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PubMed1992

A new mutant transthyretin (Arg 10) associated with familial amyloid polyneuropathy.

We report a new kindred with systemic amyloidosis presenting as peripheral neuropathy in the sixth and seventh decades of life. Polymorphism in exon 2 of the transthyretin (TTR) gene was suggested by single strand conformation polymorphism analysis and determined by direct DNA sequencing. We also developed restriction fragment length polymorphism analysis by polymerase chain reaction using a primer with an induced mutation. The point mutation (cytosine for thymine at position 1038 of the TTR gene) is responsible for substitution of arginine for cysteine at position 10 of the TTR molecule. It is hypothesised that the TTR molecules which have no cysteine have a unique structure in heterozygous TTR polymers and are responsible for amyloid fibril formation.

Aged↗
PubMed1993

Ultraviolet-specific mutations in p53 gene in skin tumors in xeroderma pigmentosum patients.

Mutations in the p53 gene were identified in five of eight non-melanoma skin tumors in the sun-exposed areas of xeroderma pigmentosum patients by the polymerase chain reaction and single strand conformation polymorphism analysis followed by sequencing of the DNA. All mutations occurred at the dipyrimidine sites, indicating that they were caused by UV irradiation. Two tumors had multiple mutations, and four tumors had nonsense mutations. Since xeroderma pigmentosum patients are extremely sensitive to UV, the solar UV should have caused the mutations in the p53 gene and the mutations must have played a significant role in UV tumorigenesis.

Adolescent↗
PubMed1989

DNA duplex with the potential to change handedness after every half a turn.

Polymorphic forms of the DNA duplex with long stretches of structural monotony are known. Several alternating purine-pyrimidine sequences have been shown to adopt left-handed Z-conformation. We report a DNA sequence d(CGCGCGATCGAT)n exhibiting alternating right-handed B and left-handed Z helical conformation after every half a turn. Further, this unusual conformation with change in handedness after every six base pairs was induced at physiological superhelical density.

Base Sequence↗
PubMed1992

Detection of a Ha-ras point mutation by polymerase chain reaction-single strand conformation polymorphism analysis in 2-amino-3,4-dimethylimidazo[4,5-f]quinoline-induced mouse forestomach tumors.

Ha-ras activation in forestomach squamous cell carcinomas of CDF1 mice induced by 2-amino-3,4-dimethylimidazo[4,5-f]quinoline (MeIQ), one of the heterocyclic amines isolated from broiled sardine was analyzed. Mutations were detected in two of three primary original carcinomas and two of four cell lines derived from other independent carcinomas by the polymerase chain reaction followed by analysis of single strand conformation polymorphism and direct sequencing. All the mutations detected were G----T transversions at the second letter of codon 13 resulting in an amino acid change from Gly to Val. This finding together with the previous reports on squamous cell carcinomas of the rat Zymbal gland suggest that MeIQ induces a specific type of mutation at a specific site of the Ha-ras gene during squamous cell carcinogenesis, in a species-independent manner.

Animals↗
PubMed1994

Polymerase chain reaction-single strand conformation polymorphism analysis of the p53 gene in paraffin-embedded surgical material from human renal cell carcinomas.

p53 tumour suppressor gene mutations were studied in 118 renal cell carcinomas using paraffin-embedded surgical material. Optimal results were obtained with analysis of exon lengths between 150 and 200 base pairs for polymerase chain reaction. Single strand conformation polymorphism and sequencing analysis revealed only two point mutations (2/118, 2%): one involving codon 135; TGC-->TTC (cysteine-->phenylalanine) and the other codon 175; CGC-->CAC (arginine-->histidine). Both of these cases were classified as granular cell subtype on microscopic observation. The data suggest that the p53 tumour suppressor gene is not related to tumour initiation, promotion, or progression of renal cell carcinomas. However, there is the possibility that granular cell type carcinomas may have a different genetic background from clear cell type renal neoplasms.

Base Sequence↗
PubMed1994

Molecular genetic analysis of the von Recklinghausen neurofibromatosis (NF1) gene using polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP) method.

