Lyase Deficiency Research Articles

Biochemical and structural analysis of 14 mutant adsl enzyme complexes and correlation to phenotypic heterogeneity of adenylosuccinate lyase deficiency

Adenylosuccinate lyase (ADSL) deficiency is neurometabolic disease characterized by accumulation of dephosphorylated enzyme substrates SAICA-riboside (SAICAr) and succinyladenosine (S-Ado) in body fluids of affected individuals. The phenotypic severity differs considerably among patients: neonatal fatal, severe childhood, and moderate phenotypic forms correlating with different values for the ratio between S-Ado and SAICAr concentrations in cerebrospinal fluid have been distinguished. To reveal the biochemical and structural basis for this phenotypic heterogeneity, we expressed and characterized 19 ADSL mutant proteins identified in 16 patients representing clinically distinct subgroups. Respecting compound heterozygosity and considering the homotetrameric structure of ADSL, we used intersubunit complementation and prepared and characterized genotype-specific heteromeric mutant ADSL complexes. We correlated clinical phenotypes with biochemical properties of the mutant proteins and predicted structural impacts of the mutations. We found that phenotypic severity in ADSL deficiency is correlated with residual enzymatic activity and structural stability of the corresponding mutant ADSL complexes and does not seem to result from genotype-specific disproportional catalytic activities toward one of the enzyme substrates. This suggests that the S-Ado/SAICAr ratio is probably not predictive of phenotype severity; rather, it may be secondary to the degree of the patient's development (i.e., to the age of the patient at the time of sample collection).

Study of inborn errors of metabolism in urine from patients with unexplained mental retardation

Mental retardation (MR) is a common disorder frequently of unknown origin. Because there are few studies regarding MR and inborn errors of metabolism (IEM), we aimed to identify patients with IEM from a cohort of 944 patients with unexplained MR. Biochemical examinations such as determination of creatine (Cr) metabolites, acylcarnitines, purine, and pyrimidines in urine were applied. We found seven patients with IEM [three with cerebral Cr deficiency syndromes (CCDS)], one with adenylosuccinate lyase (ADSL) deficiency, and three, born before the neonatal metabolic screening program in Catalonia, with phenylketonuria (PKU). All told, they represent 0.8% of the whole cohort. All of them had additional symptoms such as epilepsy, movement disorders, autism, and other psychiatric disturbances. In conclusion, in patients with MR, it is essential to perform a thorough appraisal of the associated signs and symptoms, and in most disorders, it is necessary to apply specific analyses. In some cases, it is important to achieve an early diagnosis and therapy, which may reduce the morbimortality, and to offer genetic counselling.

Clinical and biochemical characteristics of patients with urea cycle disorders in a developing country

Objectives To report the clinical and laboratory characteristics of urea cycle disorder (UCD) patients at a tertiary care center in a developing country. Design and methods Retrospective study of clinical and laboratory data of UCD patients. Results Thirty-seven UCD patients were studied, 31 symptomatic (high risk) patients (15 neonatal onset, 16 late onset) and 6 with positive neonatal screening. Argininosuccinate synthetase deficiency was the most frequent disease (17/37, 46%), followed by ornithine transcarbamylase (10/37, 27%), arginase (7/37, 19%), and argininosuccinate lyase (3/37, 8%) deficiencies. Mortality of symptomatic patients was 38% (10/26), neonatal onset had the worst outcome, with 50% of survival. Conclusions In Mexico, the mortality of the UCD patients is higher than those reported in other countries, and neurological sequels are frequent and severe. It is essential to implement practice guidelines for the professional management of these patients.

