Molecular genetics and metabolism最新文献

Mucopolysaccharidosis type II (MPS II), also known as Hunter syndrome, is an X-linked lysosomal storage disorder. It results from a deficiency of the enzyme iduronate-2-sulfatase (I2S), leading to the accumulation of glycosaminoglycans (GAGs) in various tissues and organs. Clinical manifestations include skeletal abnormalities, facial coarsening, organ enlargement, and developmental delays. The main objective of this study was to identify neuronopathic MPS II-specific biomarkers for early detection, diagnosis, monitoring, and follow up of affected patients. We thus applied liquid chromatography-high-resolution mass spectrometry (LC-HRMS) based untargeted metabolomic approaches to identify these potential biomarkers which could discriminate patients with the neuronopathic form of MPS II from healthy controls. Secondary aims focused on a better understanding of how the disease may affect the metabolome of patients. Urine and plasma samples from 21 untreated neuronopathic MPS II patients characterized by severe clinical manifestations were compared to 23 age- and gender-matched healthy control samples using a Xevo G2-XS Qtof MS (Waters Corp.). A comprehensive metabolomic workflow and multivariate statistical analyses revealed metabolites consistently elevated in MPS II patients. These include acylaminosugars, dipeptides, amino acids and their derivatives, lipid structures, and various compounds indicating disruptions in metabolic pathways. Development and validation of quantitative methods will be done using tandem mass spectrometry. Furthermore, identifying biomarkers associated with the central nervous system (CNS) in MPS II patients would help detect the neuronopathic form of the disease early, and enable the evaluation of the effectiveness of novel therapeutic strategies.

The detection of antidrug antibodies (ADAs) is important for monitoring patients with Fabry disease who are undergoing enzyme replacement therapy (ERT) with recombinant α-galactosidase A (GLA) drugs, as ADAs can cause allergic reactions and reduce therapeutic efficacy. Various immunological methods, particularly enzyme-linked immunosorbent assay (ELISA), are widely used to measure serum ADA titers in patients with Fabry disease. However, estimating and comparing results of ELISA is challenging because of the absence of a reference antibody. In this study, we developed a genetically engineered chimeric immunoglobulin G monoclonal antibody with mouse-derived variable regions that can react with recombinant GLA drugs and human constant regions that are necessary for recognition by the enzyme-conjugated antihuman signal antibody. Using this chimeric antibody as a reference, a new ELISA-based test was designed to measure anti-GLA antibody concentrations in serum samples. After validating the method, serum anti-GLA antibody titers were measured in 31 patients with Fabry disease, and three representative patients were monitored for 36 months after ERT initiation, achieving successful results, particularly in patients with high ADA titers.

Mitochondrial 3-hydroxy-3-methylglutaryl-CoA synthase 2 (HMGCS2) deficiency is a rare, potentially life-threatening autosomal recessive disorder resulting from mutations in the HMGCS2 gene, leading to impaired ketogenesis. We systematically reviewed the clinical presentations, biochemical and genetic abnormalities in 93 reported cases and 2 new patients diagnosed based on biochemical findings. Reported onset ages ranged from 3 months to 6 years, mostly before the age of 3. Children younger than one year old are more prone to a severe clinical course. In most patients, the initial metabolic decompensation occurs after an episode of gastroenteritis or gastroenteritis-like symptoms. Other commonly observed symptoms during the first clinical episode included poor intake, altered consciousness, dyspnea, seizures and hepatomegaly. Severity was correlated with the number of truncating mutations. Most patients presented with acute metabolic decompensation with hypoglycemia, dicarboxyluria and inadequate ketonuria. Dicarboxylic acid levels were elevated in 54/56 cases. The organic acid 4-hydroxy-6-methyl-2-pyrone (4HMP) was detected in 33/35 urine samples taken during the acute episodes, but typically only retrospectively. The plasma C2/C0 acylcarnitine ratio was abnormal in 16/18 (88.9 %) of acute plasma samples, but only in 2/6 (33 %) of DBS samples. Other metabolites that have been reported are hydroxyhexenoic acid, 3,5-dihydroxyhexanoic (1,5 lactone), glutaric acidand 3-OH-isovaleric acid. Laboratories should look for 4HMP in urinary organic acid analysis and an increased plasma C2/C0 acylcarnitine ratio to facilitate the diagnosis of HMGCS2 deficiency, especially in cases of metabolic decompensation with dicarboxyluria without adequate ketonuria.

