glutaryl-CoA Dehydrogenase Gene Research Articles

Compilation of Genotype and Phenotype Data in GCDH-LOVD for Variant Classification and Further Application.

Glutaric aciduria type 1 (GA-1) is a rare but treatable autosomal-recessive neurometabolic disorder of lysin metabolism caused by biallelic pathogenic variants in glutaryl-CoA dehydrogenase gene (GCDH) that lead to deficiency of GCDH protein. Without treatment, this enzyme defect causes a neurological phenotype characterized by movement disorder and cognitive impairment. Based on a comprehensive literature search, we established a large dataset of GCDH variants using the Leiden Open Variation Database (LOVD) to summarize the known genotypes and the clinical and biochemical phenotypes associated with GA-1. With these data, we developed a GCDH-specific variation classification framework based on American College of Medical Genetics and Genomics and the Association for Molecular Pathology guidelines. We used this framework to reclassify published variants and to describe their geographic distribution, both of which have practical implications for the molecular genetic diagnosis of GA-1. The freely available GCDH-specific LOVD dataset provides a basis for diagnostic laboratories and researchers to further optimize their knowledge and molecular diagnosis of this rare disease.

Biochemical and molecular features of chinese patients with glutaric acidemia type 1 from Fujian Province, southeastern China

BackgroundGlutaric acidemia type 1 (GA1) is a rare autosomal recessive inherited metabolic disorder caused by variants in the gene encoding the enzyme glutaryl-CoA dehydrogenase (GCDH). The estimated prevalence of GA1 and the mutational spectrum of the GCDH gene vary widely according to race and region. The aim of this study was to assess the acylcarnitine profiles and genetic characteristics of patients with GA1 in Fujian Province, southeastern China.ResultsFrom January 2014 to December 2022, a total of 1,151,069 newborns (631,016 males and 520,053 females) were screened using MS/MS in six newborn screening (NBS) centers in Fujian Province and recruited for this study. Through NBS, 18 newborns (13 females and 5 males) were diagnosed with GA1. Thus, the estimated incidence of GA1 was 1 in 63,948 newborns in Fujian province. In addition, 17 patients with GA1 were recruited after clinical diagnosis. All but one patient with GA1 had a remarkable increase in glutarylcarnitine (C5DC) concentrations. The results of urinary organic acid analyses in 33 patients showed that the concentration of glutaric acid (GA) increased in all patients. The levels of C5DC and GA in patients identified via NBS were higher than those in patients identified via clinical diagnosis (P < 0.05). A total of 71 variants of 70 alleles were detected in patients with GA1, with 19 different pathogenic variants identified. The three most prevalent variants represented 73.23% of the total and were c.1244-2 A > C, p.(?) (63.38%), c.1261G > A, p.Ala421Thr (5.63%), and c.406G > T, p.Gly136Cys (4.22%). The most abundant genotype observed was c.[1244-2 A > C]; [1244-2 A > C] (18/35, 52.43%) and its phenotype corresponded to high excretors (HE, GA > 100 mmol/mol Cr).ConclusionsIn conclusion, we investigated the biochemical and molecular features of 35 unrelated patients with GA1. C5DC concentrations in dried blood spots and urinary GA are effective indicators for a GA1 diagnosis. Our study also identified a GCDH variant spectrum in patients with GA1 from Fujian Province, southeastern China. Correlation analysis between genotypes and phenotypes provides preliminary and valuable information for genetic counseling and management.

Treatment of glutaric aciduria type I (GA-I) via intracerebroventricular delivery of GCDH

