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Identification of an invasion-inducing gene, Tiam-1, that encodes a protein with homology to GDP-GTP exchangers for Rho-like proteins.

Using proviral tagging in combination with in vitro selection for invasiveness, we have identified a gene, designated Tiam-1, that affects invasion. In the selected invasive T lymphoma variants, proviral insertions were found within coding exons of the Tiam-1 gene, resulting in both truncated 5'-end and 3'-end transcripts that give rise to N- and C-terminal Tiam-1 protein fragments. In one invasive variant, amplification of the Tiam-1 locus was observed with concomitant increase in the amount of normal Tiam-1 protein. Cell clones that were invasive in vitro produced experimental metastases in nude mice, and transfection of truncated Tiam-1 cDNAs into noninvasive cells made these cells invasive. The predicted Tiam-1 protein harbors a Dbl- and Pleckstrin-homologous domain, which it shares with GDP-GTP exchangers for Rho-like proteins that have been implicated in cytoskeletal organization.

Amino Acid Sequence↗

Isolation of a thermostable enzyme variant by cloning and selection in a thermophile.

We developed a method for rapidly generating thermostable enzyme variants. Our strategy is to introduce the gene coding for a given enzyme from a mesophilic organism into a thermophile, Bacillus stearothermophilus. Variants that retain the enzymatic activity at the higher growth temperatures of the thermophile are then selected. This strategy was applied to kanamycin nucleotidyltransferase, which confers resistance to the antibiotic kanamycin. B. stearothermophilus carrying the wild-type enzyme is resistant to the antibiotic at 47 degrees C but not at 55 degrees C and above. Variants that were kanamycin resistant at 63 degrees C were obtained by selection of spontaneous mutants, by passage of a shuttle plasmid through the Escherichia coli mutD5 mutator strain and introduction into B. stearothermophilus by transformation, and by growing the thermophile in a chemostat. The kanamycin nucleotidyltransferases purified from these variants were all more resistant to irreversible thermal inactivation than is the wild-type enzyme, and all have the same single amino acid replacement, aspartate to tyrosine at position 80. Mutants that are even more heat stable were derived from the first variant by selecting for kanamycin resistance at 70 degrees C, and these carry the additional change of threonine to lysine at position 130. This strategy is applicable to other enzymatic activities that are selectable in thermophiles or that can be screened for by plate assays.

Bacillus subtilis↗

The risk of bleeding complications in patients with cytochrome P450 CYP2C9*2 or CYP2C9*3 alleles on acenocoumarol or phenprocoumon.

The principal enzyme involved in coumarin metabolism is CYP2C9. Allelic variants of CYP2C9, CYP2C9*2 and CYP2C9*3, code for enzymes with reduced activity. Despite increasing evidence that patients with these genetic variants require lower maintenance doses of anticoagulant therapy, there is lack of agreement among studies on the risk of bleeding and CYP2C9 polymorphisms. It was, therefore, our objective to study the effect of the CYP2C9 polymorphisms on bleeding complications during initiation and maintenance phases of coumarin anticoagulant therapy. The design of the study was a population-based cohort in a sample of the Rotterdam Study, a study in 7,983 subjects. All patients who started treatment with acenocoumarol or phenprocoumon in the study period from January 1, 1991 through December 31, 1998 and for whom INR data were available were included. Patients were followed until a bleeding complication, the end of their treatment, death or end of the study period. Proportional hazards regression analysis was used to estimate the risk of a bleeding complication in relation to CYP2C9 genotype after adjustment for several potentially confounding factors such as age, gender, target INR level, INR, time between INR measurements, and aspirin use. The effect of variant genotype on bleeding risk was separately examined during the initiation phase of 90 days after starting therapy with coumarins. The 996 patients with analysable data had a mean follow-up time of 481 days (1.3 years); 311 (31.2%) had at least 1 variant CYP2C9 allele and 685 (68.8%) had the wild type genotype. For patients with the wild type genotype, the rate of minor bleeding, major bleeding and fatal bleeding was 15.9, 3.4 and 0.2 per 100 treatment-years, respectively. For patients with a variant genotype, the rate of minor, major and fatal bleeding was 14.6, 5.4 and 0.5 per 100 treatment-years. Patients with a variant genotype on acenocoumarol had a significantly increased risk for a major bleeding event (HR 1.83, 95% CI: 1.01-3.32). During the initiation phase of therapy we found no effect of variant genotype on bleeding risk. In this study among outpatients of an anticoagulation clinic using acenocoumarol or phenprocoumon, having a variant allele of CYP2C9 was associated with an increased risk of major bleeding events in patients on acenocoumarol, but not in patients on phenprocoumon. Although one might consider the assessment of the CYP2C9 genotype of a patient for dose adjustment before starting treatment with acenocoumarol, a prospective randomised trial should demonstrate whether this reduces the increased risk of major bleeding events.

