Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “frameshift mutation”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,747 records · Page 97Linked to original sources
PubMed1998

An L-type calcium-channel gene mutated in incomplete X-linked congenital stationary night blindness.

The locus for the incomplete form of X-linked congenital stationary night blindness (CSNB2) maps to a 1.1-Mb region in Xp11.23 between markers DXS722 and DXS255. We identified a retina-specific calcium channel alpha1-subunit gene (CACNA1F) in this region, consisting of 48 exons encoding 1966 amino acids and showing high homology to L-type calcium channel alpha1-subunits. Mutation analysis in 13 families with CSNB2 revealed nine different mutations in 10 families, including three nonsense and one frameshift mutation. These data indicate that aberrations in a voltage-gated calcium channel, presumably causing a decrease in neurotransmitter release from photoreceptor presynaptic terminals, are a frequent cause of CSNB2.

Amino Acid Sequence↗
PubMed1998

A gonococcal porA pseudogene: implications for understanding the evolution and pathogenicity of Neisseria gonorrhoeae.

Members of the genus Neisseria, including the human pathogens Neisseria meningitidis and Neisseria gonorrhoeae, express at least one member of a family of related porins. N. meningitidis is the only species known to express a second porin, the meningococcal serosubtyping antigen PorA, the most divergent member of this family. Unexpectedly, a porA gene was identified in the gonococcal genome. Both the gonococcal and meningococcal porA loci were adjacent to a homologue of the Escherichia coli greA gene, although the IS1106 element downstream of porA in some meningococci was absent in the gonococcus. Almost identical porA loci were present in four unrelated gonococcal isolates and clinical specimens from patients with gonorrhoea. Lack of PorA expression in the gonococcus resulted from mutations in the promoter region, which prevented transcription, and frameshift mutations in the coding region of the porA gene. Hybridization and amplification experiments, showing the absence of a porA gene in seven other Neisseria species, suggested that porA was acquired by a common ancestor of the gonococcus and meningococcus but inactivated in the gonococcus on speciation. This implies that, while advantageous during colonization of the upper respiratory tract, this protein has no function in, or hinders, colonization of the urogenital tract.

Amino Acid Sequence↗
PubMed2002

Congenital myasthenic syndrome (CMS) in three European kinships due to a novel splice mutation (IVS7 - 2 A/G) in the epsilon acetylcholine receptor (AChR) subunit gene.

Mutations in the epsilon-acetylcholine receptor (AChR epsilon) subunit gene cause congenital myasthenic syndromes (CMS) with postsynaptic neural transmission defects. We present 3 male and 2 female patients from three unrelated Croatian, Hungarian, and Russian families with autosomal recessive CMS. All patients manifested with variable degrees of ophthalmoparesis and generalized, fatiguable muscle weakness since birth or early infancy. Electrophysiological studies showed a decremental response in all patients indicating a neuromuscular transmission defect. Pyridostigmine treatment improved the proximal muscle weakness whereas the ophthalmoparesis remained unchanged in all patients. Analysis of the AChR epsilon subunit gene showed homozygosity for a novel splice site mutation of intron 7 epsilon(IVS7-2A/G) in the two Croatian siblings. epsilon-mRNA analysis by RT-PCR and direct sequencing revealed that exon 7 was spliced directly to exon 9 with skipping of exon 8. The Hungarian and Russian patients were heteroallelic carriers of the same mutation epsilon(IVS7-2A/G) and of a frameshifting mutation epsilon 70insG and epsilon 1293insG, respectively. We hypothesize that altered splice products may not be expressed as functional receptors at the cell surface. A haplotype analysis with polymorphic markers revealed a high degree of similarity for the epsilon(IVS7-2A/G) carrying allele in all families and may therefore indicate a common origin of the mutation.

Adolescent↗
PubMed1987

The specificity of UV-induced mutations at an endogenous locus in mammalian cells.

