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Biomedical subjects

C C Liew

Publications and source records attributed to C C Liew.

At least 73 records · Page 4Linked to original sources
PubMed1996

A novel cDNA encoding for a LIM domain protein located at human chromosome 14q32 as a candidate for leukemic translocation.

A full-length cDNA clone encoding a zinc finger protein was isolated and sequenced. This full-length clone consists of 728 bp and has a predicted open reading frame (ORF) encoding 208 amino acids. The ORF of this polypeptide codes for the human cysteine-rich protein 2 (HCRP2) and has an amino acid sequence that is 92.8% identical to its rat homolog (RCRP2). HCRP2 was mapped to chromosome 14q32, which is a hot spot of translocation in tumor development, by fluorescent in situ hybridization (FISH).

Amino Acid Sequence↗
PubMed1996

Assignment of the human GATA4 gene to 8p23.1-->p22 using fluorescence in situ hybridization analysis.

Using fluorescence in situ hybridization, the human GATA4 gene, a member of the zinc-finger protein family recognizing the consensus GATA motif, was mapped to 8p23.1-->p22. This result, in conjunction with gene mapping data on other GATA-DNA binding proteins, suggests that genes encoding GATA-DNA binding proteins are dispersed throughout the genome, rather than clustered within a single locus.

Chromosomes, Human, Pair 8↗
PubMed1996

Factors involved in cardiogenesis and the regulation of cardiac-specific gene expression.

The delineation of the mechanisms that regulate cardiac gene expression is central to our understanding of cardiac growth and development. Much progress has been made toward the identification of factors involved in tissue-restricted gene expression, especially in skeletal muscle cells. However, the mechanisms regulating the expression of cardiac-specific genes remain less well understood. Certain homeodomain proteins have been implicated in commitment to the cardiac phenotype. Among the best characterized are the murine proteins Csx, Nkx-2.5, and Nkx-2.6, related to the protein tinman, which is essential for heart formation in Drosophila. The expression of these genes precedes that of cardiac-specific genes and is therefore believed to play a critical role in the development of the heart. The GATA proteins are a family of zinc finger proteins that are also expressed early in cardiac development and may act separately from, or in concert with, the homeodomain proteins as crucial regulators of heart development. The myosin heavy and light chain genes, the actin genes, the troponin genes, and the atrial natriuretic factor and muscle creatine kinase genes have served as excellent paradigms for the study of cardiac gene expression. Although differences in cis-acting elements and their behavior in binding assays have been observed between different genes, there exist similarities that are noteworthy. In this review, we will discuss the factors involved in the regulation of cardiac-specific gene expression in an attempt to provide a better understanding of the process of cardiogenesis.

Animals↗
PubMed1995

Angiotensin-I converting enzyme genotypes and left ventricular hypertrophy in patients with hypertrophic cardiomyopathy.

BACKGROUND: The variability of the phenotypic expression of left ventricular hypertrophy (LVH) in patients with hypertrophic cardiomyopathy (HCM) indicates a potential role for additional modifying genes. Variants of angiotensin-I converting enzyme (ACE) gene have been implicated in cardiac hypertrophy. To assess whether ACE genotypes influence the phenotypic expression of hypertrophy, we determined the left ventricular mass index (LVMI) and extent of hypertrophy in 183 patients with HCM. METHODS AND RESULTS: LVMI was derived by the area-length method using two-dimensional echocardiograms. Extent of LVH was determined by a point score method (1 to 10 points). DNA was extracted from blood, and ACE genotyping was performed by polymerase chain reaction (PCR) with an established protocol. Amplification of DNA in the region of polymorphism by PCR of alleles I and D showed 490- and 190-bp products, respectively. ACE genotypes DD, ID, and II were present in 60, 90, and 33 patients with HCM, respectively. In genetically independent patients (n = 108), the mean LVMI (g/m2) was 148 +/- 35.3 in those with DD (n = 35) and 134.2 +/- 33.3 in those with ID and II (n = 73) genotypes (P = .046). LVH score was 6.69 +/- 1.71 in patients with DD and 5.55 +/- 2.19 in those with ID and II genotypes (P = .004). Regression analysis showed that ACE genotypes accounted for 3.7% and 6.5% of the variability of LVMI and LVH score (P = .046 and P = .008, respectively). In 26 patients from a single family, LVMI and LVH score were also greater in patients with DD than in those with ID and II genotypes. ACE genotypes accounted for 14.7% and 10.4% of the variability of the LVMI and extent of hypertrophy, respectively. CONCLUSIONS: ACE genotypes influence the phenotypic expression of hypertrophy in HCM.