Acenocoumarol↗

Human dopamine transporter gene: coding region conservation among normal, Tourette's disorder, alcohol dependence and attention-deficit hyperactivity disorder populations.

The dopamine transporter (DAT) provides major regulation of the synaptic levels of dopamine and is a principal target of psychostimulant drugs. Associations between DAT gene polymorphisms and human disorders with possible links to dopaminergic neurotransmission, including attention-deficit/hyperactivity disorder (ADHD) and consequences of cocaine and alcohol administration, have been reported. We now report approximately 60000 bp of genomic sequence containing the entire DAT gene. This sequence was used to amplify each of the 15 DAT gene exons and several introns and analyze these amplification products by single-stranded sequence conformation (SSCP) and/or direct sequencing. These results define silent allelic single nucleotide sequence variants in DAT gene exons 2, 6, 9 and 15. Rare conservative mutations are identified in amino acids encoded by DAT exons 2 and 8. Analyses of the common nucleotide variants and the previously reported VNTR in the non-coding region of exon 15 define the pattern of linkage disequilibrium across the DAT locus. These comprehensive analyses, however, fail to identify any common protein coding DAT sequence variant in more than 150 unrelated individuals free of neuropsychiatric disease, 109 individuals meeting City of Hope criteria for Tourette's syndrome, 64 individuals with DSM-IV diagnoses of ethanol dependence, or 15 individuals with ADHD. These data are consistent with substantial evolutionary conservation of the DAT protein sequence. They suggest that gene variants that alter levels of DAT expression provide the best current candidate mechanism for reported associations between DAT gene markers, ADHD and other more tentatively associated neuropsychiatric disorders.

Adolescent↗

Molecular analysis of the presenilin 1 (S182) gene in "sporadic" cases of Alzheimer's disease: identification and characterisation of unusual splice variants.

Mutations of the presenilin 1 (PS-1) gene at the Alzheimer's disease (AD) FAD3 locus on chromosome 14q24.3 are responsible for the majority of familial early-onset AD. As genes responsible for familial forms of AD are obvious candidates for further investigation in "sporadic" disease, we performed a molecular analysis of PS-1 transcripts extracted from brain tissues of a series of histologically confirmed cases of "sporadic" AD (n=10) and also from histologically "normal" (non-Alzheimer) age-matched brain controls (n=5). No sequence changes in the PS-1 coding sequence were detected after analysis by reverse transcription-PCR. This suggests that the frequency of mutations in the PS-1 (S182) coding region in "sporadic" Alzheimer's disease in very low. However, we demonstrated that the PS-1 gene is highly variably spliced. One splice variant involves the 5' untranslated region of the PS-1 gene only and hence encodes for normal PS-1. Six further splice variants involve coding regions of the PS-1 gene and result in truncated proteins lacking specific transmembrane domains. Most of these variants do not coincide with recognized sites of introns in the PS-1 gene. One of these variants, resulting in the loss of transmembrane domain TM-VII, was found only in an AD patient.

Alternative Splicing↗

Genetic characterization of a mumps virus isolate during passaging in the amniotic cavity of embryonated chicken eggs.

