Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.4.2.8 (hypoxanthine-guanine phosphoribosyltransferase)
 2,527 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A nonsense mutation at the CpG-site in the codon for Arg(169) in the gene for hypoxanthine phosphoribosyltransferase (hprt) was identified by genomic polymerase chain reaction (PCR) and DNA sequencing in cultured fibroblasts from two brothers with Lesch Nyhan's syndrome. The recurrence of mutation at this CpG-site in several unrelated Lesch-Nyhan families suggests that deamination of 5-methylcytosine is a possible mechanism for mutagenesis. The level of hprt-mRNA in the fibroblasts of the patients was similar to that in healthy controls, whereas hprt-enzyme activity was not detectable. The mutation in this family was also identified in five female relatives and prenatally in a male fetus. Unexpectedly, results from hair follicle analyses and fibroblast selection studies in 8-azaguanine and 6-thioguanine medium showed a non-carrier phenotype in three of the female heterozygotes, whereas X-inactivation mosaicism was demonstrated in one heterozygote. A possible explanation for the apparent non-random X-inactivation in this family is the co-existence of the hprt mutation with an undefined X-linked lethal mutation. This observation is of practical relevance for carrier detection in other Lesch-Nyhan families.
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PMID:Mutation analysis and prenatal diagnosis in a Lesch-Nyhan family showing non-random X-inactivation interfering with carrier detection tests. 161 89

We have determined the genetic stability of three independent intragenic human HPRT gene duplications and the structure of each duplication at the nucleotide sequence level. Two of the duplications were isolated as spontaneous mutations from the HL60 human myeloid leukemia cell line, while the third was originally identified in a Lesch-Nyhan patient. All three duplications are genetically unstable and have a reversion rate approximately 100-fold higher than the rate of duplication formation. The molecular structures of these duplications are similar, with direct duplication of HPRT exons 2 and 3 and of 6.8 kb (HL60 duplications) or 13.7 kb (Lesch-Nyhan duplication) of surrounding HPRT sequence. Nucleotide sequence analyses of duplication junctions revealed that the HL60-derived duplications were generated by unequal homologous recombination between clusters of Alu repeats contained in HPRT introns 1 and 3, while the Lesch-Nyhan duplication was generated by the nonhomologous insertion of duplicated HPRT DNA into HPRT intron 1. These results suggest that duplication substrates of different lengths can be generated from the human HPRT exon 2-3 region and can undergo either homologous or nonhomologous recombination with the HPRT locus to form gene duplications.
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PMID:Molecular structure and genetic stability of human hypoxanthine phosphoribosyltransferase (HPRT) gene duplications. 163 5

In humans, congenital deficiency of the enzyme hypoxanthine-guanine phosphoribosyltransferase (HPRT) results in a disorder known as the Lesch-Nyhan syndrome. Patients with this disorder exhibit a prominent neurobehavioral phenotype that results in part from dysfunction of catecholaminergic systems in the striatum. HPRT-deficient mice produced as animal models for this syndrome curiously exhibit no spontaneous neurobehavioral abnormalities. However, the present study demonstrates that HPRT-deficient mice are more sensitive than their HPRT-normal littermates to the ability of amphetamine to stimulate locomotor or stereotypic behaviors. This behavioral supersensitivity to amphetamine indicates the existence of an underlying subclinical abnormality of catecholaminergic systems in the brains of HPRT-deficient mice, analogous to findings in human Lesch-Nyhan patients.
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PMID:Amphetamine-induced behavioral phenotype in a hypoxanthine-guanine phosphoribosyltransferase-deficient mouse model of Lesch-Nyhan syndrome. 177