Adult↗
PubMed1995

Angiotensinogen gene expression is induced by cyclical mechanical stretch in cultured rat cardiomyocytes.

The effect of cyclical mechanical stretch on angiotensinogen gene expression was examined using a neonatal rat cardiocyte culture system. Cultured cardiocytes grown on a flexible membrane base were stretched by vacuum to 20% of maximum elongation, at 60 cycles/min. The angiotensinogen gene was activated 2 to 5 fold after stretch for 3 to 24 hr, as shown by quantitative reverse transcription polymerase chain reaction. The 5'-flanking region of the angiotensinogen promoter was activated after stretch for 24 hr. This gene expression could be completely suppressed by losartan, a specific antagonist of angiotensin II receptor. These results indicate that (1) cyclical mechanical stretching of cardiocytes is a good model for the study of cardiac hypertrophy-related gene expression; (2) cyclical stretch up-regulates expression of the angiotensinogen gene and (3) the increase in promoter activity may contribute to the induction of angiotensinogen mRNA by cyclical stretch.

Angiotensinogen↗
PubMed1995

Regulation of human cardiac myosin heavy chain genes by cyclical mechanical stretch in cultured cardiocytes.

We examined the effect of cyclical mechanical stretch on the regulation of cardiac myosin heavy chain genes using an isolated neonatal rat cardiocyte culture system. Cultured cardiocytes grown on a flexible membrane were deformed by vacuum to 20% of maximum elongation, at 60 cycles/min in a serum-free medium. Cyclical stretch did not cause myocyte damage as assessed by supernatant LDH measurement and trypan blue exclusion test. The levels of myosin heavy chain (MyHC) mRNA increased as early as 1 h after stretch, reaching 12-fold over the control in 24 h, as shown by Northern blot analysis. However, the proximal 5'-flanking regions of the alpha- and beta-MyHC gene which were linked to chloramphenicol acetyltransferase (CAT) reporter gene did not exhibit enhanced CAT activity following cyclical stretch. Deletion of the chimeric constructs to shorten the 5'-flanking regions of the MyHC genes generated by polymerase chain reaction amplification did not enhance the CAT activity under cyclical stretch. This finding suggests that the stretch-response element of the alpha- and beta-MyHC gene promoter is probably not present in the proximal region of either the alpha- or beta-MyHC genes.

Animals↗
PubMed1995

Identification of a GATA motif in the cardiac alpha-myosin heavy-chain-encoding gene and isolation of a human GATA-4 cDNA.

In an attempt to identify the cardiac-specific genes regulated by the transcription factor GATA-4, we have identified a putative GATA-binding site located within the 5' flanking sequence of the human cardiac alpha-myosin heavy-chain-encoding gene. The 23-bp sequence surrounding the core GATA-binding site is conserved across species. The core motif and flanking sequences of this GATA-binding site are almost identical to that of a well-established GATA-binding site located within the 3' enhancer of the human beta-globin gene. Using electrophoretic mobility shift analysis, two distinct nuclear factors were found to bind specifically to this element. We have isolated a full-length cDNA clone for human GATA-4 (hGATA-4) by screening a human heart cDNA library. The hGATA-4 cDNA sequence shows 85% identity with murine GATA-4 in the protein coding region. The deduced amino-acid sequence within the two zinc-finger DNA-binding domains of human GATA-4 is 100% identical with murine GATA-4. Northern blot analysis reveals that this 4.4-kb transcript has higher expression in adult heart than in fetal heart. Our results suggest that GATA-4 may regulate a set of cardiac-specific genes and play a crucial role in cardiogenesis.

Amino Acid Sequence↗
PubMed1995

Concerted evolution of mammalian cardiac myosin heavy chain genes.