We have used a rapid in vivo recombinational method to clone and completely sequence 34 UV-induced mutants at the adenine phosphoribosyltransferase (APRT) locus of Chinese hamster ovary cells. Among the mutants recovered, 26 were single base substitutions including 17 G.C----A.T transitions and a single A.T----G.C transition. Three of the 4 possible transversions accounted for the remaining 8 mutations. The G.C----T.A transversion was not recovered. Six tandem double or closely neighboring double-base substitutions, one double mutation consisting of a G.C----T.A transversion and an adjacent frameshift, as well as one single frameshift mutation were also recovered. UV-induced mutation appears to be targeted to dipyrimidine sites with only two exceptions. These include two double mutations where only one of the base substitutions occurred at a dipyrimidine site. The observed specificity of UV-light-induced mutations at the APRT locus is consistent with the argument that G.C----A.T transitions result primarily from the (6-4) pyrimidine pyrimidone lesion. A striking resemblance in the distribution of UV-induced mutants and a collection of 30 spontaneous mutants identified recently in our laboratory was noted. Both share a common strong site of multiple occurrence and a considerable degree of overlap with respect to site specificity. We speculate therefore that DNA context plays a significant role in mutation fixation in mammalian cells.

Adenine Phosphoribosyltransferase↗
PubMed1994

Pyruvate dehydrogenase deficiency. Clinical presentation and molecular genetic characterization of five new patients.

Fibroblast cultures from five patients with early onset severe encephalopathy and lactic acidosis were studied for evidence of pyruvate dehydrogenase (PDH) deficiency. Three males had significantly reduced activity (0.29-0.45 nmol/mg protein/min versus normal controls 0.7-1.1 nmol/mg protein/min); two females had PDH activity within the normal range. However, as the majority of cases of PDH deficiency result from defects in the X-linked E1 alpha subunit and both females had biased patterns of X-inactivation (making it impossible to rule out the possibility that they were heterozygous for an E1 alpha gene defect) molecular genetic studies were performed. cDNA from the male patients was sequenced and mis-sense mutations found: Y243N (T-->A) in exon 7, D315A (G-->A) in exon 10 and R378H (G-->A) in exon 11. Single-strand conformation polymorphism analysis of amplified genomic DNA fragments and sequencing revealed a mis-sense mutation M282L (A-->C) in one female and a frameshift mutation caused by insertion of T (R288ins) in the other. Adding to recent descriptions of new mutations, this report emphasizes the allelic heterogeneity of the condition. The identification of mutations in females with a suggestive clinical phenotype, even when peripheral fibroblasts do not show deficient PDH activity, illustrates the importance of molecular analysis of this disease.

Base Sequence↗
PubMed2001

Clinical, electrophysiological and molecular genetic characteristics of 93 patients with X-linked Charcot-Marie-Tooth disease.

X-linked dominant Charcot-Marie-Tooth (CMTX) disease is a motor and sensory neuropathy caused by mutations in the connexin 32 (CX32) gene. In this study we report the clinical, electrophysiological and genetic features of 93 patients (41 males, 52 females) from 37 unrelated families with CMTX. Age at onset was 15.4 +/- 9.6 years in males (range 1-40 years) and 18.7 +/- 13.1 years in females (range 1-56 years) (P = 0.22) and the duration of disease at the time of examination was 18.3 +/- 14.6 years in males and 23.9 +/- 13.7 years in females (P = 0.11). Males were more severely affected than females, with significantly more frequent muscle weakness, amyotrophy, proprioception loss, upper limb areflexia and pes cavus. Females were more frequently asymptomatic, whereas high functional disability scores were more frequently encountered in males. The electrophysiological studies showed that motor nerve conduction velocities in CMTX females, but not males, were heterogeneous between nerves compared with Charcot-Marie-Tooth type 1A (CMT1A) patients and controls. The terminal latency index (TLI) for the median nerve was 0.37 +/- 0.08; it was similar in men and in women and a little higher than those observed in CMT1A and controls. The range of values for median TLI was wider in both male and female CMTX patients than in controls, but was similar to that of CMT1A patients, suggesting that motor conduction was relatively homogeneous within a given nerve. Twenty-seven different CX32 mutations, including missense (n = 23), nonsense (n = 2) and frameshift mutations (n = 1) and one entire deletion of the CX32 coding sequence, were observed in the 37 families. Four of these mutations are described for the first time. The phenotype of the patients, especially age at onset, is discussed in relation to the functional consequences of CX32 mutations, analysed in vitro in Xenopus oocytes and mammalian cells. CMTX patients with age at onset in the first decade mostly presented non-functional mutations, suggesting that the physiological consequences of the mutations affect age at onset in CMTX.

