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Phenylketonuria (PKU) is a rare metabolic disorder caused by mutations in the phenylalanine hydroxylase gene. Depending on the severity of the genetic mutation, medical treatment, and patient dietary management, elevated phenylalanine (Phe) may occur in blood and brain tissues. Research has recently shown that high Phe not only impacts the central nervous system, but also other organ systems (e.g., heart and microbiome). This study used ex vivo proton nuclear magnetic resonance (1H-NMR) analysis of urine samples from PKU patients (mean 14.9 ± 9.2 years, n = 51) to identify the impact of elevated blood Phe and PKU treatment on metabolic profiles. Our results found that 24 out of 98 urinary metabolites showed a significant difference (p < 0.05) for PKU patients compared to age-matched healthy controls (n = 51) based on an analysis of urinary metabolome. These altered urinary metabolites were related to Phe metabolism, dysbiosis, creatine synthesis or intake, the tricarboxylic acid (TCA) cycle, end products of nicotinamide-adenine dinucleotide degradation, and metabolites associated with a low Phe diet. There was an excellent correlation between the metabolome and genotype of PKU patients and healthy controls of 96.7% in a confusion matrix model. Metabolomic investigations may contribute to a better understanding of PKU pathophysiology.

The X-linked GRIA3 gene encodes the GLUA3 subunit of AMPA-type glutamate receptors. Pathogenic variants in this gene were previously reported in neurodevelopmental diseases, mostly in male patients but rarely in females. Here we report a de novo pathogenic missense variant in GRIA3 (c.1979G>C; p. R660T) identified in a 1-year-old female patient with severe epilepsy and global developmental delay. When exogenously expressed in human embryonic kidney (HEK) cells, GLUA3_R660T showed slower desensitization and deactivation kinetics compared to wildtype (wt) GLUA3 receptors. Substantial non-desensitized currents were observed with the mutant but not for wt GLUA3 with prolonged exposure to glutamate. When co-expressed with GLUA2, the decay kinetics were similarly slowed in GLUA2/A3_R660T with non-desensitized steady state currents. In cultured cerebellar granule neurons, miniature excitatory postsynaptic currents (mEPSCs) were significantly slower in R660T transfected cells than those expressing wt GLUA3. When overexpressed in hippocampal CA1 neurons by in utero electroporation, the evoked EPSCs and mEPSCs were slower in neurons expressing R660T mutant compared to those expressing wt GLUA3. Therefore our study provides functional evidence that a gain of function (GoF) variant in GRIA3 may cause epileptic encephalopathy and global developmental delay in a female subject by enhancing synaptic transmission.

22q11.2 deletion syndrome is the most common microdeletion syndrome. This article reviews the different neurological manifestations of 22q11.2 deletion syndrome. The syndrome is associated with neurological disorders such as epilepsy and movement disorders. Patients with 22q11.2 DS have an increased incidence of provoked and unprovoked seizures. Provoked seizures include, amongst others, seizures due to hypocalcemia, surgery, perioperative hypoxia, antipsychotic medication, and fever. Both focal seizures, myoclonus and generalized tonic–clonic seizures occur in 22q11.2 DS. Generalized epilepsy occurs more often than in the background population. Furthermore, 22q11.2 DS is associated with a significantly increased risk of developing Parkinson’s disease, and an increased incidence of dystonia has also been suggested. Abnormal neuroradiological findings — amongst them polymicrogyria — are common in 22q11.2.2 DS and reviewed in the article. The risk of psychiatric disorders, in particular schizophrenia, is increased in 22q11.2 DS.

O-linked β-N-acetylglucosamine (O-GlcNAc) transferase (OGT) is an essential enzyme that modifies proteins with O-GlcNAc. Inborn OGT genetic variants were recently shown to mediate a novel type of congenital disorder of glycosylation (OGT-CDG), which is characterised by X-linked intellectual disability (XLID) and developmental delay. Here, we report an OGTC921Y variant that co-segregates with XLID and epileptic seizures, and results in loss of catalytic activity. Colonies formed by mouse embryonic stem cells carrying OGTC921Y showed decreased levels of protein O-GlcNAcylation accompanied by decreased levels of Oct4 (encoded by Pou5f1), Sox2 and extracellular alkaline phosphatase (ALP), implying reduced self-renewal capacity. These data establish a link between OGT-CDG and embryonic stem cell self-renewal, providing a foundation for examining the developmental aetiology of this syndrome.

