BACKGROUND: Succinic semialdehyde dehydrogenase deficiency (SSADHD) represents a model neurometabolic disease at the fulcrum of translational research within the Boston Children\'s Hospital Intellectual and Developmental Disabilities Research Centers (IDDRC), including the NIH-sponsored natural history study of clinical, neurophysiological, neuroimaging, and molecular markers, patient-derived induced pluripotent stem cells (iPSC) characterization, and development of a murine model for tightly regulated, cell-specific gene therapy.
METHODS: SSADHD subjects underwent clinical evaluations, neuropsychological assessments, biochemical quantification of γ-aminobutyrate (GABA) and related metabolites, electroencephalography (standard and high density), magnetoencephalography, transcranial magnetic stimulation, magnetic resonance imaging and spectroscopy, and genetic tests. This was parallel to laboratory molecular investigations of in vitro GABAergic neurons derived from induced human pluripotent stem cells (hiPSCs) of SSADHD subjects and biochemical analyses performed on a versatile murine model that uses an inducible and reversible rescue strategy allowing on-demand and cell-specific gene therapy.
RESULTS: The 62 SSADHD subjects [53% females, median (IQR) age of 9.6 (5.4-14.5) years] included in the study had a reported symptom onset at ∼ 6 months and were diagnosed at a median age of 4 years. Language developmental delays were more prominent than motor. Autism, epilepsy, movement disorders, sleep disturbances, and various psychiatric behaviors constituted the core of the disorder\'s clinical phenotype. Lower clinical severity scores, indicating worst severity, coincided with older age (R= -0.302, p = 0.03), as well as age-adjusted lower values of plasma γ-aminobutyrate (GABA) (R = 0.337, p = 0.02) and γ-hydroxybutyrate (GHB) (R = 0.360, p = 0.05). While epilepsy and psychiatric behaviors increase in severity with age, communication abilities and motor function tend to improve. iPSCs, which were differentiated into GABAergic neurons, represent the first in vitro neuronal model of SSADHD and express the neuronal marker microtubule-associated protein 2 (MAP2), as well as GABA. GABA-metabolism in induced GABAergic neurons could be reversed using CRISPR correction of the pathogenic variants or mRNA transfection and SSADHD iPSCs were associated with excessive glutamatergic activity and related synaptic excitation.
CONCLUSIONS: Findings from the SSADHD Natural History Study converge with iPSC and animal model work focused on a common disorder within our IDDRC, deepening our knowledge of the pathophysiology and longitudinal clinical course of a complex neurodevelopmental disorder. This further enables the identification of biomarkers and changes throughout development that will be essential for upcoming targeted trials of enzyme replacement and gene therapy.

We examined safety, tolerability, and efficacy of SGS-742, a γ-aminobutyric acid B (GABA-B) receptor antagonist, in patients with succinic semialdehyde dehydrogenase deficiency. This was a single-center randomized, double-blind crossover phase II clinical trial of SGS-742 versus placebo in patients with succinic semialdehyde dehydrogenase deficiency. Procedures included transcranial magnetic stimulation and the Adaptive Behavior Assessment Scale. Nineteen subjects were consented and enrolled; the mean age was 14.0 ± 7.5 years and 11 (58%) were female. We did not find a significant effect of SGS-742 on the Adaptive Behavior Assessment Scale score, motor threshold, and paired-pulse stimulation. The difference in recruitment curve slopes between treatment groups was 0.003 (P = .09). There was no significant difference in incidence of adverse effects between drug and placebo arms. SGS-742 failed to produce improved cognition and normalization of cortical excitability as measured by the Adaptive Behavior Assessment Scale and transcranial magnetic stimulation. Our data do not support the current use of SGS-742 in succinic semialdehyde dehydrogenase deficiency.Trial registry number NCT02019667. Phase 2 Clinical Trial of SGS-742 Therapy in Succinic Semialdehyde Dehydrogenase Deficiency. https://clinicaltrials.gov/ct2/show/NCT02019667.

Gamma-hydroxybutyric acid (GHB) acts as an agonist of the GABAB receptor, where GHB induces a depressant effect in the central nervous system. Besides its therapeutic application, GHB is also used as a date rape drug. However, the detection of GHB ingestion proves to be difficult due to its narrow detection window. The aim of this pilot study was to assess differential gene expressions after GHB intake to identify potential biomarkers for the detection of GHB intake. To this aim, alteration in gene expression of ALDH5A1, AKR7A2, EREG, and PEA15 was investigated via quantitative PCR (qPCR). Data normalization was based on a previously established and empirically derived normalization strategy. Blood samples of patients (n = 3) therapeutically taking sodium oxybate solution (GHB) and of donors without GHB intake (n = 49) were analyzed and compared. All qPCR procedures and results are reported according to the MIQE guidelines. Investigation of suitable reference genes using established algorithms suggested PPIB and FPGS as best-suited normalizers. Alterations in gene expression relating to GHB intake could not be confirmed to a forensically sufficient degree. However, significant differences in expression of EREG in the control group were observed, when time-point of sample collection was considered, indicating circadian rhythm. The study\'s main limitation is the small number of study subjects. Herein, we are first to present an empirically derived strategy for a robust normalization of qPCR data from the analysis of GHB-induced gene expression in human blood. We present results of the analysis of differential expression of ALDH5A1, AKR7A2, EREG, and PEA15 in the GHB-negative population. Finally, we report our findings on the effect of GHB intake on the expression of these genes and their presumable potential as GHB biomarkers.