Adolescent↗
PubMed1993

p53 mutations in phenacetin-associated human urothelial carcinomas.

Chronic abuse of the analgesic drug phenacetin is associated with an increased risk of development of transitional cell carcinomas of the urinary tract. It is unclear whether phenacetin acts through chronic tissue damage (phenacetin nephropathy) or via a genotoxic metabolite causing promutagenic DNA lesions. In the present study, we investigated 15 urothelial carcinomas from 13 patients with evidence of phenacetin abuse. Tumors were screened for p53 mutations in exons 5-8 by single-strand conformation polymorphism (SSCP) analysis, followed by direct sequencing of PCR-amplified DNA. p53 Mutations were detected in 8/14 primary tumors (57%). All except one were missense mutations located in exon 5 (three mutations), exon 6 (one), exon 7 (two) and exon 8 (one). The type of mutation varied, with a preference for CpG sites. A frameshift mutation resulting from the insertion of a single cytosine at codons 151/152 was detected in a bladder tumor and its lung metastasis. Urothelial carcinomas located in the renal pelvis and in the ureter of the same patient exhibited two different mutations, strongly suggesting that they developed independently. Another patient had tumors in the renal pelvis and bladder, both of which contained the same p53 mutation, indicating intracavitary metastatic spread. This demonstrates that screening of p53 mutations allows the clonal origin of tumors in patients with multiple primary and metastatic lesions to be determined. None of the tumors investigated contained mutations in codons 12, 13 or 61 of H-ras or K-ras protooncogenes.

Aged↗
PubMed1993

Fucosidosis: four new mutations and a new polymorphism.

Fucosidosis is a rare lysosomal storage disease due to a nearly complete deficiency of alpha-L-fucosidase (EC 3.2.1.51). In this study, all 8 exons of the alpha-L-fucosidase structural gene (FUCA-1) were amplified by PCR methods, and the amplified products were subcloned and sequenced. Five patient groups with fucosidosis were selected according to their ethnic backgrounds and haplotypes for RFLPs in FUCA-1. Four presumptive disease causing mutations were detected: 1) A major deletion of DNA containing the last two exons of FUCA-1 in two Algerian siblings. 2) A G to T mutation in exon 6 resulting in an in-frame termination codon (E375X) in eight Hispanic patients from Colorado and New Mexico. 3) A G to A mutation (G60D) in exon 1 in four Italian patients and in three related French-American (Cajun) patients. This G60D mutation creates a unique site for AflIII. 4) A frameshift mutation resulted from a two-base deletion in exon 2 (K151fs) in an Italian patient. This deletion obliterates a unique BstXI site and creates a new BpmI site, and was found in only this patient and in only one allele. The rationale for proposing these defects as disease causing mutations includes pedigree analysis and the predicted consequences of each defect upon the activity and the concentration of the enzyme. An A to G transition (Q281R) in exon 5 was found to be present in homozygous form in affected patients and also in normal subjects; it appears to be a newly identified polymorphism. It causes a charge change and may be responsible for the electrophoretic variant phenotype of fucosidosis.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1999

Establishment and characterization of human laryngeal squamous cell carcinoma cell lines.

