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M Emi

Publications and source records attributed to M Emi.

At least 199 records · Page 11Linked to original sources
PubMed1993

A novel metalloprotease/disintegrin-like gene at 17q21.3 is somatically rearranged in two primary breast cancers.

From chromosomal region 17q21.3, where a tumour suppressor gene(s) for breast and ovarian cancers is thought to be present, we have isolated a novel gene from a cosmid clone that revealed somatic rearrangements in two breast cancers. The gene (MDC) encodes a 524-amino acid metalloprotease-like, disintegrin-like and cysteine-rich protein with sequence similarity to members of the snake-venom metalloprotease/disintegrin family and guinea-pig sperm-surface protein PH-30. These proteins have been implicated in cell-cell or cell-extracellular matrix interactions. Rearrangements in both tumours involve multiple exons and disrupt the coding region of the new MDC.

Amino Acid Sequence↗
PubMed1993

Detailed analysis of genetic alterations in colorectal tumors from patients with and without familial adenomatous polyposis (FAP).

To examine early genetic events during colorectal carcinogenesis, we searched for genetic alterations in 75 adenomas from seven patients with familial polyposis coli (FAP) and in 64 sporadic colorectal tumors (63 carcinomas and one adenoma). We investigated germ-line and somatic mutations in the APC gene, somatic mutations in the K-ras and p53 genes, and loss of heterozygosity (LOH) on chromosome 8p21-22. Thirty-two FAP adenomas carried detectable somatic mutations in the APC gene. The frequency of somatic APC mutations among adenomas was the same regardless of differences in size or histopathological classification. On the other hand, K-ras mutation was very rare in small adenomas where dysplasia was mild or moderate but frequent in large adenomas with severe dysplasia. Mutation of the p53 gene was observed in only two adenomas and LOH on 8p22 was detected in none. These results imply that a second 'hit' in the APC gene, but not necessarily mutation in K-ras or p53, is an important and critical event for formation of a colorectal adenoma.

Adenomatous Polyposis Coli↗
PubMed1992

Missense mutations in exon 5 of the human lipoprotein lipase gene. Inactivation correlates with loss of dimerization.

Most missense mutations of the lipoprotein lipase (LPL) gene identified among LPL-deficient subjects cluster in a segment of the sequence that encodes the catalytic triad as well as functional elements involved in the activation of the lipase at lipid-water interfaces. Consequently, loss of activity may result either from direct alterations of such functional elements or from less specific effects on protein folding and stability. This issue was addressed by examining biochemical properties of four such variants (A176T, G188E, G195E, and S244T) in a heterologous expression system (COS-1 cells). Variant G195E (GGA----GAA) was previously unreported. In all instances, inactive enzyme was recovered in medium, albeit at reduced levels. Cellular synthesis and extracellular degradation were similar to those for wild type, suggesting that reduced secretion resulted from increased intracellular degradation. When cell extracts were subjected to heparin-Superose affinity chromatography followed by elution on a linear salt gradient, all variants exhibited a single, inactive, low affinity immunoreactive peak. By contrast, wild-type enzyme presented an additional, high affinity, active species, which we interpret as homodimeric enzyme. Substitution of the active-site serine (S132A) led to loss of activity but maintenance of the high affinity species. When large amounts of the G188E variant were applied to the column, small but significant amounts of high affinity, active enzyme were recovered. Systematic substitutions at residue 188 showed that only glycine could accommodate structural constraints at this position. We conclude that the mutations examined did not impart lipase deficiency by affecting specific functional elements of the enzyme. Rather, they appear to affect protein folding and stability, and thereby formation and maintenance of subunit assembly.

Adult↗
PubMed1992

Frequent loss of heterozygosity for loci on chromosome 8p in hepatocellular carcinoma, colorectal cancer, and lung cancer.

Frequent loss of heterozygosity at chromosomal loci in a specific tumor type may indicate the presence of a tumor suppressor gene. We have examined loss of heterozygosity on chromosome 8p in paired tumor and constitutional DNA from 346 patients representing seven different types of human cancer. Frequent allelic losses were observed in hepatocellular carcinoma (22 of 46 cases, 47.8%), in colorectal cancer (12 of 26, 46.2%), and in non-small cell lung cancer (14 of 35, 40.0%), in contrast to low frequencies detected in breast cancer (5 of 56, 8.9%) and renal cell carcinoma (2 of 27, 7.4%). Ovarian cancer and gastric cancer showed intermediate frequencies of 33.3% and 22.2%. Subsequent analysis of 120 hepatocellular carcinomas and 94 colorectal cancers with five polymorphic markers along the short arm of chromosome 8 defined commonly deleted regions within the same chromosomal interval, 8p23. 1-8p21.3, suggesting that one or more tumor suppressor genes for both cancers may be present in that region.

Alleles↗
PubMed1992

Isolation and mapping of 88 new RFLP markers on human chromosome 8.