Déficit en 3-HMG-CoA lyase à révélation tardive : savoir reconnaître une maladie rare mais traitable

3-Hydroxy-3-methylglutaric aciduria is a rare autosomal recessive genetic disorder due to a deficiency of the 3-hydroxy-3-methylglutarylCoA lyase (HMG-CoA lyase), a mitochondrial enzyme involved in ketogenesis and in the final step of l-leucine catabolism. HMG-CoA lyase deficiency can lead, in particular circumstances, such as fever, prolonged fasting or digestive disorders, to brutal and severe hypoglycemia with metabolic acidosis and sometimes fatal coma. We report on a new case of 3-hydroxy-3-methylglutaric aciduria particular by its late onset in a 3-year-old patient. Molecular investigation identified two new sequence modifications in the HMGCL gene: c.494G>A (p.Arg165Gln) and c.820G>A (p.Gly274Arg). We remind about this case report that the therapeutical is mainly preventive and allows a very good prognosis for this disease. Long-term treatment consists in limited fasting time, continuous low protein diet and l-carnitine supplementation. Preventive measures are essential: prevention of fasting and emergency treatment during intercurrent infections.

한국재래닭의 ADSL 유전자 내 단일염기변이를 이용한 경제형질과의 연관성 분석

Adenylosuccinate lyase (ADSL) deficiency is a disease of purine metabolism which affects patients both bioche- micall and behaviorally. An obstacle of this purine nucleotide cycle(PNC) can be caused brain functional disorder and growth disorder. So ADSL deficiency, which is associated with sever mental retardation, autistic features and energy metabolism. This study was performed to identify SNP on ADSL gene in chicken. The nucleotides were observed as T to C (7724 th nucleotide), C to T nd nucleotide), G to T (10108 th nucleotide), A to T (10356 th nucleotide), G to A(10375 th nucleotide), A to C (10402 nd nucleotide), A to T (12716 th nucleotide), T to A (12717 th nucleotide), C to T (15491 st nucleotide), C to T (15542 nd nucleotide) and C to T (15550 th nucleotide). The nucleotide substitutions at 15542 nd and 15550 th (GeneBank accession no. AY665559) were found as missense mutation (alanine valine, proline serine, respectively). This study will be useful for farther researches for identi- fying association between these SNPs and energy metabolism in chicken. The C15550T SNP showed three genotypes, CC, CT, TT by digestion with the genotype TT had significantly faster the first lay day (150.0) than CT (162.0, P<0.05) and genotype TT (150.0, P<0.05) had significantly higher the egg production rate than CT (172.4, P<0.05). According to result of this study, a C15550T was found to have a significantly effect first lay day and mean egg production. It will be possible to use SNP marker on selecting chicken to improve important economic traits, which is the first lay day and mean egg production.

Twins with KBG Syndrome and Autism

Twins with KBG Syndrome and Autism

Argininosuccinate lyase deficiency: Longterm outcome of 13 patients detected by newborn screening

Argininosuccinate lyase deficiency is a urea cycle disorder which can present in the neonatal period with hyperammonemic encephalopathy, or later in childhood with episodic vomiting, growth and developmental delay. Abnormal hair, hepatomegaly, and hepatic fibrosis are unique features of this disorder. Twelve patients with argininosuccinate lyase deficiency were ascertained between 4 and 6 weeks of age by urine amino acid screening. One infant in a previously identified family was diagnosed shortly after birth. Diagnosis was confirmed by enzyme assay in red blood cells and/or skin fibroblasts. At the time of last follow-up, patients had been followed for 13–33 years. All patients were asymptomatic at detection, 7 had slightly increased blood ammonia, and all were initially treated with low-protein diet. Utilization of 14C-citrulline by intact skin fibroblasts measured by 14C incorporation into macromolecules was 74–135% of the control mean for 7 of the 8 patients studied. Nine patients had normal development, 4 had learning disability, 6 had EEG abnormalities, 3 had seizure disorder. None had any episodes of hyperammonemic coma. None had hepatomegaly. Patients detected by screening had higher enzyme activity measured by the 14C-citrulline incorporation assay than comparison groups of patients with neonatal-onset and with late-onset detected by clinical disease. The ability to utilize 14C-citrulline by intact fibroblasts seems to correlate with clinical outcome and may have prognostic value. It is likely that early diagnosis and treatment contributed to the relatively mild clinical course of the study group.