OBJECTIVE: The present study highlights the feasibility of gas chromatography/mass spectrometry (GC/MS)-based analysis for simultaneous detection of >200 marker metabolites in urine found in characteristic pattern in inborn errors of metabolism (IEM) in India.
METHODS: During this retrospective study conducted from July 2013 to January 2016, we collected urine specimens on filter papers from Indian children across the country along with relevant demographic and clinical data. The laboratory technique involved urease pretreatment followed by deproteinization, derivatization, and subsequent computer-aided analysis of organic acids, amino acids, fatty acids, and sugars by GC/MS, which enable chemical diagnosis of IEM.
RESULTS: Totally 23,140 patients were investigated for IEM with an estimated frequency of about 1.40%, that is, 323 positive cases. Most frequent disorders observed were of primary lactic acidemia (27.2%) and organic acidemia (methylmalonic aciduria, glutaric acidemia type I, propionic aciduria, etc.) followed by aminoacidopathies (maple syrup urine disease, phenylketonuria, tyrosinemia, etc.). Furthermore, alkaptonuria, canavan disease, and 4-hydroxybutyric aciduria were also diagnosed. Prompt treatment following diagnosis led to a better outcome in a considerable number of patients.
CONCLUSIONS: GC/MS with one-step metabolomics enables quick detection, accurate identification, and precise quantification of a wide range of urinary markers that may not be discovered using existing newborn screening programs. The technique is effective as a second-tier test to other established screening technologies, as well as one-step primary screening tool for a wide spectrum of IEM.

OBJECTIVE: The objective of this open-label study was primarily to assess the effect of taurine on adaptive behavior and secondarily to collect safety and tolerability data in patients with succinic semialdehyde dehydrogenase deficiency.
METHODS: In the current study, subjects were titrated weekly from a starting dose of 50 mg/kg/d to a target 200 mg/kg/d, and assessed for safety, tolerability, and adaptive functioning using age-normalized Adaptive Behavior Assessment Scales.
RESULTS: Eighteen patients (8 males/10 females, aged 0.5-28 years, mean 12 years) were recruited. Three subjects withdrew because of perceived lack of efficacy. One serious adverse event occurred (hospitalization for hypersomnia) on 16 g/d (200 mg/kg/d), leading to a dose-lowering paradigm with a maximum dose of 10 g/d. Results did not show clinically meaningful improvement in the adaptive domains after taurine therapy. Pre- and posttherapy adaptive scores also demonstrated no statistically significant difference (p > 0.18).
CONCLUSIONS: Adaptive behavior did not improve significantly with taurine intervention. Further therapeutic clinical trials including an on-off paradigm using biomarkers are planned.
METHODS: This study provides Class IV evidence that for patients with succinic semialdehyde dehydrogenase deficiency, taurine does not significantly improve adaptive behavior. The study is rated Class IV because of the absence of a control group.

BACKGROUND: The Epilepsy Genetics (EPIGEN) Consortium was established to undertake genetic mapping analyses with augmented statistical power to detect variants that influence the development and treatment of common forms of epilepsy.
METHODS: We examined common variations across 279 prime candidate genes in 2717 case and 1118 control samples collected at four independent research centres (in the UK, Ireland, Finland, and Australia). Single nucleotide polymorphism (SNP) and combined set-association analyses were used to examine the contribution of genetic variation in the candidate genes to various forms of epilepsy.
RESULTS: We did not identify clear, indisputable common genetic risk factors that contribute to selected epilepsy subphenotypes across multiple populations. Nor did we identify risk factors for the general all-epilepsy phenotype. However, set-association analysis on the most significant p values, assessed under permutation, suggested the contribution of numerous SNPs to disease predisposition in an apparent population-specific manner. Variations in the genes KCNAB1, GABRR2, KCNMB4, SYN2, and ALDH5A1 were most notable.
CONCLUSIONS: The underlying genetic component to sporadic epilepsy is clearly complex. Results suggest that many SNPs contribute to disease predisposition in an apparently population-specific manner. However, subtle differences in phenotyping across cohorts, combined with a poor understanding of how the underlying genetic component to epilepsy aligns with current phenotypic classifications, might also account for apparent population-specific genetic risk factors. Variations across five genes warrant further study in independent cohorts to clarify the tentative association.

In the present paper we report the presence of succinic semialdehyde dehydrogenase (SSADH) in bovine adrenal medulla and blood platelets. Both enzymes present some analogies with the brain enzyme in terms of cofactor requirements, optimal pH, mitochondrial localizaton and inhibition by AMP. However, the activity of the platelet enzyme is 100 times lower than that of the brain and affinities of both enzymes for their specific substrate succinic semialdehyde and NAD are different. The presence of SSADH in adrenal medulla and blood platelets allows us to confirm the presence of a complete GABA bypass in these tissues, where the neurotransmitter could have important regulator functions.