Glutaric aciduria type I (GA-I) is an autosomal recessive genetic disorder caused by a deficiency in glutaryl-CoA dehydrogenase (GCDH). Patients who do not receive proper treatment may die from acute encephalopathic crisis. Current treatments for GA-I include a low-lysine diet combined with oral supplementation of L-carnitine. A mouse model of Gcdhc.422_428del/c.422_428del (Gcdh−/−) was generated in our laboratory using CRISPR/Cas9. Gcdh−/− mice had significantly higher levels of glutaric acid (GA) in the plasma, liver, and brain than those in wild-type C57BL/6 mice. When given a high-protein diet (HPD) for two days, approximately 60% of Gcdh−/− mice did not survive the metabolic stress. To evaluate whether GCDH gene replacement therapy could be used to provide sustained treatment for patients with GA-1, we prepared a recombinant adeno-associated virus (rAAV) carrying a human GCDH expression cassette and injected it into Gcdh−/− neonates for a proof-of-concept (PoC) study. Our study demonstrated that delivering rAAV to the central nervous system (CNS), but not the peripheral system, significantly increased the survival rate under HPD exposure. Our study also demonstrated that rAAVPHP.eB mediated a higher efficiency than that of rAAV9 in increasing the survival rate. Surviving mice showed dose-dependent GCDH protein expression in the CNS and downregulation of GA levels. Our study demonstrated that AAV-based gene replacement therapy was effective for GA-I treatment and provided a feasible solution for this unmet medical need.

Biochemical, molecular, and clinical features of patients with glutaric acidemia type 1 identified through large-scale newborn screening in Zhejiang Province, China

BackgroundGlutaric acidemia type 1 (GA1) is a treatable neurometabolic disorder caused by biallelic variants in the glutaryl-CoA dehydrogenase (GCDH) gene. There are few large-scale reports describing newborn screening (NBS) for GA1 in China. We report the NBS results, genotypes, and clinical features of patients diagnosed through NBS. MethodsFrom January 2009 to August 2021, 4,202,587 newborns were screened by tandem mass spectrometry. Newborns with increased glutarylcarnitine (C5DC) concentrations were recalled for repeated test, and confirmatory examinations were performed if the second test was still positive. The pathogenicity of novel variants was predicted using computational programs. ResultsA total of 693 had increased C5DC concentrations, and 19 patients were diagnosed with GA1. Thus, the estimated incidence of GA1 in Zhejiang Province was 1 in 221,053 newborns. All the 19 patients had markedly increased C5DC concentrations and C5DC/octanoylcarnitine (C8) ratios; one had a slightly low free carnitine concentration. Seventeen (17/18, 94.4%) patients had increased GA concentrations, 15 were of high excretor phenotype and 3 were of low excretor phenotype. Twenty-three distinct GCDH variants were detected, of which 2were novel. Novel variants were predicted to be potentially pathogenic by computational programs. c.1244-2A > C was the most common variant, with an allelic frequency of 14.7%, followed by c.914C > T (p.S305L) (8.8%). The most common clinical symptom was movement disorder, followed by seizure, macrocephaly, and failure to thrive. Sylvian fissures widening was the most common MRI finding. ConclusionsNineteen GA1 patients were diagnosed through the large-scale NBS in Zhejiang Province, with an estimated incidence of 1 in 221,053 newborns. The GCDH mutational spectrum is heterogenous, with the c.1244-2A > C variant being the most frequent variant in this population. NBS for GA1 should be promoted to achieve timely diagnosis and treatment.

Biochemical and molecular features of Chinese patients with glutaric acidemia type 1 detected through newborn screening

BackgroundGlutaric acidemia type 1 (GA1) is a treatable disorder affecting cerebral organic acid metabolism caused by a defective glutaryl-CoA dehydrogenase (GCDH) gene. GA1 diagnosis reports following newborn screening (NBS) are scarce in the Chinese population. This study aimed to assess the acylcarnitine profiles and genetic characteristics of patients with GA1 identified through NBS.Results From January 2014 to September 2020, 517,484 newborns were screened by tandem mass spectrometry, 102 newborns with elevated glutarylcarnitine (C5DC) levels were called back. Thirteen patients were diagnosed with GA1, including 11 neonatal GA1 and two maternal GA1 patients. The incidence of GA1 in the Quanzhou region was estimated at 1 in 47,044 newborns. The initial NBS results showed that all but one of the patients had moderate to markedly increased C5DC levels. Notably, one neonatal patient with low free carnitine (C0) level suggest primary carnitine deficiency (PCD) but was ultimately diagnosed as GA1. Nine neonatal GA1 patients underwent urinary organic acid analyses: eight had elevated GA and 3HGA levels, and one was reported to be within the normal range. Ten distinct GCDH variants were identified. Eight were previously reported, and two were newly identified. In silico prediction tools and protein modeling analyses suggested that the newly identified variants were potentially pathogenic. The most common variant was c.1244-2 A>C, which had an allelic frequency of 54.55% (12/22), followed by c.1261G>A (p.Ala421Thr) at 9.09% (2/22).ConclusionsNeonatal GA1 patients with increased C5DC levels can be identified through NBS. Maternal GA1 patients can also be detected using NBS due to the low C0 levels in their infants. Few neonatal GA1 patients may have atypical acylcarnitine profiles that are easy to miss during NBS; therefore, multigene panel testing should be performed in newborns with low C0 levels. This study indicates that the GCDH variant spectra were heterogeneous in this southern Chinese cohort.