A complete deficiency of the purine salvage enzyme, hypoxanthine phosphoribosyltransferase (HPRT; EC 2.4.2.8), in man results in the Lesch-Nyhan (LN) syndrome. Two unrelated patients with the full LN syndrome showed no evidence of a major alteration to the gene encoding HPRT (HPRT) by restriction endonuclease analysis, but exhibited negligible levels of HPRT mRNA on Northern blots. DNA from these patients was characterised further. Amplification, by the polymerase chain reaction (PCR), of individual HPRT-exon fragments from genomic DNA followed by nucleotide (nt) sequence analysis using automated technology, revealed single-base mutations in each patient. One patient has an insertion of a T within exon-2, which places a stop codon in frame, presumably resulting in premature termination of translation of the HPRT mRNA. The other patient has a G----A base substitution at the 5' end of intron-6, at the junction of exon-6 and intron-6. Although dot blot analysis indicated negligible HPRT mRNA in lymphoblast cells from both patients, we were successful in amplifying HPRT cDNA using PCR. Direct nt sequence analysis of the amplified cDNA confirmed the insertion of a T in exon-2 in the one patient and revealed a complete deletion of exon-6 in the other patient, the latter event presumably arising due to aberrant splicing of primary message. Both mutations were also confirmed by hybridisation of amplified genomic DNA with allele-specific oligodeoxyribonucleotide probes. This study illustrates two approaches for analysing DNA mutations at the molecular level and demonstrates the power of PCR technology in the study of genetic diseases.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:The molecular characterisation of HPRT CHERMSIDE and HPRT COORPAROO: two Lesch-Nyhan patients with reduced amounts of mRNA. 184 May 49

The Lesch-Nyhan syndrome is a severe X chromosome-linked human disease caused by a virtual absence of hypoxanthine-guanine phosphoribosyltransferase (HPRT) activity. A partial deficiency in the activity of this enzyme can result in gouty arthritis. To determine the genetic basis for reduction or loss of enzyme activity, we have amplified and sequenced the coding region of HPRT cDNA from four patients: one with Lesch-Nyhan syndrome (HPRTPerth) and three with partial deficiencies of HPRT activity, which have been designated HPRTUrangan, HPRTSwan and HPRTToowong. In all four patients, the only mutation identified was a single base substitution in exons 2 or 3 of the coding region, which in each case predicts a single amino acid substitution in the translated protein. Each base change was confirmed by allele-specific amplification of the patient's genomic DNA. It is interesting to note that the mutation found for HPRTPerth is identical to that reported for HPRTFlint. It appears that the two mutations are de novo events.
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PMID:Hypoxanthine-guanine phosphoribosyltransferase deficiency: analysis of HPRT mutations by direct sequencing and allele-specific amplification. 193 71

Complete hypoxanthine-guanine phosphoribosyltransferase (HPRT) deficiency causes the Lesch-Nyhan syndrome, an X-linked, purine metabolism disorder manifested by hyperuricemia, hyperuricaciduria, and neurologic dysfunction. Partial HPRT deficiency causes hyperuricemia and gout. One requirement for understanding the molecular basis of HPRT deficiency is the determination of which amino acids in this salvage enzyme are necessary for structural or catalytic competence. In this study we have used the PCR coupled with direct sequencing to determine the nucleotide and subsequent amino acid changes in 22 subjects representing 17 unrelated kindreds from the United Kingdom. These mutations were confirmed by using either RNase mapping or Southern analyses. In addition, experiments were done to determine enzyme activity and electrophoretic mobility, and predictive paradigms were used to study the impact of these amino acid substitutions on secondary structure.
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PMID:Identification of 17 independent mutations responsible for human hypoxanthine-guanine phosphoribosyltransferase (HPRT) deficiency. 201 42

Hypoxanthine--guanine phosphoribosyltransferase (HPRT) is a purine salvage enzyme that catalyzes the conversion of hypoxanthine to inosine monophosphate and guanine to guanosine monophosphate. Previous studies of mutant HPRT proteins analyzed at the molecular level have shown a significant heterogeneity. This investigation further verifies this heterogeneity and identifies insertions, deletions, and point mutations. The direct sequencing of the polymerase chain reaction-amplified product of reverse-transcribed HPRT mRNA enabled the rapid identification of the mutations found in 17 previously uncharacterized cell lines derived from patients with the Lesch-Nyhan syndrome.
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PMID:Determination of the mutations responsible for the Lesch-Nyhan syndrome in 17 subjects. 207 Nov 57

