[Show abstract][Hide abstract] ABSTRACT: Two sisters were diagnosed in their adulthood with aromatic L-amino acid decarboxylase (AADC) deficiency (OMIM#608643). They experienced early myasthenia-like manifestations, myoclonic jerks, oculogyric crises, tremors, and developmental delay during childhood; clinical stabilization afterwards; and spontaneous improvement during adolescence and young adulthood. Two novel pathogenic mutations on DDC gene [p.Tyr37Thrfs*5 (c.105delC) and p.F237S (c.710 T>C)] were associated with undetectable enzyme activity in plasma and only a mild reduction of biogenic amines in cerebrospinal fluid (CSF). The increase of both 3-O-methyldopa and 5-hydroxytryptophan on CSF was the most relevant biochemical alteration denoting AADC defect in these subjects. Transdermal rotigotine remarkably improved their gross motor functions and the asthenic status they complained. The present cases broaden the phenotypic spectrum of AADC deficiency and suggest that (1) AADC defect is not a progressive neurological disease and behaves rather as a neurodevelopmental disorder that improves during the second decade of life; (2) treatment-naïve adults can still respond well to neurotransmitter therapy; and (3) the possibility of a mild presentation of AADC deficiency should be considered when examining young adults with asthenic and parkinsonian symptoms.
[Show abstract][Hide abstract] ABSTRACT: β-ureidopropionase (βUP) deficiency is an autosomal recessive disease characterized by N-carbamyl-β-amino aciduria. To date, only 16 genetically confirmed patients with βUP deficiency have been reported. Here, we report on the clinical, biochemical and molecular findings of 13 Japanese βUP deficient patients. In this group of patients, three novel missense mutations (p.G31S, p.E271K, and p.I286T) and a recently described mutation (p.R326Q) were identified. The p.R326Q mutation was detected in all 13 patients with eight patients being homozygous for this mutation. Screening for the p.R326Q mutation in 110 Japanese individuals showed an allele frequency of 0.9 %. Transient expression of mutant βUP enzymes in HEK293 cells showed that the p.E271K and p.R326Q mutations cause profound decreases in activity (≤ 1.3 %). Conversely, βUP enzymes containing the p.G31S and p.I286T mutations possess residual activities of 50 and 70 %, respectively, suggesting we cannot exclude the presence of additional mutations in the non-coding region of the UPB1 gene. Analysis of a human βUP homology model revealed that the effects of the mutations (p.G31S, p.E271K, and p.R326Q) on enzyme activity are most likely linked to improper oligomer assembly. Highly variable phenotypes ranging from neurological involvement (including convulsions and autism) to asymptomatic, were observed in diagnosed patients. High prevalence of p.R326Q in the normal Japanese population indicates that βUP deficiency is not as rare as generally considered and screening for βUP deficiency should be included in diagnosis of patients with unexplained neurological abnormalities.
Journal of Inherited Metabolic Disease 02/2014; · 4.07 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: ß-ureidopropionase is the third enzyme of the pyrimidine degradation pathway and catalyzes the conversion of N-carbamyl-ß-alanine and N-carbamyl-ß-aminoisobutyric acid to ß-alanine and ß-aminoisobutyric acid, ammonia and CO(2). To date, only five genetically confirmed patients with a complete ß-ureidopropionase deficiency have been reported. Here, we report on the clinical, biochemical and molecular findings of 11 newly identified ß-ureidopropionase deficient patients as well as the analysis of the mutations in a three-dimensional framework. Patients presented mainly with neurological abnormalities (intellectual disabilities, seizures, abnormal tonus regulation, microcephaly, and malformations on neuro-imaging) and markedly elevated levels of N-carbamyl-ß-alanine and N-carbamyl-ß-aminoisobutyric acid in urine and plasma. Analysis of UPB1, encoding ß-ureidopropionase, showed 6 novel missense mutations and one novel splice-site mutation. Heterologous expression of the 6 mutant enzymes in Escherichia coli showed that all mutations yielded mutant ß-ureidopropionase proteins with significantly decreased activity. Analysis of a homology model of human ß-ureidopropionase generated using the crystal structure of the enzyme from Drosophila melanogaster indicated that the point mutations p.G235R, p.R236W and p.S264R lead to amino acid exchanges in the active site and therefore affect substrate binding and catalysis. The mutations L13S, R326Q and T359M resulted most likely in folding defects and oligomer assembly impairment. Two mutations were identified in several unrelated ß-ureidopropionase patients, indicating that ß-ureidopropionase deficiency may be more common than anticipated.