Von Recklinghausen neurofibromatosis (NF1) is a common autosomal dominant disorder characterized by abnormalities in multiple tissues derived from the embryonic neural crest. The NF1 gene has been mapped to the pericentromeric region of the long arm of chromosome 17. Chromosome walking and sequencing of the NF1 gene have extended it's open reading frame; to date 49 exons have been identified. To investigate the mutation of the NF1 gene, the polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP) method was applied to 4 exons of NF1 genes. We examined the DNAs from 49 samples, including those of 23 Japanese patients with NF1 (4 of these patients developed malignant schwannoma), a patient with segmental neurofibromatosis, and 14 clinically normal controls. A mutational band was detected in an exon of a tumor DNA extracted from a malignant schwannoma of a female NF1 patient. However, the mutation was not found in the germ line DNA of this patient. No mutations were detected in the other samples.

Adolescent↗
PubMed1992

Lack of allelic preference in amplification and loss of the c-myc oncogene in methylcholanthrene-induced mouse sarcomas.

Sarcomas were induced in F1 mice between C57BL/6N and C3H/He strains by subcutaneous injection of methylcholanthrene. The c-myc oncogene was found to be amplified in 16 cases among 43 sarcomas of C57BL/6N x C3H/He mice and 1 case among 5 sarcomas of the reciprocal cross. The origin of the amplified allele was determined by the polymerase chain reaction single strand conformation polymorphism analysis. Among the 17 sarcomas, only one had both of the alleles amplified. The rest of the tumors carried the amplified c-myc allele coming either from C57BL/6N (9 cases) or from C3H/He (8 cases). These results indicate that the c-myc allele is amplified randomly in methylcholanthrene-induced mouse sarcomas irrespective of its origin, such as paternal or maternal allele and C57BL/6N or C3H/He allele. In addition to these changes, the unamplified c-myc oncogene was found to be lost in 12 cases out of the 17 sarcomas with the amplification.

Alleles↗
PubMed1990

Mercury-induced DNA polymorphism: probing the conformation of Hg(II)-DNA via staphylococcal nuclease digestion and circular dichroism measurements.

Exposing native calf thymus DNA to increasing concentrations of Hg(ClO4)2 not only produces dramatic changes in its circular dichroism (CD) but results also in the decrease, and ultimate cessation, of endonucleolytic DNA cleavage by staphylococcal nuclease. Let r = [moles of added Hg(II)]/[mole of DNA base]: the conservative CD spectrum of the DNA B-form becomes nonconservative in appearance at 0.01 less than r less than 0.12 (resembling DNA in C-form geometry) and assumes the spectral characteristics of a left-handed DNA double helix at 0.12 less than r less than or equal to 1.0. DNA cleavage proceeds at or near the rates exhibited by untreated DNA at 0 less than r less than 0.08. At Hg(II) levels of 0.08 less than r less than 0.5, the rate of DNA hydrolysis decreases monotonically with increasing Hg(II) concentrations, and at r greater than 0.4, DNA cleavage ceases. Both the CD changes and the changes in the rate of DNA digestion are totally reversible upon the removal of Hg(II), at least up to r = 1.0, demonstrating that Hg(II) keeps all base pairs in register. For comparison purposes, native calf thymus DNA was also treated with methylmercury [CH3Hg(II)], an agent known to disrupt the secondary structure of DNA. The treatment yielded single-stranded methylmercurated DNA with preserved right-handed helix screwness. In addition, this DNA is digested by staphylococcal nuclease much more rapidly than double-stranded control DNA. Lastly, neither the CD nor the cleavage rate changes are reversible upon the removal of methylmercury.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

p53 and Ki-ras gene mutations in epithelial ovarian neoplasms.

In an effort to define the pathogenic relationship between ovarian neoplasms spanning the clinicopathological spectrum from benign to malignant, the incidence of Ki-ras and p53 mutations was determined in 20 ovarian cystadenomas, 20 low malignant potential (LMP) tumors of the ovary, and 23 ovarian carcinomas. Using DNA extracted from paraffin embedded tissue, polymerase chain reaction amplification, designed restriction fragment length polymorphism analysis, and DNA sequencing, 1 cystadenoma (5%), 6 LMP tumors (30%), and 1 ovarian carcinoma (4%) demonstrated an activated Ki-ras gene. All of the Ki-ras mutations identified except one were GGT to GAT transversions at codon 12. One LMP tumor demonstrated a CAA to CAC transversion at codon 61. Using polymerase chain reaction/single strand conformational polymorphism, DNA sequencing, and immunohistochemistry, 11 ovarian carcinomas (48%) demonstrated a p53 mutation. These mutations included 5 missense, 2 nonsense, and 1 frameshift mutation located within exons 6-8 and 3 mutations that were identified only by immunohistochemical staining. No p53 mutations could be identified in cystadenomas or LMP tumors. Clinically, the presence of either a Ki-ras or p53 mutation was associated with advanced stage disease. The pattern of Ki-ras and p53 mutations appears to distinguish LMP tumors from invasive carcinomas and suggests that they may be separate biological entities.

