Adenine Mutation Research Articles

FAMILIAL NEUROHYPOPHYSEAL DIABETES INSIPIDUS (NHDI) DUE TO A MUTATION IN THE VASOPRESSIN-NEUROPHYSINE II (VP-NPH II) GENE

Autosomal dominant NHDI is a familial form of antidiuretic hormone deficiency, usually expressed in early childhood with polyuria, polydipsia, and an antidiuretic response to exogenous vasopressin or its analog. We report a family with evidence of NHDI in four generations. Diagnosis was confirmed with plasma and urine osmolarity under water restriction, and a good response to DDAVP (VP analog) in the patients receiving treatment. The family, of Russian-German ancestry, lives in the southwest of Buenos Aires province, Argentina. Most affected members did not seek medical attention, as they viewed the symptoms as a natural occurrence in their family, in spite of diuresis over 12 liters a day, and single voiding volumes over 1.5 liters. Phenotypic expression was variable. Molecular studies were performed trying to characterize a mutation of the AVP-NP II gene, encoding AVP, its carrier protein NP II, and a glycoprotein of unknown function. A Guanine to Adenine mutation was detected in the nucleotide 1859, that encodes a change from Glycine to Serine at Aminoacid 57 of NP II. Five different mutations have been reported up to this time. The mutation in this family has also been described in a Japanese kindred.

Diagnosis of acute intermittent porphyria in northern Sweden: an evaluation of mutation analysis and biochemical methods.

To validate the use of a recently observed guanine to adenine mutation in exon 10 in the porphobilinogen deaminase (PBGD) gene as a diagnostic marker of acute intermittent porphyria (AIP). To evaluate the efficiency of the traditional biochemical diagnostic methods. Matched and blinded case-control study (1:4). A primary health care centre in Arjeplog, the National Porphyria Research Unit and a department of clinical genetics in Stockholm. A total of 48/49 (98%) patients over the age of 15 years living in Arjeplog with AIP, diagnosed according to standard clinical and biochemical criteria. For each AIP patient, four controls were matched for age, sex and geographical area and 164/196 (86%) participated. In the validity study, 35 patients were selected as indisputable AIP gene carriers, according to strict biochemical criteria, and 92 matched controls were selected with strict exclusion criteria. Validity, specificity and sensitivity of DNA diagnosis for this AIP mutation. Specificity and sensitivity of traditional biochemical methods. Validity study: the mutation was found in all 35 individuals classified as carriers of AIP. None of the 92 controls had the mutation. Evaluation study: all 48 AIP gene carriers, diagnosed by traditional methods, had the mutation, as had one of the control persons. In an inconclusive group of five persons with heredity for AIP, two had a positive DNA test. The PBGD mutation analysis was found to have full specificity and sensitivity and can be used as the sole diagnostic method in the family complex studied, representing the major AIP mutation in Sweden. The traditional diagnostic methods, used in optimal combinations, work in most cases, but they do not show high precision. However, they must be used when the specific mutation in the PBGD gene is not known.

Molecular basis of genetic variation in debrisoquin hydroxylation in Chinese subjects: polymorphism in RFLP and DNA sequence of CYP2D6.

Debrisoquin hydroxylation phenotype was determined in 124 Chinese persons living in Taiwan, and two poor metabolizers were identified with a urinary metabolic ratio (MR) greater than 12.6. The other subjects, extensive metabolizers, showed a normal frequency distribution of log(MR). Most subjects (50%) showed a 44/29 kb pattern in restriction fragment length polymorphism (RFLP) analysis with use of Xba I, and 30% and 15% of the subjects exhibited a homozygous 29/29 kb and 44/44 kb pattern, respectively. Among extensive metabolizers, subjects with the 44/44 kb pattern had a significant higher log(MR) than those with the 44/29 pattern, and the log(MR) of the subjects with the 44/29 kb pattern was significantly higher than that of the subjects with 29/29 kb pattern. All nine exons and intron 3 of C gamma P2D6 were amplified with polymerase chain reaction (PCR) and sequenced for four extensive metabolizers. Two major polymorphisms were found: one at position 188 of exon 1 and the other at position 4268 in exon 9. With PCR and endonuclease digestion, polymorphisms at exon 1, intron 3, and exon 9 were investigated. Only two of 254 alleles showed a heterozygous guanine at 1934 base pairs (G1934) to adenine (A) mutation, commonly found in white poor metabolizers. Approximately 70% of alleles showed thymine at 188 base pairs (T188), and 76% showed cytosine at 4268 base pairs (C4268) instead of C188 and G4268, as is found in most white subjects. Subjects with T188 or C4268 showed a significant higher log(MR) than subjects with homozygous C188 and G4268. The C/T188, G/A1934, G/C4268, and RFLP polymorphisms may explain the interracial variations between Chinese and white subjects, as well as the genetic variations among Chinese subjects.