The aim of this study was the molecular characterization of a historical mumps isolate (an alleged individual sample). After RNA extraction and cDNA synthesis, selective nested PCR amplification with specific primers, automated DNA sequencing and RFLP analyses were performed. The relative ratios of the detected virus sequences were determined by GeneScan electrophoresis. Phylogenetic tree based on the 316 nucleotide region of the SH gene of the mumps virus was generated by the neighbor-joining method. Results obtained by the described molecular approach show: (a) there are two mumps virus variants, A and B, detected in the fourth passage of wild type virus in the amniotic cavity of embryonated chicken eggs (ECE); (b) variants A and B belong to different genotypes; (c) variants A and B differ in the HN and NP genes which code for amino acid sequences comprising immunogenic epitopes; (d) variant B contains one or more minor variants. We discuss whether the observed differences between the two variants are a consequence of natural heterogeneity or of laboratory contamination in the early passages.

Amino Acid Sequence↗

Novel OXA-10-derived extended-spectrum beta-lactamases selected in vivo or in vitro.

A clinical isolate of Pseudomonas aeruginosa, PAe191, was found to be highly resistant to all anti-Pseudomonas beta-lactam antibiotics (except imipenem) and resistant also to aminoglycosides. It produced a beta-lactamase (with an apparent pI of 7.6) which was not inhibited by clavulanic acid. Cloning and characterization of the beta-lactamase gene showed that it coded for a novel extended-spectrum OXA-10 variant, called OXA-19, which differed from OXA-10 by nine amino acids and from OXA-13 by two, i.e., Asn in position 73 (Asn73) instead of Ser and Asp157 instead of Gly. Asparagine in position 157 is implicated in resistance to ceftazidime, while the amino acid in position 73, in this variant, seems to condition the level of resistance to penicillins. The oxa19 gene was found to be inserted, in a typical integron structure, immediately downstream from an aac(6')-Ib gene coding for an aminoglycoside acetyltransferase variant, which was called AAC(6')-Ib9.

Amino Acid Sequence↗

Screening of the 3' two-thirds of the coding area of the apo B gene in Finnish hypercholesterolemic patients report of six new genetic variants.

Hypercholesterolemia clustering in families not explained by either low density lipoprotein (LDL)-receptor mutations producing familial hypercholesterolemia (FH), or the apolipoprotein B (apo B) Arg3500-->Gln mutation with familial defective apo B (FDB), is common in the Finnish population. In search of previously unknown apo B mutations, we screened exons 26 to 29 of the apo B gene in 68 Finnish severely hypercholesterolemic (> or = 8 mmol/l) non-FH, non-FDB patients, using a single-strand conformation polymorphism analysis based screening method. Four rare and two polymorphic previously unreported DNA variations were detected. The rare variants were a three-nucleotide deletion, with the deletion of Asp2186, an A11961-->G change leading to a Thr3918-->Ala change, a T12922-->G change causing a Val4238-->Ala substitution, and a neutral T12935-->C change leading to a new RsaI cutting site. The polymorphic G12937-->C and G13569-->A changes leading to Arg4243-->Thr and Ala4454-->Thr substitutions, respectively, had minor allele frequencies of 0.03 and 0.02. None of these variants seemed to explain the hyperlipidemia in these patients. A major Finnish mutation causing severe hypercholesterolemia is unlikely to exist in the 3' two-thirds of the coding area of the apo B gene.

Apolipoproteins B↗

Genes and spacers of cloned sea urchin histone DNA analyzed by sequencing.

A cloned histone gene cluster of the highly reiterated type from the sea urchin Psammechinus miliaris was analyzed by DNA sequencing. More than half of the 6 kb repeat was sequenced, including coding regions of all five histones, some prelude and trailing sequences lying adjacent to the structural gense, and segments of the AT-rich spacer DNA. The gene cluster does not code for gonad-specific histone variants but may instead be active in early sea urchin development, as indicated by comparison to reference histones. The encoded histones seem not to be derived from longer precursor proteins, not is there any evidence for insert sequences within the coding regions. Sequence similarities exist among the putative ribosome-binding sites adjacent to the initiator codons of individual genes. The AT-rich spacer segments between the genes differ from each other, are made up from relatively simple nucleotide arrangements, but are not repetitious, and apparently do not code for additional large proteins.

Animals↗

Prediction of distant metastasis by using reverse transcriptase-polymerase chain reaction for epithelial and variant CD44 mRNA in the peripheral blood of patients with colorectal cancer.

