions) were performed on a regular basis during a 7 years follow-up time. In conclusion, we suggest to carefully considering SLC1A4 biallelic mutations in individuals presenting an early onset severe neurodevelopmental disorder with variable spasticity and seizures, regardless the patients' ethnic background.