OBJECTIVES: Six human laryngeal squamous cell carcinoma cell lines (SNU-46, -585, -899, -1066, -1076, -1214) established from Korean patients are reported. STUDY DESIGN: In vitro culture of six squamous cell carcinoma cell lines derived from primary tumors of the larynx. Description of the cell line phenotypes and determination of molecular characteristics. METHODS: Six laryngeal squamous cell carcinoma cell lines were cultured. The cell phenotypes, including the histopathology of the primary tumors and in vitro growth characteristics, were determined. Molecular characterization was also performed, including DNA fingerprinting analysis and abnormalities of p15, p16, p53, and TGF-betaRII genes by polymerase chain reaction-based single strand conformation polymorphism and sequencing analysis. RESULTS: All cell lines grew as adherent cells; five lines grew as monolayers and one other line grew as stratifying colonies. All lines showed 1) high viability (75%-92%) with various doubling times (36-96 h); 2) absence of Mycoplasma and other bacteria; and 3) genetic heterogeneity by DNA profile analysis. p53 Mutations were found in three lines and p16 mutations were observed in five cell lines. TGF-betaRII mutations were found in two lines: one line had frameshift mutation and another line had a missense mutation at the kinase domain. CONCLUSIONS: These newly established and characterized laryngeal squamous cell carcinoma cell lines will be useful for investigating the biologic characteristics of laryngeal cancer.

Carcinoma, Squamous Cell↗
PubMed2004

Electroretinographic findings in patients with Stargardt disease and fundus flavimaculatus.

PURPOSE: To characterize the clinical and electroretinogram (ERG) features of our cohort of patients with Stargardt disease (STGD) exhibiting coding sequence variations in the ABCA4 gene. METHODS: Review of 76 patients with the clinical diagnosis of Stargardt disease/fundus flavimaculatus (STGD/FF) from the University of Iowa Department of Ophthalmology and Visual Sciences (41 patients) and the Casey Eye Institute (35 patients). Clinical examination, Goldmann perimetry, and electroretinography were performed on all 76 patients. Patients were divided into three groups on the basis of their funduscopic and electroretinographic features: (1) a normal ERG by the standards of the laboratory; (2) minimal rod or cone abnormalities; (3) severe ERG dysfunction. The latter category was further subdivided on the basis of a cone-dominated loss of function (C > R or "cone-rod dystrophy") or diffuse depression of rods and cones (C = R). Mutational analysis of the coding sequence of the ABCA4 gene was performed by single strand conformation polymorphism analysis followed by automated DNA sequencing. Each electroretinographic group was analyzed for the presence of disease causing changes using exact tests of binomial proportions corrected for multiple comparisons by Bonferroni method. Quantitative polymerase chain reaction (QPCR) was performed on patients who were homozygous for disease causing changes in the ABCA4 gene to rule out the possibility of deletions. RESULTS: Overall, 56 of 76 patients (and 77 of 152 alleles) exhibited coding sequence variations that were compatible with high-penetrance disease-causing mutations. The most common of these were His423Arg (9), frameshift mutations (7), Ala1038Val (7), and Pro1380Leu (6). Although no patients with His423Arg presented with normal ERGs, no significant correlation was observed between specific sequence variations and the electroretinographic characteristics or fundus appearance. However, a significantly greater fraction of patients with normal ERG studies failed to exhibit detectable disease-causing coding sequence variations in the ABCA4 gene identified on either allele (P = 0.0006). CONCLUSION: STGD/FF patients in our cohort exhibit a wide range of electroretinographic abnormalities, some of which are more prevalent than previously suspected. No direct correlation between clinical appearance, electrophysiologic characteristics and specific ABCA4 alleles could be identified, although a significantly lower number of our cohort with a normal ERG exhibited detectable coding sequence variations in the ABCA4 gene. However, four patients with ERG dysfunction were homozygous for a His423Arg change proven by QPCR not to be an artifact of a deletion. The presence of electrophysiologic dysfunction is not uncommon in our cohort of patients with STGD. Thus, the ERG provides clinically important information of retinal function for STGD/FF and, as such, is still indicated as part of the evaluation of these patients.

ATP-Binding Cassette Transporters↗
PubMed1999

PTEN/MMAC1 mutations in hepatocellular carcinomas: somatic inactivation of both alleles in tumors.