BACKGROUND: Reverse transcriptase-polymerase chain reaction (RT-PCR) has been used to identify small numbers of tumor cells. Molecular detection is thought to provide useful information for the clinical management of postoperative adjuvant therapy regimens. OBJECTIVE: To use RT-PCR to identify messenger RNA (mRNA) coding for carcinoembryonic antigen, epithelial and variant CD44, and matrix metalloproteinase 7 in the portal venous and peripheral blood of patients with colorectal carcinoma to predict live or distant metastasis. DESIGN: Prospective consecutive series. SETTING: University hospital. PATIENTS AND METHODS: Portal venous and peripheral blood samples were obtained from 22 patients with colorectal cancer during surgical manipulation. Using complementary DNA primers specific for carcinoembryonic antigen, CD44, and matrix metalloproteinase 7, RT-PCR was performed to detect tumor cells. MAIN OUTCOME MEASURE: The clinical significance of RT-PCR for epithelial and variant CD44 mRNA in peripheral blood. RESULTS: During 3 years of follow-up, 2 patients whose peripheral blood had carcinoembryonic antigen and CD44 variant mRNA also had distant metastases (lung or spleen). Expression of epithelial and variant CD44 mRNA in peripheral blood was more highly correlated with the clinical cancer stage than with expression of carcinoembryonic antigen and matrix metalloproteinase 7. CONCLUSIONS: Molecular detection of epithelial and variant CD44 mRNA in the peripheral blood may help determine distant metastases in patients with colorectal carcinoma. Molecular detection in the peripheral blood at surgical treatment suggests that systemic hematogenic tumor cell dissemination is an early event of distant metastasis.

Carcinoembryonic Antigen↗

SJL/J resistance to mouse hepatitis virus-JHM-induced neurologic disease can be partially overcome by viral variants of S and host immunosuppression.

The basis of the resistance of SJL/J mice to various strains of mouse hepatitis virus (MHV) has been the subject of some debate, especially as it relates to the number and nature of the determinants involved. Our previous work demonstrated that resistance by primary SJL/J glial cultures may involve events subsequent to viral gene expression, possibly due to a defect in cell-to-cell spread of the infection. Since S, the virion's major spike glycoprotein, is known to facilitate the spread of infection due to its syncytiogenic properties, we decided to investigate the role of this viral structural protein in resistance by primary SJL/J glial cells. Variants possessing deletions within the S coding region were able to grow in SJL/J glial cells 10-100 times easier and fuse five-times more efficiently than wt virus. Induction of neurologic disease in SJL/J mice following intracranial inoculation with either wt JHMV or the S deletion variant, AT11f cord, was age-dependent, occurring only in animals inoculated under 4 weeks of age. Resistance in older animals to wt and variant viruses could be abrogated by immunosuppression with cyclosporin A. However, both disease incidence and viral brain titers were higher in animals receiving the JHM variant AT11f cord virus, suggesting that SJL/J resistance to neurologic disease may manifest itself through interactions between inefficient cell-to-cell spread of the infection and protective aspects of the immune response.

Animals↗

Screening for mutations in the steroidogenic acute regulatory protein and steroidogenic factor-1 genes, and in CYP11A and dosage-sensitive sex reversal-adrenal hypoplasia gene on the X chromosome, gene-1 (DAX-1), in hyperandrogenic hirsute women.