Characterization of point mutations in the same arginine codon in three unrelated patients with ornithine transcarbamylase deficiency.

Point mutations in the X-linked ornithine transcarbamylase (OTC) gene have been detected at the same Taq I restriction site in 3 of 24 unrelated probands with OTC deficiency. A de novo mutation could be traced in all three families to an individual in a prior generation, confirming independent recurrence. The DNA sequence in the region of the altered Taq I site was determined in the three probands. In two unrelated male probands with neonatal onset of severe OTC deficiency, a guanine (G) to adenine (A) mutation on the sense strand (antisense cytosine [C] to thymine [T]) was found, resulting in glutamine for arginine at amino acid 109 of the mature polypeptide. In the third case, where the proband was a symptomatic female, C to T (sense strand) transition converted residue 109 to a premature stop. These results support the observation that Taq I restriction sites, which contain an internal CG, are particularly susceptible to C to T transition mutation due to deamination of a methylated C in either the sense or antisense strand. The OTC gene seems especially sensitive to C to T transition mutation at arginine codon 109 because either a nonsense mutation or an extremely deleterious missense mutation will result.

Suppressor system in Bacillus subtilis 168.

Multiple auxotrophic strains of Bacillus subtilis 168 were tested for joint one-step reversion of two or more auxotrophic markers to the wild-type phenotype. Mu8u5u5, a strain requiring leucine, methionine, and threonine, yielded revertants that grew without added methionine or threonine and proved to have a suppressor gene. When transferred by transformation with deoxyribonucleic acid, this suppressor gene also suppressed the adenine mutation in another strain, Mu8u5u6. The one-step double revertants fell into two distinct classes: strains of class su(+) (I) grow well in broth; strains of class su(+) (II) grow poorly. Strains su(+) (II) tend to revert frequently to the su(+) (I) or su(-) state. Conditional lethal mutants of phage phie were isolated which can grow on the su(+) and not on the su(-) strains.

The induction of replicating instabilities by mutagens in Schizosaccharomytes pombe

A replicating instability is defined as an unstable condition in a particular locus or narrow chromosomal region which fulfils two conditions; it continues to give rise to mutational events and it replicates as such, so that an unstable locus in one generation may give rise to several similarly unstable loci in the next. Various chemical treatments are known to produce replicating instabilities in Drosophila; in the present experiments a number of mutagens were tested for their ability to produce replicating instabilities in the fission yeast, Schizosaccharomyces pombe. A purple-adenine strain was used for treatment and mutation were scored at any one of 5 loci in the adenine pathway which, since they occur prior to the block caused by the purple adenine mutation, are recognised by a change in colony colour from red into white. A replicating instability was presumed to have occurred when a red white mosaic colony on replating yielded not only stable red and white progeny but also ywo or more red white mosaics, the mutation to white having occurred at the same locus in parent and offspring mosaics. Three the of mutagens tested—ethylmethane sulphonate, nitrosomethylguanidine and ultraviolet light—proved very effective in producing replicating instabilities. Hydroxylamine and nitrous acid were, at best, weakly effective. Spurious mosaicism due to clamping was excluded by various tests. Mutations in unstable lines usually were from red to white (forward mutations); a few were from white to red (reverse mutations). In some cases the same mosaic seemed to give rise to both kinds of mutation, but this observation needs retesting.

Regulation and Coordination of Purine and Pyrimidine Biosyntheses in Yeast: I. Regulation of Purine Biosynthesis and Its Relation to Transient Changes in Intracellular Nucleotide Levels

The control of purine biosynthesis in a yeast mutant deficient for uracil, adenine, and histidine has been studied in vivo. The adenine mutation causes accumulation of aminoimidazole ribotide in the cells. The control curve relating steady-state purine nucleotide level in the cell to rate of synthesis in the de novo purine synthetic pathway has been determined. Control in the cell depends on a feedback mechanism involving end-product inhibition. The transient responses of the purine nucleotide pool to changes in adenine input have been studied. Under certain conditions the pool overshoots when shifting from one steady-state to another. Transient changes in nucleotide levels are followed by inverse changes in the rate of attempted de novo purine synthesis. A study of the transient responses of specific intracellular nucleotides suggests that inosinic acid controls the rate of attempted purine synthesis. The transient response of nucleic acid synthesis rate to changes in nucleotide levels was studied and the implications for regulation of nucleic acid synthesis discussed.