Allelic loss of loci on chromosome 10q occurs frequently in hepatocellular carcinomas. Somatic mutations of the PTEN/MMAC1 gene on this chromosome at 10q23 were recently identified in sporadic cancers of the uterus, brain, prostate and breast. To investigate the potential role of PTEN/MMAC1 gene in the genesis of hepatocellular carcinomas, we examined 96 tumors for allelic loss on 10q and also for subtle mutations anywhere within the coding region of PTEN/MMAC1 gene. Allelic loss was identified in 25 of the 89 (27%) tumors that were informative for polymorphic markers in the region. Somatic mutations were identified in five of those tumors: three frameshift mutations, a 1-bp insertion at codon 83-84 in exon 4 and two 4-bp deletions, both at codon 318-319 in exon 8; two C-to-G transversion mutation, both at -9 bp from the initiation codon in the 5' non-coding region of exon 1. No missense mutation was observed in this panel of tumors. In most of the informative tumors carrying intragenic mutations of one allele, we were able to detect loss of heterozygosity as well. These findings suggest that two alleles of the PTEN/MMAC1 gene may be inactivated by a combination of intragenic point mutation on one allele and loss of chromosomal material on the other allele in some of these tumors.

Alleles↗
PubMed1999

The physiological contribution of Acinetobacter PcaK, a transport system that acts upon protocatechuate, can be masked by the overlapping specificity of VanK.

VanK is the fourth member of the ubiquitous major facilitator superfamily of transport proteins to be identified that, together with PcaK, BenK, and MucK, contributes to aromatic catabolism in Acinetobacter sp. strain ADP1. VanK and PcaK have overlapping specificity for p-hydroxybenzoate and, most clearly, for protocatechuate: inactivation of both proteins severely impairs growth with protocatechuate, and the activity of either protein alone can mask the phenotype associated with inactivation of its homolog. Furthermore, vanK pcaK double-knockout mutants appear completely unable to grow in liquid culture with the hydroaromatic compound quinate, although such cells on plates convert quinate to protocatechuate, which then accumulates extracellularly and is readily visible as purple staining. This provides genetic evidence that quinate is converted to protocatechuate in the periplasm and is in line with the early argument that quinate catabolism should be physically separated from aromatic amino acid biosynthesis in the cytoplasm so as to avoid potential competition for intermediates common to both pathways. Previous studies of aromatic catabolism in Acinetobacter have taken advantage of the ability to select directly strains that contain a spontaneous mutation blocking the beta-ketoadipate pathway and preventing the toxic accumulation of carboxymuconate. By using this procedure, strains with a mutation in structural or regulatory genes blocking degradation of vanillate, p-hydroxybenzoate, or protocatechuate were selected. In this study, the overlapping specificity of the VanK and PcaK permeases was exploited to directly select strains with a mutation in either vanK or pcaK. Spontaneous mutations identified in vanK include a hot spot for frameshift mutation due to contraction of a G6 mononucleotide repeat as well as point mutations producing amino acid substitutions useful for analysis of VanK structure and function. Preliminary second-site suppression analysis using transformation-facilitated PCR mutagenesis in one VanK mutant gave results similar to those using LacY, the prototypic member of the major facilitator superfamily, consistent with the two proteins having a similar mechanism of action. The selection for transport mutants described here for Acinetobacter may also be applicable to Pseudomonas putida, where the PcaK permease has an additional role in chemotaxis.

Acinetobacter↗
PubMed2006

Somatic VHL gene alterations in MEN2-associated medullary thyroid carcinoma.