Abstract Abnormalities in adrenal and/or ovarian steroidogenesis are found in most patients with hirsutism. The rate-limiting step in the synthesis of steroids in the ovary and the adrenal is the conversion of cholesterol into pregnenolone by cholesterol side-chain cleavage enzyme (P450scc), encoded by the gene CYP11A, after cholesterol is introduced into the mitochondria by the steroidogenic acute regulatory protein (StAR). DAX-1 is a repressor of StAR gene expression, and steroidogenic factor-1 (SF-1) is a regulator of CYP11A, DAX-1, and StAR gene. Mutations in any of these factors resulting in gain of function, or loss of repression, of StAR or P450scc might contribute to the steroidogenic abnormalities present in hirsute patients. In the present study we have screened, using heteroduplex analysis, the genes encoding StAR and SF-1 as well as DAX-1 and CYP11A for mutations in genomic DNA from 19 women presenting with hirsutism and increased serum androgen levels. When variants were found, analysis was extended to a larger group of hyperandrogenic patients and nonaffected women. Two variants were identified in the SF-1 gene. A G-->C change in exon 6, resulting in an Arg(365)Pro mutation, was found in 1 of 45 patients, but not in controls. Also, a Gly(146)Ala missense mutation, resulting from a G-->C change in exon 4, was found in 2 of 48 patients and in 2 of 50 nonaffected individuals. We identified a C-->T base pair change at position -33 of the StAR gene. Three of 48 patients and 3 of 43 controls presented this variant. No mutations were found in coding regions of the StAR gene. Analysis of CYP11A-coding regions identified a G-->A change in exon 3, resulting in a Val(179)Ile missense mutation. This mutation was found in 1 of 29 patients studied and was not present in 50 controls. Finally, analysis of DAX-1 showed no variant in any of the women studied. In conclusion, mutations in StAR, SF-1, CYP11A, and DAX-1 are seldom found in hirsute patients and do not explain the steroidogenic abnormalities found in these women.

Adrenal Glands↗

Cloning and sequencing of a complementary deoxyribonucleic acid coding for a bovine alpha s1-casein A from mammary tissue of a homozygous B variant cow.

A cDNA clone for bovine alpha s1-casein variant A was isolated from a mammary gland cDNA library using a synthetic degenerate oligonucleotide probe. The largest Pst I insert containing an EcoR I site was sequenced. It contained 1090 base pairs, 47 in the 5' noncoding region, 603 in the coding region and 440 in the 3' noncoding region. The nucleotide sequence was compared with three published cDNA sequences for alpha s1-casein variant B. The most obvious difference was the absence of the 39 bases encoding the 13 amino acids that are present in the B variant but absent from the A variant. In addition, five other single base positions differed within individual codons among the four sequences at the third base for each codon, but this did not change the amino acids encoded. There were, however, a number of differences found in the 3' noncoding region. The isolated cDNA was subjected to site-directed mutagenesis to replace a Val-Ile dipeptide with Phe-Phe to increase the chymosin sensitivity of the protein. When the milk proteins from mammary gland tissue extracts were typed, the alpha s1-casein A gene product was not detected.

Amino Acid Sequence↗

Nonallelic histone gene clusters of individual sea urchins (Lytechinus pictus): mapping of homologies in coding and spacer DNA.

The linear arrangement and lengths of the spacers and coding regions in the two nonallelic histone gene variant clusters of L. pictus are remarkably homologous by R loop analysis and are similar in general topography to the histone gene repeat units of other sea urchins examined to date. No interventing sequences were detected. The coding regions of these two histone gene variants share considerable sequence homology; however, there are areas of nonhomology in every spacer region and the lengths of the nonhomologous spacers between the H2A and H1 genes are not the same for the two repeat unit classes (inter-gene heterogeneity). Combining length measurements obtained with both R loops and heteroduplexes suggests that the DNA sequences of the analogous leader regions for the two H1 mRNAs are nonhomologous. Similar observations were made for the H4 leader sequences, as well as the trailer region on H2B. S. purpuratus spacer DNA segments share little sequence homology with L. pictus; however, the analgous coding (and possibly flanking) regions have conserved their sequences. The various coding and spacer regions within a repeat unit do not share DNA sequences. Thus certain areas in the sea urchin histone gene repeat units have been highly conserved during evolution, while other areas have been allowed to undergo considerable sequence change not only between species but within a species.

Animals↗

Prediction of deleterious human alleles.

Single nucleotide polymorphisms (SNPs) constitute the bulk of human genetic variation, occurring with an average density of approximately 1/1000 nucleotides of a genotype. SNPs are either neutral allelic variants or are under selection of various strengths, and the impact of SNPs on fitness remains unknown. Identification of SNPs affecting human phenotype, especially leading to risks of complex disorders, is one of the key problems of medical genetics. SNPs in protein-coding regions that cause amino acid variants (non-synonymous cSNPs) are most likely to affect phenotypes. We have developed a straightforward and reliable method based on physical and comparative considerations that estimates the impact of an amino acid replacement on the three-dimensional structure and function of the protein. We estimate that approximately 20% of common human non-synonymous SNPs damage the protein. The average minor allele frequency of such SNPs in our data set was two times lower than that of benign non-synonymous SNPs. The average human genotype carries approximately 10(3) damaging non-synonymous SNPs that together cause a substantial reduction in fitness.

