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At least 1,117 records · Page 62Linked to original sources
PubMed2000

swi1 and swi3 perform imprinting, pausing, and termination of DNA replication in S. pombe.

The developmental program of cell-type switching of S. pombe requires a strand-specific imprinting event at the mating-type locus (mat1). Imprinting occurs only when mat1 is replicated in a specific direction and requires several trans-acting factors. This work shows (1) that the factors swi1p and swi3p act by pausing the replication fork at the imprinting site; and (2) that swi1p and swi3p are involved in termination at the mat1-proximal polar-terminator of replication (RTS1). A genetic screen to identify termination factors identified an allele that separated pausing/imprinting and termination functions of swip. These results suggest that swi1p and swi3p promote imprinting in novel ways both by pausing replication at mat1 and by terminating replication at RTS1.

Cell Cycle Proteins↗
PubMed1996

Germline BRCA1 185delAG mutations in Jewish women with breast cancer.

BACKGROUND: We aimed to find out the proportion of breast cancers in Ashkenazi Jewish women attributable to the frameshift mutation at position 185 involving the deletion of adenine and guanine (185delAG) in the breast cancer gene BRCA1. METHODS: We studied 107 Ashkenazi Jewish women with breast cancer seen at medical oncology and genetic counseling clinics in New York over a three and a half year period beginning in 1992. 80 of the women were diagnosed before age 42 years; the other 27 were diagnosed between 42 and 50 years and had a positive family history. Genomic DNA testing by PCR amplification was done to identify any 185delAG mutations of the BRCA1 gene. FINDINGS: Of the 80 women diagnosed before the age of 42 years, 16 (20%, 95% CI 11.2-28.8) were heterozygous for the mutation. All 16 women had at least one first-degree or second-degree relative with breast or ovarian cancer. Of 27 probands diagnosed with breast cancer between the ages of 42 and 50 years who had at least one first-degree relative affected with breast or ovarian cancer, 8 (30%, 95% CI 12-47) had 185delAG mutations. INTERPRETATION: These data suggest that screening for the 185delAG mutation may be useful in genetic counselling of these women where options for detection and prevention of possible cancers can be discussed.

Adult↗
PubMed2002

Simultaneous mapping of human papillomavirus integration sites and molecular karyotyping in short-term cultures of cervical carcinomas by using 49-color combined binary ratio labeling fluorescence in situ hybridization.

Infection with high-risk type human papillomavirus (HPV) is a necessary causal factor in the pathogenesis of cervical carcinoma. In most invasive cervical cancers, HPV is integrated in the host cell genome, and additional genetic aberrations are observed among which are chromosomal aberrations. To analyze in detail such often complex chromosomal changes and simultaneously map HPV integration sites, we extended the multiplicity of the combined binary ratio labeling fluorescence in situ hybridization (COBRA-FISH) technique to 49 by inclusion of a large Stokes' shift fluorochrome as the third binary label. The technique allows mapping of the integrated HPV genome in the context of p- and q-arm COBRA-FISH, with a sensitivity of one copy of the HPV genome as tested for HPV 16 in SiHa cells. We investigated the molecular karyotypes and integration patterns of HPV types 16 and 18 in metaphase spreads from short-term cultures of primary cervical carcinomas (n=5). Of the tested cervical carcinomas, two contained integrated HPV at 8q24, one of which in addition harbored the integrated virus near a translocation breakpoint. Two carcinomas had integrated HPV at 17q21 through 23 in a morphologically normal chromosome 17. One carcinoma contained HPV at 1q42 in a morphologically normal chromosome 1. Our data illustrate the efficacy of 49-color COBRA-FISH to resolve complex karyotypes and simultaneously map specific sequences in metaphases obtained from short-term solid tumor cultures.

Color↗
PubMed1998

Characterization of a chloroplast isoform of serine acetyltransferase from the thermo-acidiphilic red alga Cyanidioschyzon merolae.

We isolated a gene for serine acetyltransferase (SAT), a key enzyme in sulfate assimilation, from the primitive red alga Cyanidioschyzon merolae, an inhabitant of sulfurous hot springs, and designated this gene cmSAT. The N-terminal region of the cmSAT protein has characteristics of a chloroplast targeting peptide. cmSAT protein fused with a 6x histidine tag complemented a SAT deficient Escherichia coli mutant. The protein was purified with its SAT activity, which was inhibited by cysteine, using the high affinity of the histidine tag in an Ni-NTA column. The Km values for acetyl-CoA and l-serine were 0.3 and 0.1 mM, respectively. Southern blotting indicated the existence of other SAT isoforms in C. merolae. A 2.4 kb transcript was always detected when growth was synchronized under a 12-h light/dark cycle. Under these conditions, a 31-kDa protein was always detected on immunoblots, indicating processing of the cmSAT protein and constitutive expression of cmSAT. A 45-kDa protein, thought to be the unprocessed cmSAT protein, was detected in the dark period, from M phase to early G1 phase. No significant change in the level of protein expression was detected under continuous darkness or in a sulfate-deficient medium. Using immunoelectron microscopy, the cmSAT protein was primarily detected in the stroma and a few were detected in the cytoplasm, which indicate that cmSAT protein is transported to and functions in a chloroplast.