The outcome of 41 Late-Diagnosed Turkish GA-1 Patients: A Candidate for the Turkish NBS

Glutaric aciduria type 1(GA-1) is an inherited cerebral organic aciduria. Untreated patients with GA-1 have a risk of acute encephalopathic crises during the first 6 years of life. In so far as GA-1 desperately does not exist in Turkish newborn screening (NBS) program, most patients in our study were late-diagnosed. This study included 41 patients diagnosed with acylcarnitine profile, urinary organic acids, mutation analyses in the symptomatic period. We presented with clinical, neuroradiological, and molecular data of our 41 patients. The mean age at diagnosis was 14.8 ± 13.9 (15 days to 72 months) and, high blood glutaconic acid, glutarylcarnitine and urinary glutaric acid (GA) levels in 41 patients were revealed. Seventeen different mutations in the glutaryl-CoA dehydrogenase gene were identified, five of which were novel. The patients, most of whom were late-diagnosed, had a poor neurological outcome. Treatment strategies made a little improvement in dystonia and the frequency of encephalopathic attacks. All GA-1 patients in our study were severely affected since they were late-diagnosed, while others show that GA-1 is a treatable metabolic disorder if it is diagnosed with NBS. This study provides an essential perspective of the severe impact on GA-1 patients unless it is diagnosed with NBS. We immediately advocate GA-1 to be included in the Turkish NBS.

Molecular identification of glutaryl CoA dehydrogenase gene variations and clinical course in three glutaric aciduria type I patients

Glutaric aciduria type-I (GA-I) is a rare autosomal recessive organic-aciduria caused due to glutaryl-CoA-dehydrogenase (GCDH) gene mutations leading to the accumulation of neurotoxins. In this article, we describe the molecular study of three GA-I families from southern India. Clinical features and biochemical parameters were examined. DNA was isolated from dried blood spots and GCDH gene analysis was performed using polymerase chain reaction and Sangers sequencing. Computational assessment of the mutations was performed to analyse their pathogenicity. Median age of the patients was 8 months and parental consanguinity was seen in all the three families. All GA-I patients had a mild clinical course, with brain atrophies. Macrocephaly was not noted. Mutation analysis identified three likely pathogenic mutations including two novel GCDH gene variants (S189T and W225S) and one previously reported variant (R386P). In-silico tools determined R386P and W225S mutations to be deleterious, while S189T to be neutral to the GCDH protein. The S189T was associated with a low excretor phenotype. In conclusion, identification of mutations by genotyping tests in distinct populations can accomplish early DNA based GA-I screening and is useful in definitive diagnosis of GA-I without the prior need of biochemical or enzyme assay.

Molecular and biochemical study of glutaric aciduria type 1 in 49 Russian families: nine novel mutations in the GCDH gene.