Adolescent↗
PubMed1993

Female twins with severe Christmas disease (hemophilia B).

Hemophilia B is an X-linked bleeding disorder. We report on female twins, who were conspicious in prolonged bleeding after venipuncture as well as hematomas after intramuscular injections even in the first months of their life. Their father suffering from a severe hemophilia B deceased in 1992. Their mother, half-brother and grandmother from their father's side had no signs of bleeding disorders. Clotting analysis performed in both twins revealed a markedly prolonged partial thromboplastin time (> 100 s). The factor IX levels were below 2%. In order to detect mutations, a general screen using the polymerase chain reaction (PCR) followed by single strand conformation polymorphism (SSCP) analysis of the PCR products have been performed. PCR products have been cut into smaller fragments using restriction endonucleases (RE) for an in-depth SSCP screen. A general screen for gross abnormalities in the factor IX gene including deletions, insertions and rearrangements was performed by Southern blot analysis of RE-digests of genomic DNA using the factor IX cDNA as a hybridization probe. Furthermore, we screened for mutations in the CG dinucleotides comprising part of RE-recognition sequences (exon 1, 2, 3, 4, 5, and 8). By all methods applied herein, no mutations have been detected in these twins. On the basis of our results the hemophilia B of these twins might be explained by extreme non-random lyonization.

Child, Preschool↗
PubMed1992

Intrahelical pseudoknots and interhelical associations mediated by mispaired human minisatellite DNA sequences in vitro.

The human minisatellite arrays, 33.6 and 33.15, consist of tandem reiterations of a 37-nucleotide (nt) and a 16-nt repeat unit sequence, respectively, both of which contain a majority of purine bases on one strand. Knot-like tertiary structures, which mapped to the cloned arrays, were observed by electron microscopy (EM) in homoduplex molecules produced by denaturation and reannealing in vitro. They result from a primary hybridization between misaligned repeat units of the array, forming a slipped-strand structure with staggered single-stranded DNA loops, followed by a secondary hybridization between repeat units in the two loops. Depending on the relative alignment of the loops when they hybridize, a particular form of intrahelical pseudoknot is produced. Theta-shaped, figure-of-eight, and bow-shaped structures were the most common conformational isomers observed in homoduplexes flattened into two dimensions during EM preparation. At the site of a bow-shaped structure, a conformation-dependent bend of approximately 60 degrees between the flanking DNA segments is induced; the other conformations generally do not deflect the line of the main DNA axis. Paired loops, similar to the bow-shaped structure, were apically situated in some supercoiled plasmids containing the 33.6 array. Both plasmids formed intermolecular associations, consisting of two (or more) homoduplex molecules held together at or immediately adjacent to a nexus which mapped to the minisatellite sequences. These associations might arise either by interhelical hybridization between arrays or by knot-like structures interfering with branch migration of chi-form Holliday junctions.

Base Sequence↗
PubMed1993

Chromosome 17p deletions and p53 mutations in renal cell carcinoma.

Studies of the role of tumor suppressor genes in human renal cell carcinoma from our laboratory have suggested the presence of a disease gene(s) on the short arm of chromosome 3. Little is known about the role other tumor suppressor genes may play in this malignancy. Abnormalities of chromosome 17p and, in particular of p53, are common in many human malignancies. In order to evaluate the role of this region in renal cell carcinoma, we performed restriction fragment length polymorphism analyses of chromosome 17 with probes localized to the p53 region. Fourteen of 29 (48%) evaluable cell lines showed loss of heterozygosity at this locus. Northern blot analysis did not detect a p53 transcript in 4 of 27 cell lines tested. In addition, we screened cell lines for p53 mutations using a polymerase chain reaction-single strand conformation polymorphism technique. Cell lines positive for mutations by this technique were then sequenced. Mutations were detected in 11 of 33 (33%) cell lines, including 8 derived from primary tumors and 3 derived from metastatic foci. Six of 9 (67%) patients with loss of heterozygosity demonstrated a mutation in the remaining allele, while only 1 of 8 (13%) without loss of heterozygosity had a mutation. Three of 3 (100%) cell lines derived from metastases had the same mutation as their matched primary cell line. Loss or mutation of p53 did not correlate either with loss of chromosome 3p or with histological subtype. These results suggest that, while the primary disease gene for kidney cancer appears to be on chromosome 3, abnormalities of p53 are common and may be involved in the progression of this malignancy.