We have recently determined the complete nucleotide sequences of the cardiac alpha- and beta-myosin heavy chain (MyHC) genes from both human and Syrian hamster. These genomic sequence data were used to study the molecular evolution of the cardiac MyHC genes. Between the alpha- and beta-MyHC genes, multiple gene conversion events were detected by (1) maximum parsimony tree analyses, (2) synonymous substitution analyses, and (3) detection of pairwise identity of intron sequences. Approximately half of the 40 cardiac MyHC exons have undergone concerted evolution through the process of gene conversion with the other half undergoing divergent evolution. Gene conversion occurred more often in exons encoding the alpha-helical myosin rod domain than in the globular head domain, and an apparent directional bias was also observed, with transfer of genetic material occurring more often from beta to alpha.

Animals↗
PubMed1995

Characterization and structural organization of the cardiac beta-myosin heavy chain gene from Syrian hamster.

In order to perform comparative studies of the cardiac myosin heavy chain (MyHC) genes, we determined the sequence of the Syrian hamster beta-MyHC gene and its 5' flanking region. This 33,960 basepair (bp) sequence contains 12,196 bp of the 5' flanking region as well as 21,731 bp of the complete beta-MyHC gene, with its 3' end overlapping with the alpha-MyHC gene. All the exon/intron boundaries were determined and relative to the human beta-MyHC gene, an extra 5' untranslated exon was identified. The isolation and sequencing of the Syrian hamster beta-MyHC gene may further the understanding about the regulation and the evolution of the cardiac MyHC genes.

Amino Acid Sequence↗
PubMed1994

A catalogue of genes in the cardiovascular system as identified by expressed sequence tags.

The heart, which is composed of all the cellular components of the circulatory system, is a representative organ for obtaining genes expressed in the cardiovascular system in normal and disease states. We used partial sequences of cDNA clones, or expressed sequence tags, to identify and tag genes expressed in this organ. More than 3500 partial sequences representing > 3000 cDNA clones have been obtained from either the 5' or 3' end of inserts derived from human heart cDNA libraries. Of 3132 cDNA clones analyzed by sequence similarity searching against the GenBank/EMBL data bases, 1485 (47.4%) were found to represent additional, previously undiscovered genes, whereas 267 clones were matched to human brain expressed sequence tags. Clones matching to known genes were catalogued according to their putative structural and cellular functions. cDNA probes from reverse-transcribed mRNAs of fetal and adult hearts were used to study differential expression of selected clones in cardiac development. Cataloguing genes expressed in the heart may provide insight into the genes involved in health and cardiovascular disease.

Adult↗
PubMed1994

The human BAT3 ortholog in rodents is predominantly and developmentally expressed in testis.

A partial cDNA clone, RLC34, was isolated from a rat brain cDNA library. Its sequence exhibits high identity with BAT3 (88.4% and 94.9% for DNA and the deduced amino acid sequence, respectively), a gene located within the region of human major histocompatibility complex III (MCHIII region). RLC34 detected a transcript the same size in human and rat, similar to that reported for BAT3. Southern blot analysis of RLC34 showed similar restriction patterns as those of the human BAT3 gene. A panel of rodent tissue samples were examined and the RLC34 was found to be predominantly expressed in the germ cells of rodent testes. The expression is developmentally regulated with increased transcripts seen at 17-20 days after birth. Its testicular expression, its association with spermatogenesis, and its location in MCHIII suggest a correlation of RLC34 with the growth-reproduction complex (grc). This finding may also provide a clue to study the function of other genes localized in this area of the MCHIII region.

Adult↗
PubMed1994

Characterization and nucleotide sequence of the cardiac alpha-myosin heavy chain gene from Syrian hamster.

In small mammals, the cardiac alpha-myosin heavy chain (MyHC) gene is predominantly expressed in the adult ventricle, while the beta-MyHC gene is predominantly expressed in the fetal ventricle. In order to perform comparative studies of these genes, we sequenced the Syrian hamster alpha-MyHC gene by determining a continuous 32,415 base pair (bp) sequence. It contained 39 exons encoding a predicted polypeptide of 1939 amino acid residues (aa) with a molecular weight of 223,644 Da. Sequence comparison revealed that the coding sequence is highly identical to that of the human alpha-MyHC gene. A marked feature of the Syrian hamster alpha-MyHC gene was the abundance of reiterated sequences within introns. Eleven B1 and four B2 retroposons were identified, a variety of di-, tri-, and tetra-nucleotide repeats were present, and three longer direct repeats were found. Some of them appear to be associated with genetic recombination events.