Biochimica et Biophysica Acta 04/2012; 1822(7):1096-108. · 4.66 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Adenosine deaminase (ADA) deficiency is a rare metabolic disease causing severe combined immunodeficiency (SCID). An assay to determine ADA activity in dried blood spots was developed using reversed-phase HPLC. The assay was linear with reaction times up to at least 4 hours, and protein concentrations up to at least 2.2 mg/ml. The intra-assay CV and the inter-assay CV for the complete assay was 3.5 and 8.4%, respectively. The ADA activity in a control blood spot, stored at 4 degrees C, remained stable for at least one year. Only a slightly decreased ADA activity (35 +/- 13 nmol/mg/h, n = 4) was observed in heterozygotes for a c.704G > A mutation in the ADA gene when compared to that observed in controls (41 +/- 13 nmol/mg/h, n = 108). In addition, increased ADA activity as found in a rare form of congenital anemia can be assessed, as observed in a bloodspot from a patient diagnosed with Diamond Blackfan anemia (ADA activity 150 nmol/mg/h).
[Show abstract][Hide abstract] ABSTRACT: Purine nucleoside phosphorylase (PNP) deficiency results in severe T cell dysfunction and hypouricemia. An assay to measure PNP activity in dried blood spots was developed using reversed-phase HPLC. The assay was linear with reaction times between 5 and 12.5 minutes, and protein concentrations ranging from 0.4 to 1.8 mg/ml. The intra-assay CV and the inter-assay CV for the complete assay was <3.6%. The PNP activity in a control blood spot, stored at 4 degrees C, remained stable for at least one year. In a patient suffering from a PNP deficiency, the residual PNP activity was only 0.3% compared to that observed in controls (1431 +/- 238 nmol/mg/h, n = 114). The PNP activity (483 +/- 35 nmol/mg/h, n = 3) in heterozygotes for the c.614A > C mutation (p.E205A) in the PNP gene was 34% compared to controls. Thus, the analysis of the PNP activity in blood spots can readily detect patients with a PNP deficiency.
[Show abstract][Hide abstract] ABSTRACT: Dihydropyrimidine dehydrogenase (DPD) deficiency is an autosomal recessive disorder of the pyrimidine degradation pathway. In a patient presenting with convulsions, psychomotor retardation and Reye like syndrome, strongly elevated levels of uracil and thymine were detected in urine. No DPD activity could be detected in peripheral blood mononuclear cells. Analysis of the gene encoding DPD (DPYD) showed that the patient was homozygous for a novel c.505_513del (p.169_171del) mutation in exon 6 of DPYD.
[Show abstract][Hide abstract] ABSTRACT: Dihydropyrimidinase (DHP) is the second enzyme of the pyrimidine degradation pathway and catalyses the ring opening of 5,6-dihydrouracil and 5,6-dihydrothymine. To date, only 11 individuals have been reported suffering from a complete DHP deficiency. Here, we report on the clinical, biochemical and molecular findings of 17 newly identified DHP deficient patients as well as the analysis of the mutations in a three-dimensional framework. Patients presented mainly with neurological and gastrointestinal abnormalities and markedly elevated levels of 5,6-dihydrouracil and 5,6-dihydrothymine in plasma, cerebrospinal fluid and urine. Analysis of DPYS, encoding DHP, showed nine missense mutations, two nonsense mutations, two deletions and one splice-site mutation. Seventy-one percent of the mutations were located at exons 5-8, representing 41% of the coding sequence. Heterologous expression of 11 mutant enzymes in Escherichia coli showed that all but two missense mutations yielded mutant DHP proteins without significant activity. Only DHP enzymes containing the mutations p.R302Q and p.T343A possessed a residual activity of 3.9% and 49%, respectively. The crystal structure of human DHP indicated that the point mutations p.R490C, p.R302Q and p.V364M affect the oligomerization of the enzyme. In contrast, p.M70T, p.D81G, p.L337P and p.T343A affect regions near the di-zinc centre and the substrate binding site. The p.S379R and p.L7V mutations were likely to cause structural destabilization and protein misfolding. Four mutations were identified in multiple unrelated DHP patients, indicating that DHP deficiency may be more common than anticipated.