To obtain new RFLP markers for construction of a high-resolution map of human chromosome 8, a cosmid library was constructed from a somatic hybrid cell that contained chromosome 8 as the only human component in mouse genomic background. Eighty-eight new RFLP markers were isolated and characterized, and 71 of them were sublocalized to chromosomal bands by fluorescent in situ hybridization (FISH). Of these, 36 were localized to the short arm, 34 to the long arm, and 1 to the centromeric region. Five markers defined VNTR loci. This work represents the first extensive isolation and physical mapping of RFLP markers on human chromosome 8. These new markers will serve as useful resources for linkage mapping of loci for inherited diseases and for efforts to identify a putative tumor suppressor gene(s) on chromosome 8.

Autoradiography↗
PubMed1992

cDNA cloning and expression of rat tissue factor pathway inhibitor (TFPI).

Tissue factor pathway inhibitor (TFPI) is a factor Xa-dependent inhibitor for the factor VIIa-tissue factor complex. We isolated cDNA for rat TFPI by screening a lambda gt10 rat liver cDNA library. We determined the 1,228 bp nucleotide sequence, comprising a 88 bp 5' non-coding region, a 906 bp open reading frame, and a 234 bp 3' non-coding region, which encodes a protein of 302 amino acid residues. On Northern blot analysis of rat TFPI mRNA, rat TFPI mRNA was detected as two forms with different molecular sizes, 4.0 and 1.4 kb, which were expressed abundantly in heart, lung, kidney, and aortic endothelial cells. The homology of the amino acid sequence of rat TFPI with those of human and rabbit TFPI was found to be 60.7 and 57.4%, respectively. The lengths of the three tandem Kunitz-type inhibitor domains were strictly conserved not only among TFPI from the three species, but also among other proteins containing Kunitz-type inhibitor domains. The homology of the Kunitz-type domains in TFPI among the three species was 57, 86, and 69% in the 1st, 2nd, and 3rd domains, respectively. There was no significant difference in hydropathy profiles of TFPI from man, rabbit, and rat.

Amino Acid Sequence↗
PubMed1991

The effect of genetic determinants of low density lipoprotein levels on lipoprotein (a).

Levels of Lipoprotein(a) [Lp(a)] correlate directly with atherosclerosis risk. The Lp(a) particle is physically and chemically similar to low density lipoprotein (LDL), the main difference being the presence of apolipoprotein(a) [apo(a)] bonded to the apoB-100 moiety of LDL. Genetic variation of apo(a) primarily determines Lp(a) phenotype. However, other genetic factors may also have a role in determining Lp(a) levels. Large families provide a unique opportunity to evaluate the contribution of genetic factors to disease. In several large Utah kindreds with various genetic abnormalities of lipoprotein metabolism we determined that: 1) Lp(a) levels are associated with defects at the apoB gene; 2) Lp(a) levels are not associated with defects at the LDL-receptor gene; 3) high density lipoprotein (HDL) levels are associated with genetic variation at the apo(a) locus; and 4) the DNA sequence of the apoB-100 binding domain does not vary between siblings with high and low Lp(a) levels.

Apolipoprotein B-100↗
PubMed1990

Direct detection and automated sequencing of individual alleles after electrophoretic strand separation: identification of a common nonsense mutation in exon 9 of the human lipoprotein lipase gene.

Large-scale screening by direct sequencing of DNA to detect molecular variants remains a laborious endeavor whose difficulty is compounded by heterozygosity. We show that mobility shifts of single-stranded DNA electrophoresed under nondenaturing conditions can be used not only to detect variants (Orita,M. et al., 1989, Genomics, 5, 874-879), but also to separate and sequence directly individual alleles. In this manner, we have identified a common variant of human lipoprotein lipase resulting from a nonsense mutation in exon 9 of the gene. Whether this variant is of functional significance remains to be determined.

Alleles↗
PubMed1990

Cloning and characterization of a third type of human alpha-amylase gene, AMY2B.

We have previously reported concerning the existence of a third type of human alpha-amylase gene, AMY3 [Emi et al., Gene 62 (1988) 229-235; Tomita et al., Gene 76 (1989) 11-18], which is expressed in a lung carcinoid tissue, and differs in nucleotide sequence from the two previously characterized human alpha-amylase genes coding for salivary and pancreatic isozymes, termed AMY1 and AMY2, respectively. Here, we rename this gene AMY2B to coincide with the designation by Gumucio et al. [Mol. Cell Biol. 8 (1988) 1197-1205] and describe its genetic properties as revealed by sequencing studies. It consists of ten major exons whose sequences are highly homologous to those of AMY1 and AMY2. Not only the exons, but also most of the introns seem to be highly conserved, as judged from physical mapping data. The AMY2B gene identified from mRNA in a lung carcinoid tissue has at least two additional untranslated exons in its 5' region; hence the promoter lies far upstream relative to the other two AMY genes.

Base Sequence↗
PubMed1990

Alveolar epithelial cell plasminogen activator. Characterization and regulation.