Glutaric aciduria type 1 (GA1, deficiency of glutaryl CoA dehydrogenase, glutaric acidemia type 1) (ICD-10 code: E72.3; MIM 231670) is an autosomal recessive disease caused by mutations in the gene encoding the enzyme glutaryl CoA dehydrogenase (GCDH). Herein, we present the biochemical and molecular genetic characteristics of 51 patients diagnosed with GA1 from 49 unrelated families in Russia. We identified a total of 21 variants, 9 of which were novel: c.127 + 1G > T, с.471_473delCGA, c.161T > C (p.Leu54Pro), c.531C > A (р.Phe177Leu), c.647C > T (p.Ser216Leu), c.705G > A (р.Gly235Asp), c.898G > A (р.Gly300Ser), c.1205G > C (р.Arg402Pro), c.1178G > A (р.Gly393Glu). The most commonly detected missense variants were c.1204C > T (p.Arg402Trp) and с.1262C > T (р.Ala421Val), which were identified in 56.38% and 11.7% of mutated alleles. A heterozygous microdeletion of the short arm (p) of chromosome 19 from position 12,994,984-13,003,217 (8233 b.p.) and from position 12,991,506-13,003,217 (11,711 b.p.) were detected in two patients. Genes located in the area of imbalance were KLF1, DNASE2, and GCDH. Patients presented typical GA1 biochemical changes in the biological fluids, except one patient with the homozygous mutation p.Val400Met. No correlation was found between the GCDH genotype and glutaric acid (GA) concentration in the cohort of our patients.

A Low-Excretor Biochemical Phenotype of Glutaric Aciduria Type I: Identification of Novel Mutations in the Glutaryl CoA Dehydrogenase Gene and Review of Literature from India.

A Low-Excretor Biochemical Phenotype of Glutaric Aciduria Type I: Identification of Novel Mutations in the Glutaryl CoA Dehydrogenase Gene and Review of Literature from India.

Mutational analysis of glutaryl CoA dehydrogenase gene in glutaric aciduria type-I patients: A study from India

Mutational analysis of glutaryl CoA dehydrogenase gene in glutaric aciduria type-I patients: A study from India

Potential complementation effects of two disease-associated mutations in tetrameric glutaryl-CoA dehydrogenase is due to inter subunit stability-activity counterbalance

Glutaric Aciduria Type I (GA-I), is an autosomal recessive neurometabolic disease caused by mutations in the GCDH gene that encodes for glutaryl-CoA dehydrogenase (GCDH), a flavoprotein involved in the metabolism of tryptophan, lysine and hydroxylysine. Although over 200 disease mutations have been reported a clear correlation between genotype and phenotype has been difficult to establish. To contribute to a better molecular understanding of GA-I we undertook a detailed molecular study on two GCDH disease-related variants, GCDH-p.Arg227Pro and GCDH-p.Val400Met. Heterozygous patients harbouring these two mutations have increased residual enzymatic activity in relation to homozygous patients with only one of the mutations, suggesting a complementation effect between the two.Combining biochemical, biophysical and structural methods we here establish the effects of these mutations on protein folding, stability and catalytic activity. We show that both variants retain the overall protein fold, but with compromised enzymatic activities. Detailed enzyme kinetic studies reveal that GCDH-p.Arg227Pro has impaired function due to deficient substrate affinity as evidenced by its higher Km, and that the lower activity in GCDH-p.Val400Met results from weaker interactions with its physiological redox partner (electron transfer flavoprotein). Moreover, the GCDH-p.Val400Met variant has a significantly lower thermal stability (ΔTm ≈ 9 °C), and impaired binding of the FAD cofactor in relation to wild-type protein. On these grounds, we provide a rational for the possible interallelic complementation observed in heterozygous patients based on the fact that in GCDH, the low active p.Arg227Pro variant contributes to stabilize the tetramer while the structurally unstable p.Val400Met variant compensates for enzyme activity.

Is Expanded Newborn Screening Adequate to Detect Indian Biochemical Low Excretor Phenotype Patients of Glutaric Aciduria Type I?