Biochimica et Biophysica Acta 03/2010; 1802(7-8):639-48. · 4.66 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Dihydropyrimidine dehydrogenase (DPD) deficiency is an infrequently described autosomal recessive disorder of the pyrimidine
degradation pathway and can lead to mental and motor retardation and convulsions. DPD deficiency is also known to cause a
potentially lethal toxicity following administration of the antineoplastic agent 5-fluorouracil. In an ongoing study of 72
DPD deficient patients, we analysed the molecular background of 5 patients in more detail in whom initial sequence analysis
did not reveal pathogenic mutations. In three patients, a 13.8kb deletion of exon 12 was found and in one patient a 122kb
deletion of exon 14–16 of DPYD. In the fifth patient, a c.299_302delTCAT mutation in exon 4 was found and also loss of heterozygosity of the entire DPD
gene. Further analysis demonstrated a de novo deletion of approximately 14Mb of chromosome 1p13.3–1p21.3, which includes
DPYD. Haploinsufficiency of NTNG1, LPPR4,
GPSM2, COL11A1 and VAV3 might have contributed to the severe psychomotor retardation and unusual craniofacial features in this patient. Our study
showed for the first time the presence of genomic deletions affecting DPYD in 7% (5/72) of all DPD deficient patients. Therefore, screening of DPD deficient patients for genomic deletions should be
Human Genetics 06/2009; 125(5):581-590. · 4.63 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Dihydropyrimidine dehydrogenase (DPD) deficiency is a rare defect of the first step of the pyrimidine catabolic pathway. Patients with a complete enzyme deficiency may be clinically asymptomatic or suffer from neurological abnormalities of various severity. We report a case of an 8-year-old girl with psychomotor retardation and mild course of the disease. Analysis of urine showed strongly elevated levels of uracil and thymine, and no DPD activity could be detected in peripheral blood mononuclear cells. Sequence analysis of the DPD gene (DPYD) revealed that our patient was homozygous for the common splice-site mutation IVS14+1G > A, which suggest that the carrier status for this mutation may be not rare in the Polish population.
[Show abstract][Hide abstract] ABSTRACT: Dihydropyrimidine dehydrogenase (DPD) plays a pivotal role in the metabolism of 5-fluorouracil (5FU). In patients treated with capecitabine or 5FU combined with other chemotherapeutic drugs, DPD activity in peripheral blood mononuclear cells was increased in patients experiencing grade I/II neutropenia. In contrast, decreased DPD activity proved to be associated with grade I/II dermatological toxicity, including hand-foot syndrome. Thus, patients with a low-normal or high-normal DPD activity proved to be at risk of developing mild toxicity upon treatment with 5FU-based chemotherapy, demonstrating the important role of DPD in the etiology of toxicity associated with 5FU and the catabolites of 5FU.
[Show abstract][Hide abstract] ABSTRACT: There is an increased risk of developing bone marrow depression and infections during azathioprine therapy for inflammatory bowel disease. Patients with low or absent thiopurine S-methyltransferase (TPMT) activity have an increased risk of developing myelotoxicity. We describe a patient who developed pancytopenia combined with cytomegalovirus pneumonia after several years of azathioprine use. The bone marrow depression was probably caused by the viral infection, as all others causative factors were unlikely. Surprisingly, we observed grossly elevated TPMT activity (182 nmol/g/h) during the recovery phase, following the pancytopenic period. After complete recovery of the bone marrow suppression, TPMT activity returned to usual reference activity (43 nmol/g/h). This remarkable change in enzymatic activity of TPMT may be explained by differences in the age of red blood cells, as younger erythrocytes have a higher TPMT activity. Determination of a patient's TPMT status by phenotyping should therefore not be performed just after bone marrow depression or in cases of activated erythropoieses.
