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Biomedical subjects

E Chung

Publications and source records attributed to E Chung.

At least 19 recordsLinked to original sources
PubMed2004

Expression and function of peroxisome proliferator-activated receptors in human melanocytes.

BACKGROUND: Peroxisome proliferator-activated receptors (PPARs) belong to the superfamily of nuclear receptors that heterodimerize with the retinoic X receptor. Agonists of PPAR have been known to play an important role in cellular responses including proliferation and differentiation. The expression and function of PPARs have not been investigated in human melanocytes, although they have been widely demonstrated in keratinocytes of the skin. OBJECTIVES: To investigate the expression of PPARs in human melanocytes and the effects of PPAR activators on melanocyte growth and melanogenesis. METHODS: We used immunocytochemistry and Western blot analysis to determine whether PPARs are expressed in melanocytes. To investigate further expression of PPAR subtypes, reverse transcriptase-polymerase chain reaction analysis was performed using PPAR subtype-specific oligonucleotides. The cell proliferation was measured using the Coulter counter. The effects on pigmentation were investigated with measurement of melanin contents, tyrosinase activity and its expression. RESULTS: The mRNA of all three PPAR subtypes, PPAR-alpha, PPAR-beta/delta and PPAR-gamma, were expressed in melanocytes. Activators for PPAR-alpha (WY-14643) and PPAR-gamma (ciglitazone) inhibited proliferation of melanocytes in a dose-dependent manner, whereas bezafibrate, a preferential activator for PPAR-beta/delta, had no effect. This growth inhibition was accompanied by the morphological change of the melanocytes to an activated form with an increased number of dendrites and enlarged cell area compared with the control. The WY-14643 and ciglitazone also appeared to stimulate the melanin synthesis of melanocytes. This increase in pigmentation was due to stimulation of the tyrosinase activity without an increase in the expression of tyrosinase. CONCLUSIONS: PPARs are expressed in human melanocytes and PPAR-alpha and PPAR-gamma activators inhibit melanocyte growth and stimulate melanogenesis.

Blotting, Western↗
PubMed2001

Cloning of BNIP3h, a member of proapoptotic BNIP3 family genes.

Apoptosis is regulated by interaction of antiapoptotic Bcl-2 family proteins with various proapoptotic proteins, several of which are also members of the Bcl-2 family. BNIP3 (formerly NIP3) is a proapoptotic mitochondrial protein classified in the Bcl-2 family based on limited sequence homology-3 (BH3) domain and COOH-terminal transmembrane domain. Sequence comparison of BNIP3 has indicated that there are several BNIP3 human homologs of this protein, like BNIP3L, Nix and BNIP3. We have cloned a new member of BNIP3 family from the cDNA library prepared from human dermal papilla cells and designated as BNIP3h. BNIP3h shows substantial homology with other BNIP3 family proteins. BNIP3h induced apoptosis from 24 hours after transfection in MCF7 cell lines and its apoptosis inducing activity is extended until 72 hours after transfection.

Amino Acid Sequence↗
PubMed2001

Axonemal beta heavy chain dynein DNAH9: cDNA sequence, genomic structure, and investigation of its role in primary ciliary dyskinesia.

Dyneins are multisubunit protein complexes that couple ATPase activity with conformational changes. They are involved in the cytoplasmatic movement of organelles (cytoplasmic dyneins) and the bending of cilia and flagella (axonemal dyneins). Here we present the first complete cDNA and genomic sequences of a human axonemal dynein beta heavy chain gene, DNAH9, which maps to 17p12. The 14-kb-long cDNA is divided into 69 exons spread over 390 kb. The cDNA sequence of DNAH9 was determined using a combination of methods including 5' rapid amplification of cDNA ends, RT-PCR, and cDNA library screening. RT-PCR using nasal epithelium and testis RNA revealed several alternatively spliced transcripts. The genomic structure was determined using three overlapping BACs sequenced by the Whitehead Institute/MIT Center for Genome Research. The predicted protein, of 4486 amino acids, is highly homologous to sea urchin axonemal beta heavy chain dyneins (67% identity). It consists of an N-terminal stem and a globular C-terminus containing the four P-loops that constitute the motor domain. Lack of proper ciliary and flagellar movement characterizes primary ciliary dyskinesia (PCD), a genetically heterogeneous autosomal recessive disorder with respiratory tract infections, bronchiectasis, male subfertility, and, in 50% of cases, situs inversus (Kartagener syndrome, KS). Dyneins are excellent candidate genes for PCD and KS because in over 50% of cases the ultrastructural defects of cilia are related to the dynein complex. Genotype analysis was performed in 31 PCD families with two or more affected siblings using a highly informative dinucleotide polymorphism located in intron 26 of DNAH9. Two families with concordant inheritance of DNAH9 alleles in affected individuals were observed. A mutation search was performed in these two "candidate families," but only polymorphic variants were found. In the absence of pathogenic mutations, the DNAH9 gene has been excluded as being responsible for autosomal recessive PCD in these families.

Adenosine Triphosphate↗
PubMed2001

Drosophila scavenger receptor CI is a pattern recognition receptor for bacteria.

One hallmark of innate immunity apparently conserved from primitive life forms through to humans is the ability of the host to recognize pathogen-associated molecular patterns (PAMPs). Since macrophage pattern recognition receptors are not well defined in Drosophila, we set out to identify such receptors. Our findings reveal that Drosophila macrophages express multiple pattern recognition receptors and that the Drosophila scavenger receptor, dSR-CI, is one such receptor capable of recognizing both gram-negative and gram-positive bacteria, but not yeast. Our data indicate that scavenger receptor bacterial recognition is conserved from insects to humans and may represent one of the most primitive forms of microbial recognition.