To investigate if expanded newborn screening using tandem mass spectroscopy (TMS) is adequate to detect low excretor phenotype in Indian Glutaric aciduria type I (GA-I) patients. Ten GA-I patients were investigated for blood glutaryl carnitine (C5DC) levels on dried blood spot (DBS) by tandem mass spectroscopy and urine glutaric acid (GA) and 3-hydroxyglutaric acid (3-OH-GA) by gas chromatography-mass spectroscopy. The student's T test and Pearson's correlation were applied to draw a relationship between various biochemical parameters. Further confirmation of low excretors by DNA mutation analysis in the glutaryl CoA dehydrogenase (GCDH) gene was performed by polymerase chain reaction and Sangers sequencing. Among 10 GA-I patients, 7 patients were found to have high excretor, and 3 were found to have low excretor phenotype. The low excretors were found to have GCDH gene mutations. The mean C5DC levels in high and low excretors were 2.61 ± 2.02μmol/L and 2.31 ± 1.00μmol/L, respectively. In high excretors, C5DC levels correlated with GA (r = 0.95). In low excretors, C5DC levels correlated with 3-OH-GA (r = 0.99). No significant difference was found between C5DC levels of high and low excretors (p = 0.82). The MS/MS, C5DC screening is a sensitive technique and detected 10 GA-I patients. Irrespective of the urine organic acid levels, Indian GA-I patients including low excretors seem to have a significantly elevated C5DC level and well above the stipulated cut-off values and therefore, expanded newborn screening is probably adequate to diagnose them.

Clinical phenotype and novel mutation in one of twins with glutaric acidemia type I

To review the clinical features of a male twin affected with glutaric academia type I (GA-I) and analyze the variations of glutaryl-CoA dehydrogenase (GCDH) gene. Clinical data of the pair of twins and their parents were collected. Genomic DNA was extracted from peripheral blood samples, and variants of GCDH genes were detected by capture sequencing using a customized panel. Variants of the twins and their parents were verified by Sanger sequencing. The level of glutaric acyl carnitine (C5DC + C6OH) was 3.26 μmol/L in the male twin. The relative level of glutaric acid in urine was 547.51 by gas chromatography mass spectrometry analysis. Cerebral ultrasonography showed that the patient had subependymal hemorrhage, but no serious clinical manifestation was noted. After treating with special formula milk powder and L-carnitine, the boy showed good growth and development. Two heterozygous variants of the GCDH gene were detected in the patient, among which c.416C>G was suspected to be pathogenic, while c.109_110delCA was unreported. The variants were respectively inherited from his parents. The twin girl only carried the c.416C>G variant. GA-I can be diagnosed by mass spectrometry, urine gas chromatographic mass spectrometry, imaging as well as genetic diagnosis. Early diagnosis and intervention is important.

Clinical, biochemical, neuroradiological and molecular characterization of Egyptian patients with glutaric acidemia type 1

Glutaric acidemia type 1 (GA1) is an inherited metabolic autosomal recessive disorder that is caused by a deficiency in glutaryl-CoA dehydrogenase (GCDH). Untreated patients suffer primarily from severe striatal damage. More than 250 variants in the GCDH gene have been reported with a variable frequency among different ethnic groups. In this study, we aimed to characterize 89 Egyptian patients with GA1 and identify the variants in the 41 patients who were available for genotyping. All of our patients demonstrated clinical, neuroradiological, and biochemical characteristics that are consistent with a diagnosis of GA1. All patients presented with variable degrees of developmental delay ranging from mild to severe. Most of the 89 patients presented with acute onset type (71.9%), followed by insidious (19%) and asymptomatic (9%). A delay in diagnosis was inversely associated with macrocephaly. The prevalence rate ratio (PR) for macrocephaly that was associated with each 6-month delay was 0.95 (95%CI 0.91–0.99). However, high body weight was associated with a higher likelihood of having macrocephaly (PR 1.16, 95%CI 1.06–1.26 per 1 SD increment of Z score weight). However, body weight was inversely associated with the morbidity score. Consanguinity level was 64% among our patient’s cohort and was positively associated with the C5DC level (β (95%CI) 1.06 (0.12–1.99)). Forty-one patients were available for genotyping and were sequenced for the GCDH gene. We identified a total of 25 variants, of which the following six novel variants were identified: three missense variants, c.320G > T (p.Gly107Val), c.481C > T (p.Arg161Trp) and c.572 T > G (p.Met191Arg); two deletions, c.78delG (p.Ala27Argfs34) and c.1035delG (p.Gly346Alafs*11); and one indel, c.272_331del (p.Val91_Lys111delinsGlu). All of the novel variants were absent in the 300 normal chromosomes. The most common variant, c.*165A > G, was detected in 42 alleles, and the most commonly detected missense variant, c.1204C > T (p.Arg402Trp), was identified in 29 mutated alleles in 15/41 (34.2%) of patients. Our findings suggest that GA1 is not uncommon organic acidemia disease in Egypt; therefore, there is a need for supporting neonatal screening programs in Egypt.