Clinical and molecular genetic analysis for 7 patients from 5 pedigrees with 17a-hydroxylase/17, 20 lyase deficiency

To investigate the clinical and genetic characteristics of 7 patients from 5 families with 17a-hydroxylase/17,20 lyase deficiency (17OHD) and the CYP17A1 mutation in Chinese. Clinical features and laboratory data were collected from 5 families with 17OHD. PCR direct sequencing was performed to screen the mutation of CYP17A1 gene of the patients. Polymerase chain reaction-restriction fragment length polymorphism(PCR-RFLP) and sequencing were performed to screen the mutations of CYP17A1 gene in 288 healthy individuals from Shandong province. Seven patients (5 of them were 46,XX; 2 were 46,XY) had typical clinical presentation of sexual infantilism, hypertension and hypokalemia. Hormone profile indicated decreased plasma cortisol and sex hormones, and elevated blood adrenocorticotrophic hormone (ACTH). TAC329AA and H373L in exon 6 and D487_F489del in exon 8 were identified from the patients. One heterozygote for D487_F489del was identified in 288 healthy controls. The TAC329AA and D487_F489del of the CYP17A1 gene were the most frequent mutations in Chinese with 17OHD.There might be certain frequency of heterozygotes for D487_F489del in Chinese population.

173. Phenotypic Correction of the Hypomorphic Mouse Model of Argininosuccinate Lyase Deficiency Using Small Molecules and Gene Therapy

173. Phenotypic Correction of the Hypomorphic Mouse Model of Argininosuccinate Lyase Deficiency Using Small Molecules and Gene Therapy

Pilot use of the early motor repertoire in infants with inborn errors of metabolism: Outcomes in early and middle childhood

Background Predicting later outcome in neonates presenting with severe inborn errors of metabolism (IEM) is difficult. The assessment of the early motor repertoire is a reliable method of evaluating the integrity of the central nervous system in young infants. This method is based on an age-specific qualitative assessment of general movements (GMs, 0–8 weeks of age), fidgety movements (FMs) and the concurrent motor repertoire (9–20 weeks of age). Aim To determine the quality of the early motor repertoire (at 0–20 weeks post term age) in relation to later neurological outcome in infants with severe IEM. Study design Prospective cohort study. The quality of the motor repertoire was assessed from serial videotape recordings. Subjects Five infants with IEM. Four presented with a severe IEM in the neonatal period: an undefined gluconeogenesis defect, propionic acidemia, arginosuccinate synthetase and arginosuccinate lyase deficiency. One neonate was antenatally diagnosed with arginosuccinate synthetase deficiency. Outcome measures Outcome at the age of at least 18 m was determined by neurological examination and developmental tests. Results All infants initially had abnormal GMs: hypokinesia, followed by GMs of a poor repertoire. The quality of the early motor repertoire normalised in 3 infants, and remained abnormal in 2. The more severe and persistent abnormalities of the motor repertoire were considered with the more abnormal neurological and developmental scores, later on. Conclusions The quality of the early motor repertoire might be related to later neurological outcome in infants with inborn errors of metabolism.

Characterization of genotype ‐ phenotype correlations in Adenylosuccinate Lyase (ADSL) Deficiency