Therapeutic Drug Monitoring 06/2008; 30(3):390-3. · 2.23 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Beta-ureidopropionase deficiency (McKusick 606673) is an autosomal recessive condition caused by mutations in the UPB1 gene. To date, five patients have been reported, including one putative case detected through newborn screening. Clinical presentation includes neurological and developmental problems. Here, we report another case of beta-ureidopropionase deficiency who presented with congenital anomalies of the urogenital and colorectal systems and with normal neurodevelopmental milestones. Analysis of a urine sample, because of the suspicion of renal stones on ultrasound, showed strongly elevated levels of the characteristic metabolites, N-carbamyl-beta-amino acids. Subsequent analysis of UPB1 identified a novel mutation 209 G>C (R70P) in exon 2 and a previously reported splice receptor mutation IVS1-2A>G. Expression studies of the R70P mutant enzyme showed that the mutant enzyme did not possess any residual activity. Long-term follow-up is required to determine the clinical significance of the beta-ureidopropionase deficiency in our patient.
Molecular Genetics and Metabolism 03/2008; 93(2):190-4. · 2.83 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Arts syndrome is an X-linked disorder characterized by mental retardation, early-onset hypotonia, ataxia, delayed motor development, hearing impairment, and optic atrophy. Linkage analysis in a Dutch family and an Australian family suggested that the candidate gene maps to Xq22.1-q24. Oligonucleotide microarray expression profiling of fibroblasts from two probands of the Dutch family revealed reduced expression levels of the phosphoribosyl pyrophosphate synthetase 1 gene (PRPS1). Subsequent sequencing of PRPS1 led to the identification of two different missense mutations, c.455T-->C (p.L152P) in the Dutch family and c.398A-->C (p.Q133P) in the Australian family. Both mutations result in a loss of phosphoribosyl pyrophosphate synthetase 1 activity, as was shown in silico by molecular modeling and was shown in vitro by phosphoribosyl pyrophosphate synthetase activity assays in erythrocytes and fibroblasts from patients. This is in contrast to the gain-of-function mutations in PRPS1 that were identified previously in PRPS-related gout. The loss-of-function mutations of PRPS1 likely result in impaired purine biosynthesis, which is supported by the undetectable hypoxanthine in urine and the reduced uric acid levels in serum from patients. To replenish low levels of purines, treatment with S-adenosylmethionine theoretically could have therapeutic efficacy, and a clinical trial involving the two affected Australian brothers is currently underway.
The American Journal of Human Genetics 09/2007; 81(3):507-18. · 11.20 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Dihydropyrimidinase (DHP) is the second enzyme of the pyrimidine degradation pathway and it catalyses the ring opening of 5,6-dihydrouracil and 5,6-dihydrothymine to N-carbamyl-beta-alanine and N-carbamyl-beta-aminoisobutyric acid, respectively. To date, only nine individuals have been reported suffering from a complete DHP deficiency. We report two siblings presenting with strongly elevated levels of 5,6-dihydrouracil and 5,6-dihydrothymine in plasma, cerebrospinal fluid and urine. One of the siblings had a severe delay in speech development and white matter abnormalities, whereas the other one was free of symptoms. Analysis of the DHP gene (DPYS) showed that both patients were compound heterozygous for the missense mutation 1078T>C (W360R) in exon 6 and a novel missense mutation 1235G>T (R412M) in exon 7. Heterologous expression of the mutant enzymes in Escherichia coli showed that both missense mutations resulted in a mutant DHP enzyme without residual activity. Analysis of the crystal structure of eukaryotic DHP from the yeast Saccharomyces kluyveri and the slime mold Dictyostelium discoideum suggests that the W360R and R412M mutations lead to structural instability of the enzyme which could potentially impair the assembly of the tetramer.
Molecular Genetics and Metabolism 07/2007; 91(2):157-64. · 2.83 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Patients with a partial dihydropyrimidine dehydrogenase (DPD) deficiency have an increased risk of developing severe 5-fluorouracil-associated toxicity. We developed a rapid and specific method to measure the DPD activity in peripheral blood mononuclear cells using HPLC tandem-mass spectrometry (HPLC-MS/MS).
The activity of DPD was measured with thymine as the substrate, followed by reversed-phase HPLC combined with electrospray ionization MS/MS and detection of the product dihydrothymine with multiple-reaction monitoring. Stable-isotope labeled dihydrothymine was used as the internal standard.