Purpose KBG syndrome (KBGS) is a rare neurodevelopmental syndrome. We aimed to study the impact of KBGS in adulthood as reported by individuals with KBGS and their families/caregivers, thereby exploring aspects of everyday life underreported by healthcare professionals. Methods We co‐produced an online questionnaire for adults with KBGS and their families/caregivers. Participants were recruited via the KBG Foundation, an American‐based charity supporting individuals with KBGS and their families worldwide, and other international collaborators. Results There were 91 responses for analysis, across the age range of 16–86 years. Respondents described a range of living arrangements, education, employment, leisure activities, and relationships. A higher proportion of 45–54year‐olds had achieved independent living skills such as driving and grocery shopping compared to the younger age groups. None of the participants who were experiencing seizures lived independently. We described high rates of psychiatric comorbidities, behavioral difficulties, sleep problems, seizures, visual and hearing problems, dental and skeletal issues, and a higher than expected cardiovascular and gastrointestinal burden of disease. Conclusion This study provides new insights into the everyday life of adults with KBGS, along with high rates of comorbidities that continue to impact quality of life into adulthood, with implications for medical care. KBG syndrome (KBGS) is one of the most common monogenic causes of ID alongside short stature, macrodontia, and other variable features. Phenotypes in childhood are well documented, but data are lacking about adulthood and how best to support individuals. This study provides essential data on the lived experience of KBGS in adulthood.

AGAP1 is an Arf1 GTPase-activating protein that regulates endolysosomal trafficking. Damaging variants have been linked to cerebral palsy and autism. We report three new cases in which individuals had microdeletion variants in AGAP1. The affected individuals had intellectual disability (3/3), autism (3/3), dystonia with axial hypotonia (1/3), abnormalities of brain maturation (1/3), growth impairment (2/3) and facial dysmorphism (2/3). We investigated mechanisms potentially underlying AGAP1 variant-mediated neurodevelopmental impairments using the Drosophila ortholog CenG1a. We discovered reduced axon terminal size, increased neuronal endosome abundance and elevated autophagy compared to those in controls. Given potential incomplete penetrance, we assessed gene–environment interactions. We found basal elevation in the phosphorylation of the integrated stress-response protein eIF2α (or eIF2A) and inability to further increase eIF2α phosphorylation with subsequent cytotoxic stressors. CenG1a-mutant flies had increased lethality from exposure to environmental insults. We propose a model wherein disruption of AGAP1 function impairs endolysosomal trafficking, chronically activating the integrated stress response and leaving AGAP1-deficient cells susceptible to a variety of second-hit cytotoxic stressors. This model may have broader applicability beyond AGAP1 in instances where both genetic and environmental insults co-occur in individuals with neurodevelopmental disorders.

GRIA3 at Xq25 encodes glutamate ionotropic receptor AMPA type 3 (GluA3), a subunit of postsynaptic glutamate-gated ion channels mediating neurotransmission. Hemizygous loss-of-function (LOF) variants in GRIA3 cause a neurodevelopmental disorder (NDD) in male individuals. Here, we report a gain-of-function (GOF) variant at GRIA3 in a male patient. We identified a hemizygous de novo missense variant in GRIA3 in a boy with an NDD: c.1844C > T (p.Ala615Val) using whole-exome sequencing. His neurological signs, such as hypertonia and hyperreflexia, were opposite to those in previous cases having LOF GRIA3 variants. His seizures and hypertonia were ameliorated by carbamazepine, inhibiting glutamate release from presynapses. Patch-clamp recordings showed that the human GluA3 mutant (p.Ala615Val) had slower desensitization and deactivation kinetics. A fly line expressing a human GluA3 mutant possessing our variant and the Lurcher variant, which makes ion channels leaky, showed developmental defects, while one expressing a mutant possessing either of them did not. Collectively, these results suggest that p.Ala615Val has GOF effects. GRIA3 GOF variants may cause an NDD phenotype distinctive from that of LOF variants, and drugs suppressing glutamatergic neurotransmission may ameliorate this phenotype. This study should help in refining the clinical management of GRIA3-related NDDs.

Neurofibromatosis type 1(NF1) is a dominantly inherited genetic disorder caused by a mutation in the NF1 tumor-suppressor gene. Patients are prone to develop benign and malignant tumors not only in the central and peripheral nervous system but also in other parts of the body. Apart from tumors, neurofibromatosis may also be associated with neurological symptoms and disorders such as cerebrovascular disease, epilepsy, neuropathy, and headache. This article seeks to review the different neurological manifestations of neurofibromatosis.

Purpose To provide a detailed electroclinical description and expand the phenotype of PIGT-CDG, to perform genotype–phenotype correlation, and to investigate the onset and severity of the epilepsy associated with the different genetic subtypes of this rare disorder. Furthermore, to use computer-assisted facial gestalt analysis in PIGT-CDG and to the compare findings with other glycosylphosphatidylinositol (GPI) anchor deficiencies. Methods We evaluated 13 children from eight unrelated families with homozygous or compound heterozygous pathogenic variants in PIGT . Results All patients had hypotonia, severe developmental delay, and epilepsy. Epilepsy onset ranged from first day of life to two years of age. Severity of the seizure disorder varied from treatable seizures to severe neonatal onset epileptic encephalopathies. The facial gestalt of patients resembled that of previously published PIGT patients as they were closest to the center of the PIGT cluster in the clinical face phenotype space and were distinguishable from other gene-specific phenotypes. Conclusion We expand our knowledge of PIGT . Our cases reaffirm that the use of genetic testing is essential for diagnosis in this group of disorders. Finally, we show that computer-assisted facial gestalt analysis accurately assigned PIGT cases to the multiple congenital anomalies–hypotonia–seizures syndrome phenotypic series advocating the additional use of next-generation phenotyping technology.