Alleles↗

Cloning of bovine pyruvate carboxylase and 5' untranslated region variants.

Bovine pyruvate carboxylase (PC; EC 6.4.1.1) cDNA was cloned by reverse transcription (RT) PCR. The coding region plus 3' untranslated region (UTR) of PC mRNA is 3926 bases and encodes 1178 amino acid PC precursor protein. A 5' rapid amplification of cDNA ends protocol was used to clone the 5' end of the mRNA. Six 5'UTR variants ranging from 68 to 363 bp were cloned. Bovine PC 5'UTR (bPC5') variants contain 68 (bPC5'A), 263 (bPC5'B), 363 (bPC5'C), 89 (bPC5'D), 275 (bPC5'E), and 178 bp (bPC5'F). All variants contain a common coding sequence. An RNase protection assay and RT-PCR analysis confirms the presence of the 5'UTR variants. The abundance of PC mRNA, determined by Northern blot analysis, indicates that PC is more abundant in gluconeogenic and lipogenic tissues where all PC variants are expressed compared with tissues that do not possess the full spectrum of PC transcripts. The data suggest that bPC5'A, bPC5'B, and bPC5'F are more abundant in bovine liver than the other variants.

5' Untranslated Regions↗

Variation in the human TAS1R taste receptor genes.

We have performed a comprehensive evaluation of single-nucleotide polymorphisms (SNPs) and haplotypes in the human TAS1R gene family, which encodes receptors for sweet and umami tastes. Complete DNA sequences of TAS1R1-, TAS1R2-, and TAS1R3-coding regions, obtained from 88 individuals of African, Asian, European, and Native American origin, revealed substantial coding and noncoding diversity: polymorphisms are common in these genes, and polymorphic sites and SNP frequencies vary widely in human populations. The genes TAS1R1 and TAS1R3, which encode proteins that act as a dimer to form the umami (glutamate) taste receptor, showed less variation than the TAS1R2 gene, which acts as a dimer with TAS1R3 to form the sweet taste receptor. The TAS1R3 gene, which encodes a subunit common to both the sweet and umami receptors, was the most conserved. Evolutionary genetic analysis indicates that these variants have come to their current frequencies under natural selection during population growth and support the view that the coding sequence variants affect receptor function. We propose that human populations likely vary little with respect to umami perception, which is controlled by one major form of the receptor that is optimized for detecting glutamate but may vary much more with respect to sweet perception.

DNA↗

Predicting functional constraints across evolutionary timescales with phylogeny-informed genomic language models.

Genomic language models (gLMs) have emerged as a powerful approach for learning genome-wide functional constraints directly from DNA sequences. However, standard gLMs adapted from natural language processing often require extremely large model sizes and computational resources, yet still fall short of classical evolutionary models in predictive tasks. Here, we introduce GPN-Star (Genomic Pretrained Network with Species Tree and Alignment Representation), a biologically grounded gLM featuring a phylogeny-aware architecture that leverages whole-genome alignments and species trees to model evolutionary relationships explicitly. Trained on alignments spanning vertebrate, mammalian, and primate evolutionary timescales, GPN-Star achieves state-of-the-art performance across a wide range of variant effect prediction tasks in both coding and non-coding regions of the human genome. Analyses across timescales reveal task-dependent advantages of modeling more recent versus deeper evolution. To demonstrate its potential to advance human genetics, we show that GPN-Star substantially outperforms prior methods in prioritizing pathogenic and fine-mapped GWAS variants; yields unprecedented enrichments of complex trait heritability; and improves power in rare variant association testing. Extending beyond humans, we train GPN-Star for five model organisms - Mus musculus, Gallus gallus, Drosophila melanogaster, Caenorhabditis elegans, and Arabidopsis thaliana - demonstrating the robustness and generalizability of the framework. Taken together, these results position GPN-Star as a scalable, powerful, and flexible new tool for genome interpretation, well suited to leverage the growing abundance of comparative genomics data.

Journal Article↗