Base Sequence↗
PubMed1994

Clinical implications of p53 gene mutation in the progression of Barrett's epithelium to invasive esophageal cancer.

The p53 tumor suppressor gene has been implicated in human esophageal tumorigenesis, and mutations are reported in primary esophageal adenocarcinomas and associated Barrett's epithelium. To evaluate the potential clinical significance of this molecular genetic marker in the progression of Barrett's epithelium to invasive esophageal cancer, we studied 20 patients with Barrett's epithelium, 10 of whom had an associated adenocarcinoma. p53 gene mutations were screened using polymerase chain reaction (PCR)/single-strand conformation polymorphism (SSCP) analysis and p53 oncoprotein distribution by immunohistochemistry. Point mutations were localized to exons 5 and 7 of the p53 gene, previously recognized as "hot spots." p53 gene mutations and immunoreactivity were detected in 7 of 10 patients with primary esophageal adenocarcinomas and in 6 patients with associated Barrett's epithelium, 3 of whom had high-grade dysplasia. Little correlation was observed between p53 positivity and clinicopathologic findings or outcome, although two patients with p53 mutations subsequently developed second primary cancers. Of 10 patients with Barrett's epithelium alone, 6 had p53 mutations, with mild or no dysplasia histologically, suggesting that p53 gene mutation may be an early event in progression to invasive cancer. No patient has developed invasive cancer to date, with a median follow-up of 8 years. These studies further implicate the p53 gene in the Barrett's epithelium-to-carcinoma sequence. Prospective surveillance studies incorporating molecular analysis of the p53 gene are warranted to further evaluate p53 as a predictor of patients at high risk for developing malignancy.

Adenocarcinoma↗
PubMed1992

The product of the human MUC1 gene when secreted by mouse cells transfected with the full-length cDNA lacks the cytoplasmic tail.

The polymorphic epithelial mucin (PEM) is found as a cell associated transmembrane protein with an extracellular domain made up largely of tandem repeats and also as a soluble form in some body fluids and culture supernatants. To determine whether the soluble form can arise without the mechanism of alternative splicing mouse cells have been transfected with an expression construct containing the full-length cDNA, and the supernatants of the transfectants analyzed for the presence of the mucin. The presence of mucin in the supernatants could indeed be detected in a radioimmunoassay and by immunoprecipitation using monoclonal antibodies to the tandem repeat region of the core protein, indicating that release of the soluble form can occur without alternative splicing. The soluble form was not however precipitated with a polyclonal antiserum to the cytoplasmic tail, suggesting that it was released from the membrane by the action of a protease.

Animals↗
PubMed1995

A Gly1127Ser mutation in an EGF-like domain of the fibrillin-1 gene is a risk factor for ascending aortic aneurysm and dissection.

Ascending aortic disease, ranging from mild aortic root enlargement to aneurysm and/or dissection, has been identified in 10 individuals of a kindred, none of whom had classical Marfan syndrome (MFS). Single-strand conformation analysis of the entire fibrillin-1 (FBN1) cDNA of an affected family member revealed a G-to-A transition at nucleotide 3379, predicting a Gly1127Ser substitution. The glycine in this position is highly conserved in EGF-like domains of FBN1 and other proteins. This mutation was present in 9 of 10 affected family members and in 1 young unaffected member but was not found in other unaffected members, in 168 chromosomes from normal controls, and in 188 chromosomes from other individuals with MFS or related phenotypes. FBN1 intragenic marker haplotypes ruled out the possibility that the other allele played a significant role in modulating the phenotype in this family. Pulse-chase studies revealed normal fibrillin synthesis but reduced fibrillin deposition into the extracellular matrix in cultured fibroblasts from a Gly1127Ser carrier. We postulate that the Gly1127Ser FBN1 mutation is responsible for reduced matrix deposition. We suggest that mutations such as this one may disrupt EGF-like domain folding less drastically than do substitutions of cysteine or of other amino acids important for calcium-binding that cause classical MFS. The Gly1127Ser mutation, therefore, produces a mild form of autosomal dominantly inherited weakness of elastic tissue, which predisposes to ascending aortic aneurysm and dissection later in life.