Amino Acid Sequence↗
PubMed1994

Single pass sequencing of a unidirectional human fetal heart cDNA library to discover novel genes of the cardiovascular system.

A human fetal heart cDNA library was constructed in the lambda gt22A expression vector. Polymerase chain reaction (PCR) was used to amplify the cDNA inserts. PCR products were purified and used in cycle sequencing reactions in the presence of a fluorescein-conjugated primer and electrophoresed on a Pharmacia A.L.F. Sequencer. Partial cDNA sequences, or expressed sequence tags (ESTs) were searched against the Genbank and EMBL databases to identify novel genes expressed in the human cardiovascular system.

Base Sequence↗
PubMed1994

The identification of NP25: a novel protein that is differentially expressed by neuronal subpopulations.

A novel gene encoding a 25-kDa neuronal-specific protein, here named 'NP25', has been isolated as a cDNA clone from rat brain. The sequence of the NP25 cDNA reveals a single open reading frame that encodes a primary translation product of 206 amino acids. A search of the protein sequence databank indicates that NP25 is significantly homologous with three recently discovered muscle proteins: SM22 alpha, mp20 and calponin. The gene is specifically and ubiquitously expressed in the rat brain and has conserved sequences among chicken, rat, mouse and human. Rat brain NP25 was identified by Western blot using an antiserum elicited against trpE-NP25 fusion protein. On pH gradient electrophoresis, NP25 was separated into at least two isoforms with similar molecular weights. Immunocytochemistry and in situ hybridization demonstrated that NP25 was differentially expressed by neuronal subpopulations of the rat central nervous system. The highest concentration of NP25 protein was localized in central amygdaloid nuclei and glomeruli in the granule layer of cerebellum. The wide and differential distribution of NP25 in the brain suggests that it may play a particular important role in the function of specific neuronal systems.

Amino Acid Sequence↗
PubMed1993

Serial deletion constructs of human cardiac myosin heavy chain genes generated by PCR amplification.

Serial deletion constructs derived from the 5'-flanking regions of the human cardiac alpha- and beta-myosin heavy chain genes were generated by polymerase chain reaction (PCR) amplifications. Generation of different length chimeric constructs were based on the complete sequence of the human cardiac myosin heavy chain genes. The primers were synthesized with HindIII and BamH1 sites and were linked to any designed nucleotide of the 5' flanking sequence of the myosin heavy chain gene(s). Following the PCR amplification and the site-directed mutagenesis, the PCR products were verified by DNA sequencing and subsequently ligated to the chloramphenicol acetyltransferase (pBLCAT3) reporter gene which was restricted with Hind III and BamH1. Neonatal rat cardiocytes were used to assay the promotor activity (i.e. CAT activity) of different lengths of the chimeric constructs of the gene.

Animals↗
PubMed1993

Characterization of Zn(2+)-binding nuclear proteins present in the myocardium.

Nonhistone nuclear proteins were isolated from 3-5 day old neonatal as well as 3 month-old adult myocardium. The nuclear proteins were separated and analyzed by two-dimensional polyacrylamide gel electrophoresis. Using a blot transfer technique equilibrated with 65Zn2+, at least four polypeptides exhibited Zn(2+)-binding activity over the spectrum of nonhistone nuclear proteins. A protein with a molecular weight of 68kDa pI7.8, which has been characterized for its involvement in nucleosome structure, consistently binds Zn2+ in both the neonatal and adult myocardium. This nuclear protein has now been further characterized by partial amino acid microsequencing. It was found that this novel polypeptide is distinct from the pore-complex lamina proteins. Three other polypeptides with M tau 90kDa, pI7.8, M tau 68kDa, pI6.5 and M tau 35kDa, pI7.5 exhibited increased Zn(2+)-binding activity in neonatal myocardium as compared to adult myocardium. Together with results from our previous studies, this study provides the first evidence implicating Zn(++)-binding nuclear proteins in the processes of growth and differentiation of myocardial development.

Amino Acid Sequence↗