Dysmorphisms, or physical abnormalities in appearance, can vary in frequency and severity among individuals with inherited metabolic disorders (IMD). The prevalence of dysmorphisms in these disorders can range from rare occurrences to more common features, depending on the specific disorder and its genetic characteristics. It is important to note that not all individuals with IMDs will exhibit dysmorphic features, and the presence of such features may vary widely among different types of metabolic disorders. The data presented in this study, which includes a detailed list of 374 IMDs with dysmorphic characteristics categorized by affected organs (such as head and face, nose, mouth and tongue, eye, ear, hands and feet, and others), as well as an overview of important clinical features and recommended diagnostic strategies, could be valuable for professionals in the field of healthcare. This information may be particularly useful for healthcare providers who treat individuals with metabolic disorders or those who care for individuals exhibiting dysmorphic features that could indicate the presence of an inherited metabolic disorder.

GNE myopathy is a rare genetic muscle disorder characterized by initial ankle dorsiflexor weakness and the presence of rimmed vacuoles in muscle histopathology. Biallelic mutations in the GNE gene are causative, leading to reduced production of sialic acid. In our previous clinical trial, we used 6'-sialyllactose (6SL) as a supplement to increase sialic acid levels and compared the effects of 6SL at doses of 3 g and 6 g. The findings from the trial revealed superior outcomes in muscle strength, attenuation of muscle degeneration, and bioavailability in the 6 g group. This trial was planned to complement the lack of placebo arm from the previous trial and to provide more conclusive evidence for therapeutic value of 6SL in GNE myopathy. Of the 11 participants, five were allocated to the 6SL and six to the placebo group after undergoing 12 weeks of pre-study observation and stratified randomization. At every visit with an interval of 12 weeks for 48 weeks, all participants underwent muscle strength measurement, muscle MRI, biochemical evaluations, 6-min-walk test, and completed a questionnaire. No safety concerns arose during the trial period. Muscle strength, excluding hand grip power, did not show a significant difference between the two groups, which is attributed to the lack of pronounced muscle strength decline in both groups. Hand grip power tended to decrease in both groups, and this decline was statistically significant in the placebo group (p = 0.0004). The fat fraction measured by MRI showed the most significant results in the posterior thigh. The increase in fat fraction, indicating muscle degeneration, was statistically significant between the two groups (p = 0.0004). Although no statistically significant differences were observed between the groups in anterior thigh and both anterior and posterior lower leg, a trend of slowed increase in fat fraction was noted in the 6SL group compared to the placebo group starting from 24 or 36 weeks. Resialylation of cell surface glycoconjugate was demonstrated in 6SL group by measuring lectin bindings on peripheral blood monocytes. The GNEM-FAS, used to assess patient-reported outcomes, did not show statistical significance in the total score or any of the three domains. However, the tendency for scores in the self-care and upper extremity domains to rebound after 24 weeks in the 6SL group suggests the potential for long-term benefits. The effect of 6SL on muscle strength appeared to be minimal compared to our previous clinical trial, likely due to the short duration of the study and the inclusion of relatively early-stage patients. However, the changes in fat fraction measured by muscle MRI and the results of biochemical assays are more promising, suggesting potential benefits with long-term administration in the future.

Background: Pyridoxine-dependent epilepsy (PDE-ALDH7A1) is a developmental epileptic encephalopathy historically characterized by seizures that are resistant to antiseizure medications. Treatment with pyridoxine and lysine reduction therapies are associated with seizure control and improved developmental outcomes. In rare circumstances, patients have died prior to diagnosis and treatment with pyridoxine, and many patients are diagnosed after six months of age when lysine reduction therapies have limited efficacy. Recently two new metabolites were identified (2S,6S-/2S,6R-oxopropylpiperidine-2-carboxylic acid, 2-OPP and 6-oxo-pipecolate, 6-oxo-pip), and we evaluated these metabolites as potential newborn screening biomarkers.