ADSL deficiency is inherited disorder of purine metabolism affecting mainly central nervous system. Three forms differing in severity of symptoms and correlating negatively with ratios of accumulating SAdo/SAICAr in body fluids were established. The mechanisms leading to selective neuronopathy and underlying the clinical and biochemical heterogeneity are unknown.We analysed 22 patients, identified 16 ADSL mutations, expressed and characterized catalytic properties of recombinant wild type and mutant proteins, investigated expression patterns of ADSL in available tissues from 3 patients and correlated these data with patients' clinical and biochemical presentation.We found that phenotype severity corresponds with residual enzyme activity (calculated as a mean of homoallelic activities), but the mutant enzymes displayed proportional decrease in activity to both of its substrates, so no ground for the varied SAdo/SAICAr ratios was found.Western blot and immunohistochemistry analyses showed in patients generally reduced amounts of ADSL in investigated tissues.Our results suggest that selective affection of central nervous system is caused by toxic effects of accumulating SAdo‐SAICAr. Phenotype's heterogeneity may be explained by differential activity of metabolite transport across blood‐brain barrier in individual cases.This work was supported by grants GACR 301070600 and MSM CR 20620806.

Treatment of a Newborn with Urea-Cycle-Disorder and Cerebral Edema with Venovenous Hemodiafiltration and Therapeutic Hypothermia

We report about a term newborn with urea-cycle disorder with severe cerebral edema in which the pharmacological treatment was combined with venovenous hemodiafiltration (VVHDF) and therapeutic hypothermia. A 50h old boy was admitted at a NICU in an external hospital because of convulsions and respiratory failure. Initial metabolic workup showed ammonia 2320µmol/l and the boy was transferred to our hospital. Initial examination showed a ventilated newborn with hepatomegalia and severe hypotension and ammonia concentrations of 2391µmol/l under treatment with Arginin-HCL and Na-Benzoat. Cranial ultrasound (CUS) showed a cerebral edema with systolic peaks and a pulsatility index (PI) of 3.0. After placing of a dual lumen catheter in the right jugularian vein VVHDF was started. In addition neuroprotection was performed by cooling the boy to a rectal temperature of 33°C for the first 24h using CritiCool cooling therapy system. Then the boy was rewarmed stepwise to 36°C over the next 48h. Ammonia concentration was decreased during the first 3h to 830.4µmol/l by VVHDF and CUS showed a significant improvement of the cerebral blood flow. VVHDF was stopped 3h later at ammonia 224.3µmol/l. There was no rebound of hyperammonemia and CUS showed regular findings. The metabolic investigation revealed an Argininosuccinate lyase deficiency. After Extubation at day 10, the boy was discharged at day 38. The 2 months follow up showed an adequate neurological development despite the classic signs of metabolic stroke in MRI. Conclusion: Life-threatening cerebral edema in newborns with inborn urea-cycle defects can be treated effectively by the combination of VVHDF with therapeutic hypothermia.

Striatum is more vulnerable to oxidative damage induced by the metabolites accumulating in 3-hydroxy-3-methylglutaryl-CoA lyase deficiency as compared to liver

The present work investigated the in vitro effects of 3-hydroxy-3-methylglutarate, 3-methylglutarate, 3-methylglutaconate and 3-hydroxyisovalerate, which accumulate in 3-hydroxy-3-methylglutaric aciduria, on important parameters of oxidative stress in striatum and liver of young rats, tissues that are injured in this disorder. Our results show that all metabolites induced lipid peroxidation (thiobarbituric acid-reactive substances increase) and decreased glutathione levels in striatum, whereas 3-hydroxy-3-methylglutarate, besides inducing the strongest effect, also altered thiobarbituric acid-reactive substances and glutathione levels in the liver. Furthermore, 3-hydroxy-3-methylglutarate, 3-methylglutarate and 3-methylglutaconate oxidized sulfhydryl groups in the striatum, but not in the liver. Our data indicate that 3-hydroxy-3-methylglutarate behaves as a stronger pro-oxidant agent compared to the other metabolites accumulating in 3-hydroxy-3-methylglutaric aciduria and that the striatum present higher vulnerability to oxidative damage relatively to the liver.