BACKGROUND: Germline mutations in RET are responsible for multiple endocrine neoplasia type 2 (MEN2), an autosomal dominantly inherited cancer syndrome that is characterized by medullary thyroid carcinoma (MTC), pheochromocytoma, and parathyroid hyperplasia/adenoma. Recent studies suggest a "second hit" mechanism resulting in amplification of mutant RET. Somatic VHL gene alterations are implicated in the pathogenesis of MEN2 pheochromocytomas. We hypothesized that somatic VHL gene alterations are also important in the pathogenesis of MEN2-associated MTC. METHODS: We analyzed 6 MTCs and 1 C-cell hyperplasia (CCH) specimen from 7 patients with MEN2A and RET germline mutations in codons 609, 618, 620, or 634, using microdissection, microsatellite analysis, phosphorimage densitometry, and VHL mutation analysis. RESULTS: First, we searched for allelic imbalance between mutant and wild-type RET by using the polymorphic markers D10S677, D10S1239, and RET on thyroid tissue from these patients. Evidence for RET amplification by this technique could be demonstrated in 3 of 6 MTCs. We then performed LOH analysis using D3S1038 and D3S1110 which map to the VHL gene locus at 3p25/26. VHL gene deletion was present in 3 MTCs. These 3 MTCs also had an allelic imbalance between mutant and wild-type RET. Mutation analysis of the VHL gene showed a somatic frameshift mutation in 1 MTC that also demonstrated LOH at 3p25/26. In the 2 other MTCs with allelic imbalance of RET and somatic VHL gene deletion, no somatic VHL mutation could be detected. The CCH specimen did neither reveal RET imbalance nor somatic VHL gene alterations. CONCLUSION: These data suggest that a RET germline mutation is necessary for development of CCH, that allelic imbalance between mutant and wild-type RET may set off tumorigenesis, and that somatic VHL gene alterations may not play a major role in tumorigenesis of MEN2A-associated MTC.

Carcinoma, Medullary↗
PubMed2002

Melanocortin 4 receptor sequence variations are seldom a cause of human obesity: the Swedish Obese Subjects, the HERITAGE Family Study, and a Memphis cohort.

The prevalence of mutations within and in the flanking regions of the gene encoding the melanocortin 4 receptor was investigated in severely obese and normal-weight subjects from the Swedish Obese Subjects study, the Health, Risk Factors, Exercise Training, and Genetics (HERITAGE) Family study, and a Memphis cohort. A total of 433 white and 95 black subjects (94% females) were screened for mutations by direct sequencing. Three previously described missense variants and nine novel (three missense, six silent) variants were detected. None of them showed significant association with obesity or related phenotypes. In addition, two novel deletions were found in two heterozygous obese women: a -65_-64delTG mutation within the 5' noncoding region and a 171delC frameshift mutation predicted to result in a truncated nonfunctional receptor. No pathogenic mutations were found among obese blacks or nonobese controls. Furthermore, none of the null mutations found in other populations was present in this sample. In conclusion, our results do not support the prevailing notion that sequence variation in the melanocortin 4 receptor gene is a frequent cause of human obesity.

5' Untranslated Regions↗
PubMed2001

Combined pituitary hormone deficiency caused by compound heterozygosity for two novel mutations in the POU domain of the Pit1/POU1F1 gene.

The POU homeodomain containing transcriptional activator POU1F1, formerly called Pit1 or GHF-1, is required for the embryological determination and postnatal secretory function of the GH-, PRL-, and TSH-producing cells in the anterior pituitary. Several mutations in the gene encoding POU1F1 have been described, resulting in a syndrome of combined pituitary hormone deficiency involving these three hormones. Most of the patients with this phenotype have either a dominant negative mutation in codon 271 (R271W) or are homozygous for a recessive mutation in the POU1F1 gene; to date only one case has been reported with compound heterozygosity for two point mutations. Here, we describe a boy with severe deficiencies of GH, PRL, and TSH who had compound heterozygosity for two novel point mutations in the POU1F1 gene: a 1-bp deletion frameshift mutation (747delA), the first one described to date in this gene, which leads to a nonfunctional truncated protein lacking the entire DNA recognition helix of the POU homeodomain, and a missense mutation in the C-terminal end of the fourth alpha-helix of the POU-specific domain (W193R),which causes a 500-fold reduction in the ability to bind to DNA and activate transcription.

Cell Line↗
PubMed1999

Germline MEN1 mutations in sixteen Japanese families with multiple endocrine neoplasia type 1 (MEN1).