Glutaric aciduria type 1: a review of phenotypic and genetic characteristics

Glutaric aciduria type I (GA1) is an inherited metabolic disorder in which excessive levels of the amino acids lysine, hydroxylysine, and tryptophan accumulate in the body as a result of defective glutaryl-CoA dehydrogenase (GCDH) enzyme activity. Excessive metabolites are toxic that can cause damage to the brain, particularly due to the occurrence of basal ganglia and intellectual disability. Missense, splicing, and other deletion mutations in GCDH gene lead to the deficiency of the enzyme activity and are known to cause GA1. The severity of GA1 along with its neurological manifestations and clinical outcome is dependent upon the age at onset and therefore, early definitive diagnosis of GA1 becomes essential. GA1 occurs in approximately 1 of every 30,000-40,000 individuals worldwide that may reach up to 1 in 300 newborn babies in the Amish and Canadian communities. Owing to very high consanguinity rates in Saudi Arabia, it is presumed to be much more common in the Kingdom and is one of the initial disorders that were included in the country's neonatal screening program. In the current study, we have reviewed clinical manifestations, diagnosis, updated management, and mutation spectrum in GA1 with an example of one of our patients with GA1, and highlighted the importance of multipara-metric strategy in the early diagnosis and management of the disease.

Clinical and variation analysis of three Chinese families affected with glutaric acidemia type 1

To detect potential variation in glutaryl-CoA dehydrogenase (GCDH) gene among three Chinese families affected with glutaric acidemia type Ⅰ(GA-1) and correlate the genotypes with phenotypes. Genomic DNA was extracted from peripheral blood samples derived from three patients with GA-1 and their family members. The coding regions of the GCDH gene were amplified with PCR and subjected to Sanger sequencing. The clinical manifestation of the patients varied from macrocephaly to severe encephalopathy, with notable phenotypic difference between siblings carrying the same variation. In pedigrees 1 and 2, the probands have carried compound heterozygous variations c.1133C>T(p.Ala378Val) and c.1244-2A>C, which were derived their fathers and mothers, respectively. In pedigree 3, the proband has carried compound heterozygous variation c.339delT (p.Tyr113) and c.406G>T (p.Gly136Cys). Among these, variations c.339delT and c.1133C>T were verified as novel by retrieval of dsSNP, HGMD and 1000 genome database. Bioinformatic analysis suggested that above variations can affect protein function and are probably pathogenic. Above discovery has expanded the mutation spectrum of the GCDH gene. No correlation was found between the clinical phenotype and genotype of GA-1 patients.

Molecular genetic study of glutaric aciduria, type I: Identification of a novel mutation

Glutaric acidemia type I (GA-1) is an inborn error of metabolism due to deficiency of glutaryl-CoA dehydrogenase (GCDH), which catalyzes the conversion of glutaryl-CoA to crotonyl-CoA. GA-1 occurs in about 1 in 100 000 infants worldwide. The GCDH gene is on human chromosome 19p13.2, spans about 7 kb and comprises 11 exons and 10 introns. Tandem mass spectrometry (MS/MS) was used for clinical diagnosis in a proband from Iran with GA-1. Sanger sequencing was performed using primers specific for coding exons and exon-intron flanking regions of the GCDH gene in the proband. Cosegregation analysis and in silico assessment were performed to confirm the pathogenicity of the candidate variant. A novel homozygous missense variant c.1147C > A (p.Arg383Ser) in exon 11 of GCDH was identified. Examination of variant through in silico software tools determines its deleterious effect on protein in terms of function and stability. The variant cosegregates with the disease in family. In this study, the clinical and molecular aspects of GA-1 were investigated, which showed one novel mutation in the GCDH gene in an Iranian patient. The variant is categorized as pathogenic according to the the guideline of the American College of Medical Genetics and Genomics (ACMG) for variant interpretation. This mutation c.1147C > A (p.Arg383Ser) may also be prevalent among Iranian populations.