Acetyltransferases↗
PubMed1998

Germline screening of the NF-2 gene in families with unilateral vestibular schwannoma.

Vestibular schwannoma may present clinically in two forms: sporadic unilateral or hereditary bilateral. Familial transmission of vestibular schwannoma is known to occur only in neurofibromatosis type II (NF-2). We have previously described the clinical characteristics of unilateral vestibular schwannoma presenting in families, in the absence of ther criteria necessary for the diagnosis of NF-2. Polymerase chain reaction-single strand chain polymorphism was used to screen for germline NF-2 gene mutations in six families with unilateral vestibular schwannoma. Direct sequencing of DNA from blood was done in affected subjects from three families. No germline mutations were identified. Because NF-2 gene mutations are detected in only 33% of patients with NF-2, hereditary transmission of mutations cannot be entirely excluded. However, in the absence of germline mutations in the NF-2 gene, familial occurrence of unilateral vestibular schwannoma more likely represents either a chance somatic NF-2 gene mutation or originates from a separate genetic loci.

Case-Control Studies↗
PubMed2001

Anticipation, imprinting, trinucleotide repeat expansions and psychoses.

1. Since 1991, approximately 20 trinucleotide repeat expansion type neurodegenerative disorders have been reported. They are clinically characterized by anticipation, i.e., worsening severity or earlier age at onset with each succeeding generation for an inherited disease, and imprinting, i.e., a process whereby specific genes are differentially marked during parental gametogenesis, resulting in the differential expression of these genes in the embryo and adult. 2. The phenomenon of anticipation in psychoses has been pointed out since the 19th century; however, it was ignored because no one knew the genetic mechanism underlying this type of inheritance pattern at the time, and because of several possible biases. 3. The discovery of trinucleotide repeat expansion diseases has reawakened interest in the phenomenon of anticipation in psychiatric diseases. Anticipation has been confirmed in schizophrenia, mood disorders, and anxiety disorders in much more sophisticated manners, although still not perfectly. 4. Molecular approaches as well as clinical ones have been taken to reveal the involvement of trinucleotide repeat expansion mechanism in psychoses by means of direct analyses of candidate genes, RED and DIRECT. Most efforts have been made for CAG type trinucleotide repeats. So far, direct analyses have failed to reveal pathogenic gene(s). There were several positive RED data at first, however, nowadays there seems to be a tendency of much more negative results. The DIRECT results did not support trinucleotide repeat expansions mechanism in psychoses either. One plausable explanation for the 'false positive' result is the presence of CAG trinucleotide repeats which are highly polymorphic but not associated with an obvious abnormal phenotype. Screening for trinucleotide repeats other than ones of the CAG type remained to be performed.

Anticipation, Genetic↗
PubMed2001

Chromosomal sequences flanking an efficiently expressed transgene dramatically enhance its expression.

The expression of transgenes in mice is influenced strongly by their site of integration in the genome. To test whether the chromosomal sequences immediately flanking a site of integration could positively influence expression we isolated the 5' and 3' chromosomal sequences from an efficiently expressed transgenic locus. These chromosomal sequences were incorporated into transgene constructs and these were then introduced into mice. Linking them to the original transgene dramatically enhanced its expression and conferred a degree of position independent expression upon it. However, the results were not as marked when these sequences were linked to other constructs, showing that the effectiveness of such flanking chromosomal sequences is highly dependent on the nature of the transgene used.

Animals↗
PubMed1997

Identification of a profilin homologue in Trypanosoma brucei by complementation screening.

Using genetic complementation in Saccharomyces cerevisiae, we have isolated a Trypanosoma brucei gene encoding profilin. Overexpression of trypanosome profilin suppresses defects that are associated with the loss of the C-terminal domain of the adenylyl cyclase-associated protein in S. cerevisiae. Similarly, the T. brucei gene complements a profilin-deletion mutant of S. cerevisiae. The full-length cDNA clone isolated contains an open reading frame of 150 amino acids, with a predicted molecular mass of 16.1 kDa. The gene appears to be present at single copy and is expressed at approximately equal levels in both mammalian and insect forms of the parasite.

Amino Acid Sequence↗
PubMed2005

Complete gene scanning by temperature gradient capillary electrophoresis using the cystic fibrosis transmembrane conductance regulator gene as a model.

Many inherited diseases involve large genes with many different mutations. Identifying a wide spectrum of mutations requires an efficient gene-scanning method. By differentiating thermodynamic stability and mobility of heteroduplexes from heterozygous samples, temperature gradient capillary electrophoresis (TGCE) was used to scan the entire coding region of the cystic fibrosis transmembrane conductance regulator gene. An initial panel (29 different mutations) showed 100% agreement between TGCE scanning and previously genotyped results for heterozygous samples. Different peak patterns were observed for single base substitutions and base insertions/deletions. Subsequently, 12 deidentified clinical samples genotyped as wild type for 32 mutations were scanned for the entire 27 exons. Results were 100% concordance with the bidirectional sequence analysis. Ten samples had nucleotide variations including a reported base insertion in intron 14b (2789 + 2insA) resulting in a possible mRNA splicing defect, and an unreported missense mutation in exon 20 (3991 G/A) with unknown clinical significance. This methodology does not require labeled primers or probes for detection and separation through a temperature gradient eliminates laborious temperature optimization required for other technologies. TGCE automation and high-throughput capability can be implemented in a clinical environment for mutation scanning with high sensitivity, thus reducing sequencing cost and effort.