OBJECTIVE: Multiple endocrine neoplasia type 1 (MEN1) is a syndrome of endocrine tumors involving the parathyroids, anterior pituitary and enteropancreatic neuroendocrine tissues, and is inherited in an autosomal dominant manner. Recently, the gene responsible for this syndrome, MEN1, was positionally cloned in 11q13. We aimed to assess the significance of MEN1 gene diagnostics in families with MEN1. DESIGN: Sixteen probands of familial MEN1 and their 40 family members were subjected to the study. METHODS: Full-length sequencing of the open reading frame and exon-intron boundaries in the MEN1 gene was performed with probands of familial MEN1. Family members were examined for the identified mutation in the proband. RESULTS: We identified heterozygous germline mutations of the MEN1 gene in all of 16 Japanese MEN1 families examined, achieving the highest detectability of MEN1 mutations in familial MEN1 among studies that examined more than 10 families. Eleven kinds of the identified MEN1 germline mutations were novel. More than half were nonsense or frameshift mutations resulting in a premature stop codon (9/15; 60%), and no mutation hot spots or no apparent genotype-phenotype relationships were observed, in support of the results of other studies. We identified 40 mutant MEN1 gene carriers and 16 non-carriers in the course of the present study in those families. CONCLUSIONS: Analysis of the germline mutations in the MEN1 gene, providing significantly useful clinical information to probands and family members of MEN1, should be considered as a standard procedure and categorized as belonging to Group 1 cancer predisposition testing by the American Society of Clinical Oncology.

Adult↗
PubMed1999

Dyskeratosis congenita caused by a 3' deletion: germline and somatic mosaicism in a female carrier.

X-linked dyskeratosis congenita (DC) is a bone marrow failure syndrome caused by mutations in the DKC1 gene located at Xq28. By 20 years of age, most affected boys develop bone marrow failure, whereas female carriers show a skewed pattern of X-chromosome inactivation. The gene product, dyskerin, is homologous to a yeast protein involved in ribosomal RNA biogenesis, providing a unique insight into a cause of aplastic anemia. Whereas most causative mutations are single amino acid substitutions, and nonsense or frameshift mutations have not been observed, we present here a case of DC caused by a 2-kb deletion that removes the last exon of the gene. Normal levels of mRNA are produced from the deleted gene, with the transcripts using a cryptic polyadenylation site in the antisense strand of the adjacent MPP1 gene, normally located 1 kb downstream of DKC1 in a tail to tail orientation. The predicted truncated protein lacks a lysine-rich peptide that is less conserved than the rest of the dyskerin molecule and is dispensable in yeast, supporting the contention that it may retain some activity and that null mutations at this locus may be lethal. The affected boy had an unaffected brother with the same haplotype around the DKC1 gene and a sister who was heterozygous for the deletion. We conclude therefore that the mother must be a germline mosaic with respect to this deletion. Investigation of her blood cells and other somatic tissues showed that a small proportion of these cells also carried the deletion, making her a somatic mosaic and indicating that the deletion took place early in development.

3' Untranslated Regions↗
PubMed1992

[Identification of two different genetic mutation associated with silent phenotypes for human serum cholinesterase in Japanese].

Two different gene mutations associated with the silent phenotype for human serum cholinesterase were demonstrated. DNA from five individuals with silent gene phenotype of three unrelated Japanese families was amplified by the polymerase chain reaction (PCR) and analyzed by direct sequencing. The first instance demonstrated a G----C transversion at codon 365 from GGA (Gly) to CGA (Arg), which was seen in three individuals of the two families. This mutation was resulted to create a new Taq 1 restriction site (TCGA). The second mutation was shown by a double heterozygous condition with two different silent gene mutations in two members of remaining one family. These mutations were as follows: 1) one type was a frameshift mutation, in which an extra A was inserted in codon 315 (ACC----AACC) to create a new stop codon at position 322 and 2) the other was the same point mutation at codon 365 as seen in the first instance. These results indicated that many silent variants can be distinguished by direct sequence analyses of genomic DNA.

Asian People↗