Genetic Screening of Selected Disease-Causing Mutations in Glutaryl-CoA Dehydrogenase Gene among Indian Patients with Glutaric Aciduria Type I.

Glutaric aciduria type I (GA-I) is an organic aciduria caused by glutaryl-CoA dehydrogenase (GCDH) deficiency. There are limited studies on GA-I from India. A total of 48 Indian GA-I patients were screened for selected disease-causing mutations such as R402W, A421V, A293T, R227P, and V400M using polymerase chain reaction (PCR) and restriction fragment length polymorphism (RFLP). Among these patients, 9 (18.8%) had R402W mutation, and none had A421V, A293T, R227P, or V400M mutation. One low excretor mutation (P286S) and several novel mutations (I152M, Q144P, and E414X) were also found in this study. We conclude that among selected mutations, R402W is the most common mutation found among Indian GA-I patients.

Disease-causing mutations affecting surface residues of mitochondrial glutaryl-CoA dehydrogenase impair stability, heteromeric complex formation and mitochondria architecture.

The neurometabolic disorder glutaric aciduria type 1 (GA1) is caused by mutations in the GCDH gene encoding the mitochondrial matrix protein glutaryl-CoA dehydrogenase (GCDH), which forms homo- and heteromeric complexes. Twenty percent of all pathogenic mutations affect single amino acid residues on the surface of GCDH resulting in a severe clinical phenotype. We report here on heterologous expression studies of 18 missense mutations identified in GA1 patients affecting surface amino acids. Western blot and pulse chase experiments revealed that the stability of half of the GCDH mutants was significantly reduced. In silico analyses showed that none of the mutations impaired the 3D structure of GCDH. Immunofluorescence co-localisation studies in HeLa cells demonstrated that all GCDH mutants were correctly translocated into mitochondria. Surprisingly, the expression of p.Arg88Cys GCDH as well as further substitutions by alanine, lysine, or methionine but not histidine or leucine resulted in the disruption of mitochondrial architecture forming longitudinal structures composed of stacks of cristae and partial loss of the outer mitochondrial membrane. The expression of mitochondrial fusion or fission proteins was not affected in these cells. Bioluminescence resonance energy transfer analyses revealed that all GCDH mutants exhibit an increased binding affinity to electron transfer flavoprotein beta, whereas only p.Tyr155His GCDH showed a reduced interaction with dihydrolipoamide succinyl transferase. Our data underscore the impact of GCDH protein interactions mediated by amino acid residues on the surface of GCDH required for proper enzymatic activity.

Glutaric AciduriaType 1: Clinical and Molecular Study in Iranian Patients, 3 Novel Mutations.

Glutaricaciduria type 1 (GA1), is a rare, treatable neuro metabolic disease, due to glutaryl- CoA dehydrogenase (GCDH) gene mutation.In regions without neonatal blood screening (NBS), patients are diagnosed in symptomatic period. This study was carried out to assess patients with GA1 for clinical, biochemical, neuroimaging findings and GCDH gene mutations analysis. In this cross-sectional study, clinical manifestation, neuroimaging and metabolic findings of eleven Iranian GA1 patients of MofidChildren's Hospital, Tehran, Iranbetween 2001 and 2011,were evaluated.Mutational analysis of the GCDH gene was performed on genomic DNA. Genomic DNA was extracted from peripheral lymphocytes using QIAamp DNA Micro Kit (Qiagen). All 11 exons and flanking intronic regions of the GCDH gene were amplified by polymerase chain reaction (PCR). All patients were diagnosed before 32 months old. Clinical presentations of GA1 include acute encephalopathic crisis and/or developmental delay and macrocephaly. Seven GCDH gene mutations were detected in our patients. The most frequent GCDH mutations occurred in exon7 then exon8, 10 and11. G244 C in exon7, R294 Q in exon8 and N373 S in exon 10 were three novel mutations. There was no correlation between of genotype and phenotype in our patients. Physician must remember GA1 in differential diagnosis of acute encephalopathic crisis, macrocephaly, developmental delay, movement disorders such as dystonia and dyskinesia. Early detection, proper treatment and selective screening of patients' siblings can prevent neurologic disabilities.