Cystic Fibrosis Transmembrane Conductance Regulato↗
PubMed2005

Tumor microsatellite instability in early onset gastric cancer.

Gastric cancer (GC) remains a leading cause of cancer mortality worldwide. Genetic factors are implicated, including DNA mismatch repair (MMR) deficiency manifested as tumor microsatellite instability (MSI). However, a standardized panel of markers and a definition of low-versus-high level MSI in GC are lacking. We examined a population-based cohort of early onset ( or=3 markers MSI+/MSI-high) demonstrated MMR protein deficiency. Three novel hMLH1 mutations (two germline frameshift and one somatic nonsense) were also found. The only significant clinicopathological associations were increased tumor size in MSI+ cases (P=0.04) and Lauren histotype (P=0.006) and tumor grade (P=0.007) in MSI-high cases. Tumor size, location, depth, nodal status, and Ming subtype were significant prognostic variables. Therefore, we propose a new definition of high-level MSI based on unifying characteristics of instability of more than or equal to three of six mononucleotide markers and loss of MMR protein expression.

Adaptor Proteins, Signal Transducing↗
PubMed2003

The search for type 2 diabetes genes.

Type 2 diabetes (T2DM) is a serious disease with severe complications. Around one in 10 people alive today suffer from type 2 diabetes or are destined to develop it before they die. Inheritance plays an important role in the cause of type 2 diabetes. A considerable amount of research is devoted to defining the genes involved in the aetiology of this widespread disease. This information is crucial if we are to improve our methods of preventing and treating diabetes. Over the last 25 years there have been considerable advances in our understanding of the genetics of diabetes. Important discoveries have been made in dissecting the genes involved in rare monogenic forms of type 2 diabetes which has become a paradigm for genetic studies of type 2 diabetes. This review focuses on the main approaches currently adopted and our current understanding of the genes involved in susceptibility to type 2 diabetes.

Diabetes Mellitus, Type 2↗
PubMed2003

A genomewide screening of N-ethyl-N-nitrosourea-mutagenized mice for musculoskeletal phenotypes.

Chemical mutagenesis followed by screening for abnormal phenotypes in the mouse holds much promise as a method for revealing gene function. We describe a mouse N-ethyl-N-nitrosourea (ENU) mutagenesis program incorporating a genomewide screen of dominant as well as recessive mutations affecting musculoskeletal disorders in C3H/HeJ mice. In a primary screen, progeny of one-generation dominant mutations (F(1)) and three-generation recessive (F(3)) mutations were screened at 10 weeks of age for musculoskeletal disorders using dual-energy X-ray absorptiometery (DEXA) and biochemical markers affecting bone metabolism, such as osteocalcin, type I collagen breakdown product, skeletal alkaline phosphatase, and insulin-like growth factor I (IGF-I). Abnormal phenotypes were identified as +/-3SD units different from baseline data collected from age- and sex-matched nonmutagenized control mice. A secondary screen at 16 weeks of age, which included peripheral quantitative computed tomography (pQCT) in addition to those parameters described in our primary screen, was used to confirm the abnormal phenotypes observed in the primary screen. The phenodeviant or outlier mice were progeny tested to determine whether their abnormality segregates bimodally in their offspring with the expected 1:1 or 1:3 Mendelian ratio, in dominant and recessive screens, respectively. With the above screening strategy, we were able to identify several mice with quantitative abnormalities in BMD, BMC, bone size, and bone metabolism. We have progeny tested and confirmed four outliers with low BMD, low bone size, and growth-related abnormality. Our results indicate that the magnitude of change in quantitative phenotypes in the ENU-mutagenized progeny was between 10 and 15%, and hence, the yield of outliers was dependent on the precision of the methods. So far, this ENU mutagenesis program has identified four outliers that can undergo positional cloning.

Alkaline Phosphatase↗
PubMed1999

STK11/LKB1 germline mutations are not identified in most Peutz-Jeghers syndrome patients.

Germline mutations of the STK11 gene mapped to chromosome 19p13.3 are responsible for Peutz Jeghers syndrome (PJS), a dominant disorder associated with characteristic gastrointestinal hamartomatous polyps and a predisposition to various cancers. We conducted a detailed investigation of germline STK11 alterations by protein truncation test and genomic DNA sequence analysis in ten unrelated PJS families. We identified a novel truncating deletion spanning STK11 exons 2-7 in a single patient and several known polymorphisms. Loss of heterozygosity studies in PJS polyps of four of these patients identified an allelic deletion of D19S886 in another patient. Our results suggest that STK11 mutations account for only a proportion of PJS cases.

AMP-Activated Protein Kinase Kinases↗