3‐Hydroxy‐3‐methylglutaryl‐coenzyme A lyase deficiency: Initial presentation in a young adult

3-Hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) lyase deficiency is a rare inborn error affecting leucine catabolism and ketogenesis, usually presenting in the neonatal period. Late forms of the disease have been detected in infancy and childhood, but not in adults. We report a case of HMG-CoA lyase deficiency with initial presentation in a 29-year-old adult with no prior history of the disease, which to our knowledge is the first case described with presentation at this age.

Novel MRI and clinical findings in a boy with adenylosuccinate lyase deficiency

Adenylosuccinate lyase (ADSL-E.C.4.3.2.2.) deficiency is a rare autosomal recessive metabolic disease of purines nucleotide synthesis affecting predominantly the central nervous system. We present a case of a 4.5-year-old boy with ADSL deficiency, developmental delay, hypotonia and epilepsy. In a series of three consecutive magnetic resonance examinations we observed not only reduced myelination and progressive atrophy of the brain that were reported before but also demyelination of previously normal white matter, correlating with clinical deterioration.

Bloodspot acylcarnitine and amino acid analysis in cord blood samples: efficacy and reference data from a large cohort study

In order to test the feasibility of cord blood screening for inherited metabolic disease, a two-year cohort study of births in six obstetric units from five towns in the north of England was undertaken. These towns have a high prevalence of consanguineous marriages, largely among the immigrant Asian community. The purpose of the study was to determine whether early detection of metabolic disease was possible and whether early intervention would improve prognosis. Following parental consent, cord blood samples were collected at birth and analysed for acylcarnitine and amino acid profiles by tandem mass spectrometry in one of two laboratories. One laboratory used butylated derivatives, the other used underivatized samples. The same laboratories performed routine blood spot neonatal screening at 5-7 days of age on these babies. Patients with positive results were investigated and treated by a metabolic paediatrician as soon as possible. 24,983 births were examined. 12,952 samples were analysed as butyl derivatives, 12,031 samples were analysed underivatized. The following disorders were detected: medium-chain acyl-CoA dehydrogenase (MCAD) deficiency (1 case), 3-methylcrotonyl-CoA carboxylase (MCC) deficiency (2 cases), maternal carnitine transporter defect (2 cases), maternal MCC (1 case). The following disorders were diagnosed subsequently but were not detected by the cord blood screening: phenylketonuria (PKU) (1 case), maple syrup urine disease (MSUD) (2 cases), argininosuccinic aciduria (1 case), methylmalonic acidaemia (MMA) (1 case), glutaric aciduria type 2 (1 case), MCAD deficiency (2 cases), 3-hydroxy-3-methylglutaryl-CoA lyase deficiency (1 case). Comprehensive reference data for all analytes by both methods were obtained. Cord blood testing is of limited value in detecting inherited metabolic disease. The metabolites associated with most disorders examined were not elevated in cord blood. Some maternal disorders, carnitine transporter defect and 3-methlycrotonyl-CoA carboxylase deficiency, are detected. These remain of uncertain clinical significance. Comprehensive reference data have been obtained that will facilitate future interpretation of studies in cord blood.

A Case of Dilated Cardiomyopathy Associated with 3-Hydroxy-3-Methylglutaryl-Coenzyme A (HMG CoA) Lyase Deficiency

3-hydroxy-3-methylglutaryl-coenzyme A (HMG CoA) lyase deficiency is an inborn error of metabolism characterized by impairment of ketogenesis and leucine catabolism resulting in an organic acidopathy. In 1994, a case of dilated cardiomyopathy and fatal arrhythmia was reported in a 7-month-old infant. We report a case of dilated cardiomyopathy in association with HMG CoA lyase deficiency in a 23-year-old man with the acute presentation of heart failure. To our knowledge, this is the first case reported in an adult.