Adult↗
PubMed1993

Rapid and simple subtyping of the HLA-DRB3 gene in Graves' disease by using temperature-gradient gel electrophoresis.

A HLA-DRB3-subtyping system that uses TGGE for analyzing DRB3 alleles was developed. The polymorphic second exon of the HLA-DRB3 gene was amplified from four homozygous typing cell lines, 223 healthy individuals, and 102 patients with Graves' disease by using the PCR. The PCR products were electrophoresed in a temperature gradient from 35 degrees C to 70 degrees C, and the resulting fragments were visualized by silver staining. Four DRB3 alleles (HLA-DRB3*0101, *0201, *0202, and *0301) were distinguished from one another by the migration of the corresponding homoduplex with the exception that DRB3*0201 was indistinguishable from DRB3*0202. The latter two alleles, however, were resolved by the artificial heteroduplexing approach. Arginine in position 74 of the DRB3 gene product (i.e., HLA-DRB3*0101) was significantly more frequent in Graves' patients than in controls. The relative risk conferred by the presence of the DRB3*0101 was 15.8 (p < or = 0.001). The presence of arginine in position 74 contributed to an etiologic fraction of 75% in our study population. The PCR-TGGE technique is a simple, nonisotopic method, which may be useful in rapid screening of large populations for HLA disease markers.

Alleles↗
PubMed1995

Déjérine-Sottas neuropathy is associated with a de novo PMP22 mutation.

We identified a de novo mutation in the peripheral myelin protein (PMP22) gene of a patient with Déjérine-Sottas neuropathy. Single-stranded conformation analysis of PCR-amplified DNA fragments showed an additional fragment for exon 1 in the patient, which was absent in the unaffected parents. Sequence analysis showed a de novo point mutation C85-->A that results in an amino acid substitution His12Gln in the first transmembrane domain of PMP22. This provides further evidence that sporadic cases of Déjérine-Sottas neuropathy can be due to dominant single base substitutions.

Amino Acid Sequence↗
PubMed1995

Divalent zinc cations induce the formation of two distinct homoduplexes of a d(GA)20 DNA sequence.

Homopurine DNA sequences are highly structurally polymorphic. In particular, d(GA)n DNA sequences are known to be capable of forming intramolecular foldbacks, bimolecular homoduplexes, and tetrastranded complexes. Counterions play a determinant role on the equilibria between the different structural conformers of d(GA)n sequences. In this paper, the effect of divalent zinc cations on the structure of a d(GA)20 oligonucleotide has been analyzed by CD spectroscopy and polyacrylamide gel electrophoresis. Depending on the precise experimental conditions at which zinc is added, two distinct conformations of the d(GA)20 oligonucleotide are stabilized. At neutral pH in the absence of zinc, d(GA)20 is partially organized into intramolecular foldbacks and bimolecular homoduplexes [Casasnovas et al. (1993) J. Mol. Biol. 233, 671-681]. Under these conditions, addition of zinc results in the stabilization of the bimolecular homoduplex which is nonspecific for zinc since it is also stabilized by divalent magnesium cations, increasing ionic strength, or decreasing pH. Its CD spectrum is identical to that reported earlier for parallel-stranded d(GA)n homoduplexes [Rippe et al. (1992) EMBO J. 11, 3777-3786]. On the other hand, if zinc is added under conditions where the d(GA)20 oligonucleotide is exclusively single-stranded, a different bimolecular homoduplex appears which is only observed in the presence of zinc. The zinc-specific duplex melts cooperatively, and, in contrast to the nonspecific duplex, its thermostability is high. Transition from the nonspecific to the zinc-specific duplex is observed at high zinc concentrations or at high temperatures. The transition is cooperative. These results are discussed in the context of the specific cation effects on the formation of intramolecular R.R.Y triplexes at d(GA.TC)n DNA sequences.

Animals↗