Methods: We recruited participants with a confirmed diagnosis of PDE-ALDH7A1 and retrieved their residual dried blood spots from state-sponsored newborn screening programs. We evaluated the dried blood spots for 2-OPP using commercially available newborn screening kits and equipment, and developed a second-tier test for 6-oxo-pip using LC-MS/MS.

Results: We received eight residual dried blood spots collected before the onset of seizures and the diagnosis of PDE-ALDH7A1. In our newborn screening experiments, 2-OPP was elevated in 7 of 8 samples from affected participants with a mean of 3.08 μmol/L (95 % CI 2.17-3.99) compared to a mean of 0.09 μmol/L (95 % CI 0.09-0.10) in controls (p < 0.001). Second tier testing demonstrated elevated 6-oxo-pip in all samples from affected participants with a mean of 5.66 μmol/L (95 % CI 1.51-9.81) and was undetectable in controls (p < 0.001).

Conclusion: Patients with PDE-ALDH7A1 can be identified using neonatal dried blood spots prior to the onset of symptoms. The use of commercially available newborn screening approaches demonstrates the feasibility of newborn screening for this treatable condition.

Free sialic acid storage disorder (FSASD) is a rare autosomal recessive lysosomal storage disease caused by pathogenic SLC17A5 variants with variable disease severity. We performed a multidisciplinary evaluation of an adolescent female with suspected lysosomal storage disease and conducted comprehensive studies to uncover the molecular etiology. The proband exhibited intellectual disability, a storage disease gestalt, and mildly elevated urine free sialic acid levels. Skin electron micrographs showed prominent cytoplasmic vacuolation. Clinical exome and genome sequencing identified a maternally-inherited SLC17A5 variant: c.533delC;p.Thr178Asnfs*34. RNASeq of proband skin fibroblasts revealed exon 3 skipping, which was not detected in RNA from proband blood or parental fibroblasts. Targeted deep sequencing of proband fibroblast DNA revealed a 184 bp deletion in ∼15 % of reads, encompassing the 3' end of exon 3. Illumina Complete Long Read sequencing confirmed the deletion was in the paternally-inherited allele and found in a mosaic state in proband fibroblasts and muscle but not in blood or buccal cells. Functional studies, including SLC17A5 knockout cells and transient transfections of mutated SLC17A5 demonstrated pathogenicity of the identified variants. We report an adolescent female with atypical FSASD with tissue-specific mosaicism for an intragenic deletion in SLC17A5, explaining the atypical clinical course, mild biochemical abnormalities, and long diagnostic process.

Though it has no catalytic activity toward GM2 ganglioside, the GM2 activator protein (GM2A) is essential for ganglioside hydrolysis by facilitating the action of lysosomal ß-N-acetylhexosaminidase. GM2A deficiency results in death in early childhood due to rapid central nervous system deterioration similar to the related GM2 gangliosidoses, Tay-Sachs disease and Sandhoff disease. This manuscript further characterizes a feline model of GM2A deficiency with a focus on clinical and biochemical parameters that may be useful as benchmarks for translational therapeutic research. The GM2A deficient cat has clinical features consistent with the human condition, including isointensity of gray and white matter of the brain on T2-weighted MRI; MR spectroscopic changes of brain metabolites consistent with gliosis, neuronal injury and demyelination; rhythmical slowing of cerebral cortical activation on electroencephalography; and elevation of aspartate aminotransferase and lactate dehydrogenase in cerebrospinal fluid. Biochemically, the brain of GM2A deficient cats has storage of GM2 and GA2 ganglioside coincident with increased hexosaminidase activity toward a standard synthetic substrate. Also, the brain of GM2A deficient cats has increased levels of lyso-platelet activating factor and lyso-phosphatidylcholine, which may serve as novel biomarkers of disease progression and provide insights into pathogenic mechanisms.