Extreme degrees of hypoxanthine phosphoribosyltransferase (HPRT) deficiency in man are associated with gross sex-linked neurological dysfunction, gout and urinary stones (the Lesch-Nyhan or 'complete HPRT-deficiency' syndrome). The less severe degrees of enzyme deficiency (sex-linked recessive gout and/or urolithiasis or the 'partial HPRT-deficiency' syndrome) may be associated with minor neurological manifestations. Whole body purine synthesis de novo is accelerated in both these groups of patients. A strain of mice with an experimentally produced mutation at the HPRT locus showed some residual 'apparent HPRT activity' in brain, liver, testicular, splenic, kidney and ovarian tissues but not in erythrocyte haemolysates. The mutation removes exons 1 and 2 of the coding region of the gene together with the promotor and about 10 kb of upstream sequence from the gene. It is therefore possible that the observed 'apparent HPRT activity' in these mice is due to the operation of an alternative metabolic pathway. Purine synthesis de novo was markedly accelerated in their brain, testicular, splenic and kidney tissues. It was not accelerated in the liver tissue of male mice hemizygous for the mutation and the degree of acceleration in the female homozygotes only just reached statistical significance at the p = 0.02 level. This observation casts doubt on the importance of modulations in the rate of hepatic purine synthesis de novo as a mechanism for maintaining a steady supply of purines for translocation to other organs.
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PMID:Purine synthesis de novo and salvage in hypoxanthine phosphoribosyltransferase-deficient mice. 209 36

1. The synthesis of nicotinamide-adenine dinucleotide from nicotinamide and nicotinic acid was compared over different time scales at both physiological (0.7 mumol/l) and high (0.2-3 mmol/l) substrate concentrations in erythrocytes from three patients with hypoxanthine-guanine phosphoribosyltransferase (hypoxanthine phosphoribosyltransferase, EC 2.4.2.8) deficiency (including one Lesch-Nyhan patient) and from one patient with phosphoribosylpyrophosphate synthetase superactivity. The above disorders are associated with grossly altered erythrocyte nicotinamide-adenine dinucleotide levels. 2. At the physiological substrate concentration and incubation times up to 2 h, nicotinamide proved the most efficient nicotinamide-adenine dinucleotide precursor for erythrocytes from both patients and control subjects. The conversion of nicotinamide to its mononucleotide, but not further metabolism, was impaired in phosphoribosylpyrophosphate synthetase-mutant cells. The Lesch-Nyhan and phosphoribosylpyrophosphate synthetase-mutant cells were unusual in that both showed no further stimulation of nucleotide synthesis at 18 mmol/l Pi compared with 1 mmol/l. 3. At the high substrate concentrations, using 18 mmol/l Pi, nicotinamide was a poor precursor in all instances. Using nicotinic acid, nucleotide formation was 30-fold that from nicotinamide, reaching its maximum at 0.2 mmol/l. Conversion of nicotinic acid to nicotinamide-adenine dinucleotide in the phosphoribosylpyrophosphate synthetase-mutant cells was again grossly impaired. 4. There was no evidence for increased nicotinamide-adenine dinucleotide breakdown in the phosphoribosylpyrophosphate synthetase-mutant cells under any of the above conditions.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Regulation of nicotinamide-adenine dinucleotide synthesis in erythrocytes of patients with hypoxanthine-guanine phosphoribosyltransferase deficiency and a patient with phosphoribosylpyrophosphate synthetase superactivity. 215 55

In humans, deficiency of the enzyme hypoxanthine-guanine phosphoribosyltransferase (HPRT) is associated with a disorder known as Lesch-Nyhan syndrome which includes severe neurobehavioral abnormalities. Several animal models which have been developed to examine the neurobiologic substrates of this disorder have suggested a role for abnormal function in purine/dopamine neurotransmission, but the relationship between HPRT-deficiency and these abnormalities remains unknown. Recently, HPRT-deficient mice have been produced which appear to have similar, though more subtle changes in brain dopamine function. These mice will be useful in elucidating the relationship between HPRT-deficiency and the neurological deficits observed in patients with this disorder.
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PMID:Animal models of Lesch-Nyhan syndrome. 229 45


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