Dihydrothymine was measured within an analytical run of 10 min, with a lower limit of quantification of 54 microg/L (0.4 micromol/L). The intraassay and interassay variations of the DPD activity assay were both <7%. A linear correlation (R(2) = 0.980; P <0.001) was observed between the HPLC-MS/MS data and those obtained with a reference method using radiolabeled thymine. There were no systematic differences between the 2 methods, and both methods yielded similar results.
The analysis of the DPD activity with HPLC-MS/MS is rapid, accurate, and sufficiently sensitive to be used as a screening method for patients with a DPD deficiency.
[Show abstract][Hide abstract] ABSTRACT: Dihydropyrimidine dehydrogenase (DPD) plays a pivotal role in the metabolism of 5FU. The prognostic significance of DPD activity in peripheral blood mononuclear (PBM) cells and buccal mucosa cells with respect to toxicity was investigated in 44 patients treated with 5FU-leucovorin. Grade III/IV haematological and grade III/IV gastrointestinal toxicity were observed in 25% and 21% of the patients, respectively. No association was observed between the DPD activity in buccal mucosa cells and toxicity. In contrast, the mean DPD activity in PBM cells proved to be increased in patients experiencing grade I/II neutropenia when compared to patients without neutropenia and those suffering from grade III/IV neutropenia (P=0.002). Patients with a high-normal DPD activity proved to be at risk of developing mild toxicity upon treatment with 5FU-leucovorin, suggesting an important role of DPD in the aetiology of toxicity associated with catabolites of 5FU.
European Journal of Cancer 02/2007; 43(2):459-65. · 5.06 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: In this study, we demonstrated that the highest activity of thymidine phosphorylase (TP) was found in peripheral blood mononuclear (PBM) cells followed by that of thrombocytes and granulocytes whereas no activity of TP could be detected in erythrocytes. The activity of TP in leukocytes proved to be intermediate compared to the TP activity observed in PBM cells and granulocytes. The activity of TP also was readily detectable in human fibroblasts.
[Show abstract][Hide abstract] ABSTRACT: Thymidine phosphorylase (TP) catalyses the conversion of thymidine into thymine. A non-radiochemical assay procedure for TP was developed in which thymine was detected at 265 nm after separation with reversed-phase HPLC. A complete separation of thymidine and thymine was achieved in 6 min and the minimum amount of thymine that could be detected was 0.8 pmol. The assay was linear with reaction times, up to at least 4 h, and protein concentrations up to at least 65 μg/ml. Population analysis showed no differences in TP activity between man and women or with increasing age.
Journal of Chromatography B 07/2005; · 2.49 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: beta-Ureidopropionase deficiency is an inborn error of the pyrimidine degradation pathway, affecting the cleavage of N-carbamyl-beta-alanine and N-carbamyl-beta-aminoisobutyric acid. In this study, we report the elucidation of the genetic basis underlying a beta-ureidopropionase deficiency in four patients presenting with neurological abnormalities and strongly elevated levels of N-carbamyl-beta-alanine and N-carbamyl-beta-aminoisobutyric acid in plasma, cerebrospinal fluid and urine. No beta-ureidopropionase activity could be detected in a liver biopsy obtained from one of the patients, which reflected the complete absence of the beta-ureidopropionase protein. Analysis of the beta-ureidopropionase gene (UPB1) of these patients revealed the presence of two splice-site mutations (IVS1-2A>G and IVS8-1G>A) and one missense mutation (A85E). Heterologous expression of the mutant enzyme in Escherichia coli showed that the A85E mutation resulted in a mutant beta-ureidopropionase enzyme without residual activity. Our results demonstrate that the N-carbamyl-beta-amino aciduria in these patients is due to a deficiency of beta-ureidopropionase, which is caused by mutations in the UPB1 gene. Furthermore, an altered homeostasis of beta-aminoisobutyric acid and/or increased oxidative stress might contribute to some of the clinical abnormalities encountered in patients with a beta-ureidopropionase deficiency. An analysis of the presence of the two splice site mutations and the missense mutation in 95 controls identified one individual who proved to be heterozygous for the IVS8-1G>A mutation. Thus, a beta-ureidopropionase deficiency might not be as rare as is generally considered.
Human Molecular Genetics 12/2004; 13(22):2793-801. · 7.69 Impact Factor