Population screening in a Druze community: the challenge and the reward

PurposeThe Druze community is characterized by consanguinity and endogamy, and by reluctance to genetic testing and technological interventions for the prevention of birth defects. Multiple patients with four rare and severe inborn errors of metabolism cerebrotendinous xanthomatosis, prolidase deficiency, argininosuccinate lyase deficiency, and carbamyl phosphate synthetase I deficiency were identified in an isolated Druze village in northern Israel. The aims of this study were to identify couples at risk for four inherited diseases, and to prevent birth defects in a community presenting religious and cultural obstacles to genetic testing. MethodsA genetic screening and counseling program in a high-risk community. ResultsThe 1425 residents who attended group genetic counseling sessions between 2003 and 2007 consented to genetic testing. We identified 217 carriers for either one or two disease causing mutations. High carrier frequencies for cerebrotendinous xanthomatosis, prolidase deficiency, argininosuccinate lyase deficiency, and carbamyl phosphate synthetase I deficiency were identified as 1:11, 1:21, 1:41, and 1:95, respectively. Fifty-eight percent (125) of the carriers' spouses agreed to genetic counseling and testing. Ten couples at risk for affected offspring were identified and offered prenatal genetic counseling and diagnosis. ConclusionsThe genetic screening program, the first of its kind reported in a Druze community, was well received. We expect this program to increase awareness of genetic counseling, to contribute to disease prevention, and to serve as a model for other isolated communities.

Molecular analysis of Taiwanese patients with 3-Hydroxy-3-methylglutaryl CoA lyase deficiency

Background 3-Hydroxy-3-methylglutaryl CoA lyase deficiency (HL deficiency) is a rare autosomal recessive mitochondrial disease characterized by a deficiency in the enzyme 3-Hydroxy-3-methylglutaryl CoA lyase (HMGCL). Here, we report on novel mutations identified in the HMGCL gene in 2 Taiwanese patients with HL deficiency. Methods Analysis of organic acids in urine was performed using gas chromatography-mass spectrometry to confirm HL deficiency in the two subjects. The mutations in their HMGCL genes then were determined by direct sequencing. In addition, the effect of a splice site mutation was determined using reverse transcription-polymerase chain reactions (RT-PCR). Results A total of 3 novel mutations in the HMGCL gene were revealed by molecular analysis: one missense mutation (c.494G > T, p.Arg165Gln) and 2 splice site mutations (IVS3 + 1G > A, IVS6-1G > A). The results of RT-PCR revealed that an IVS3 + 1G > A mutation leads to skipping of exon3. We also calculated that the incidence of HL deficiency in Taiwan is < 1 per 1,000,000 live births. Conclusions The results of this study suggest that unique HMGCL gene mutations exist in Taiwanese HL deficiency patients. Therefore, HMGCL gene profiling may be useful in genetic counseling for families affected by HL deficiency.

Misleading behavioural phenotype with adenylosuccinate lyase deficiency

Adenylosuccinate lyase deficiency is a rare autosomal disorder of de novo purine synthesis, which results in the accumulation of succinylpurines in body fluids. Patients with adenylosuccinate lyase deficiency show a variable combination of mental retardation, epilepsy and autistic features and are usually discovered during screens for unexplained encephalopathy using the Bratton-Marshall assay that reveals the excretion of the succinylaminoimidazolecarboxamide riboside (SAICAr). Here, we report on two sisters aged 11 and 12 years presented with global developmental delay, motor apraxia, severe speech deficits, seizures and behavioural features, which combined excessive laughter, a very happy disposition, hyperactivity, a short attention span, the mouthing of objects, tantrums and stereotyped movements that gave a behavioural profile mimicking Angelman syndrome. Both patients had an increased succinyladenosine/SAICAr ratio of 1.6, and exhibited a novel homozygous missense mutation (c.674T>C; p.Met225Thr) in the exon 6 of the ADSL gene. We suggest that these clinical features might be a new presentation of adenylosuccinate lyase deficiency. On the basis of this observation, although adenylosuccinate lyase deficiency is a rare disorder, this diagnosis should be considered in patients with mental retardation and a behavioural profile suggestive of Angelman syndrome.