Intra-alveolar fibrin deposition is one of the pathological hallmarks of acute lung injury. Because alveolar epithelial cells play a central role in the repair process following acute lung injury, this study was undertaken to examine their potential to produce a plasminogen activator (PA). We now report the synthesis and secretion of PA by rat alveolar epithelial cells with the catalytic properties of a urokinase-type (u-PA) rather than tissue-type plasminogen activator. Studies of regulation of epithelial cell u-PA revealed: 1) phorbol myristate acetate (PMA) but not the inactive structural analog 4 alpha-PMA upregulated u-PA synthesis, putatively via the protein kinase C pathway; 2) PMA induction of u-PA activity was substantially inhibited by dexamethasone and completely inhibited by cycloheximide; 3) unstimulated alveolar epithelial cells had no detectable u-PA mRNA, whereas PMA exposure led to activation of the u-PA gene and accumulation of a 2.5-kilobase u-PA mRNA; and 4) cycloheximide did not abolish this induction of u-PA mRNA suggesting that intermediate protein synthesis was not necessary for the activation of transcription. In light of their capacity to promote fibrinolysis and their strategic anatomic location, alveolar epithelial cells are likely to play a key role in the extensive remodelling process that follows acute lung injury.

Amiloride↗
PubMed1990

Missense mutation (Gly----Glu188) of human lipoprotein lipase imparting functional deficiency.

Cloning and sequencing of lipoprotein lipase (LPL) cDNA prepared from the adipose tissue of a patient with classical LPL deficiency revealed a G to A transition at nucleotide 818 in all sequenced clones, leading to the substitution of glutamic acid for glycine at residue 188 of the mature protein. Hybridization of genomic DNA with allele-specific oligonucleotides confirmed that the patient was homozygous for this mutation and revealed that carrier status for this mutation among relatives of the patient was significantly associated with hypertriglyceridemia. Assay of the patient's plasma for immunoreactive enzyme and activity demonstrated the presence of a circulating inactive enzyme protein, the concentration of which was further increased by injection of heparin. The mutant sequence was produced by oligonucleotide-directed mutagenesis, and both normal and mutant sequences were cloned into the expression vector pSVL and transfected into COS-1 cells. The normal sequence led to the in vitro expression of an enzyme that bound to heparin-Sepharose and had a specific catalytic activity similar to that of normal postheparin plasma enzyme. By contrast, the mutant enzyme expressed in vitro was catalytically inactive and displayed a lower affinity for heparin than the normal enzyme. We conclude that this single amino acid substitution leads to the in vivo expression of an inactive enzyme accounting for the manifestations of LPL deficiency noted in the patient.

Adipose Tissue↗
PubMed1990

Phenotypic expression of heterozygous lipoprotein lipase deficiency in the extended pedigree of a proband homozygous for a missense mutation.

Familial lipoprotein lipase (LPL) deficiency is a rare genetic disorder accompanied by well-characterized manifestations. The phenotypic expression of heterozygous LPL deficiency has not been so clearly defined. We studied the pedigree of a proband known to be homozygous for a mutation resulting in nonfunctional LPL. Hybridization of DNA from 126 members with allele-specific probes detected 29 carriers of the mutant allele. Adipose tissue LPL activity, measured previously, was reduced by 50% in carriers, but did not reliably distinguish them from noncarriers. Carriers were prone to the expression of a form of familial hypertriglyceridemia characterized by increased plasma triglyceride, VLDL cholesterol and apolipoprotein B, and decreased LDL and HDL cholesterol concentrations. These manifestations were age modulated, with conspicuous differences between carriers and noncarriers observed only after age 40. Several noncarriers exhibited similar lipid abnormalities, but without the inverse relationship between VLDL cholesterol and LDL cholesterol noted among carriers. In addition to age and carrier status, the potentially reversible conditions, obesity, hyperinsulinemia and lipid-raising drug use were contributory. Thus heterozygous lipoprotein lipase deficiency, together with age-related influences, may account for a form of familial hypertriglyceridemia.

Adipose Tissue↗
PubMed1990

Compound heterozygote for lipoprotein lipase deficiency: Ser----Thr244 and transition in 3' splice site of intron 2 (AG----AA) in the lipoprotein lipase gene.

Cloning and sequencing of translated exons and intron-exon boundaries of the lipoprotein lipase gene in a patient of French descent who has the chylomicronemia syndrome revealed that he was a compound heterozygote for two nucleotide substitutions. One (TCC----ACC) leads to an amino acid substitution (Ser----Thr244), while the other alters the 3' splice site of intron 2 (AG----AA). The functional significance of the Thr244 amino acid substitution was established by in vitro expression in cultured mammalian cells.

Amino Acid Sequence↗
PubMed1990

Lipoprotein lipase deficiency resulting from a nonsense mutation in exon 3 of the lipoprotein lipase gene.

In DNA from a male patient of German and Polish ancestry who has lipoprotein lipase deficiency, sequencing of all nine exons and intron-exon boundaries corresponding to the coding region of the lipoprotein lipase gene detected a C----T transition leading to the substitution of a stop signal for the codon that normally determines a glutamine at position 106 of the mature enzyme. Hybridization with allele-specific oligonucleotides at this position established that the patient was homozygous for this mutation. This mutation must lead to the synthesis of a sharply truncated protein, accounting for the enzymatic deficiency noted in the patient.

Base Sequence↗