Amino Acid Sequence↗
PubMed2000

A new family of adenylyl cyclase genes in the male germline of Drosophila melanogaster.

We describe the cloning and characterization of a new gene family of adenylyl cyclase related genes in Drosophila. The five adenylyl cyclase-like genes that define this family are clearly distinct from previously known adenylyl cyclases. One member forms a unique locus on chromosome 3 whereas the other four members form a tightly clustered, tandemly repeated array on chromosome 2. The genes on chromosome 2 are transcribed in the male germline in a doublesex dependent manner and are expressed in postmitotic, meiotic, and early differentiating sperm. These genes therefore provide the first evidence for a role for the cAMP signaling pathway in Drosophila spermatogenesis. Expression from this locus is under the control of the always early, cannonball, meiosis arrest, and spermatocyte arrest genes that are required for the G2/M transition of meiosis I during spermatogenesis, implying a mechanism for the coordination of differentiation and proliferation. Evidence is also provided for positive selection at the locus on chromosome 2 which suggests this gene family is actively evolving and may play a novel role in spermatogenesis.

Adenylyl Cyclases↗
PubMed2000

Primary ciliary dyskinesia: a genome-wide linkage analysis reveals extensive locus heterogeneity.

Primary ciliary dyskinesia (PCD), or immotile cilia syndrome (ICS), is an autosomal recessive disorder affecting ciliary movement with an incidence of 1 in 20000-30000. Dysmotility to complete immotility of cilia results in a multisystem disease of variable severity with recurrent respiratory tract infections leading to bronchiectasis and male subfertility. Ultrastructural defects are present in ciliated mucosa and spermatozoa. Situs inversus (SI) is found in about half of the patients (Kartagener syndrome). We have collected samples from 61 European and North American families with PCD. A genome-wide linkage search was performed in 31 multiplex families (169 individuals including 70 affecteds) using 188 evenly spaced (19cM average interval) polymorphic markers. Both parametric (recessive model) and non-parametric (identity by descent allele sharing) linkage analyses were used. No major locus for the majority of the families was identified, although the sample was powerful enough to detect linkage if 40% of the families were linked to one locus. These results strongly suggest extensive locus heterogeneity. Potential genomic regions harbouring PCD loci were localised on chromosomes 3p, 4q, 5p, 7p, 8q, 10p, 11q, 13q, 15q, 16p, 17q and 19q. Linkage analysis using PCD families with a dynein arm deficiency provided 'suggestive' evidence for linkage to chromosomal regions 8q, 16pter, while analyses using only PCD families with situs inversus resulted in 'suggestive' scores for chromosomes 8q, and 19q.

Ciliary Motility Disorders↗
PubMed2000

Digital measurement of torsional eye movement due to postural change and its effect on reading performance.

PURPOSE: Posture induced torsional eye movements have rarely been investigated. The current study made use of digital imaging technology to measure the cycloduction resulting from postural change. The effect of cycloduction on reading performance was also investigated. METHODS: Thirty subjects were recruited and pictures of the right eye were captured using a digital camera at three postures, i.e. sitting, 90 degrees tilted to the right and 90 degrees tilted to the left. With the identification of a conjunctival landmark, torsional eye movement was measured. The subjects were then required to read a custom designed near chart while in those three postures, the reading card being rotated 90 degrees clockwise or 90 degrees anti-clockwise, to match with the tilting of the head. The reproducibility of the torsional eye movement and reading performance measure was determined in 12 of those 30 subjects. RESULTS: Incycloduction was induced when tilting to the right and excycloduction when tilting to the left. This method was found to be reproducible with the 95% confidence limits of 0.80 degrees between visits. The mean incycloduction induced was 6.50 degrees (SD 1.51 degrees ) and 6.41 degrees (SD 1.46 degrees ) for excycloduction. No significant difference in amount was demonstrated (paired t-test: t = 0.624, P = 0.538). No significant difference was found in the reading scores at various postures (Repeated measures ANOVA: df = 2, F = 1.881, P = 0.162). CONCLUSIONS: The results presented here demonstrate that we have developed an objective and instantaneous method with good precision, which could be applied in other studies that require the measurement of torsional eye movements. The induced cycloduction did not affect the reading performance.

Adolescent↗
PubMed2000

Chinese tonal language rehabilitation following cochlear implantation in children.

Cantonese language rehabilitation in 28 prelingually deaf children who underwent cochlear implantation was evaluated. All patients were implanted with multichannel devices and the operations went smoothly. They all had improved scores on audiological assessments and speech perception tests. The speech evaluation tests included the recognition of sounds, vowels, consonants and tone. Sentence recognition and story comprehension were both improved after training for 2 years. Cochlear implantation is a useful measure for the speech rehabilitation of prelingually profound deaf children when hearing aids are of no benefit. The multichannel implant device is of clinical significance in the rehabilitation of those patients using tonal language.

Child↗
PubMed2000

A locus for primary ciliary dyskinesia maps to chromosome 19q.

Primary ciliary dyskinesia is an autosomal recessive condition characterised by chronic sinusitis, bronchiectasis, and subfertility. Situs inversus occurs in 50% of cases (Kartagener syndrome). It has an estimated incidence of 1 in 20 000 live births. The clinical phenotype is caused by defective ciliary function associated with a range of ultrastructural abnormalities including absent dynein arms, absent radial spokes, and disturbed ciliary orientation. The molecular genetic basis is unknown. A genome scan was performed in five Arabic families. Using GENEHUNTER, a maximal multipoint lod score (HLOD) of 4.4 was obtained on chromosome 19q13.3-qter at alpha (proportion of linked families) = 0.7. A 15 cM critical region is defined by recombinations at D19S572 and D19S218. These data provide significant evidence for a PCD locus on chromosome 19q and confirm locus heterogeneity.

Adult↗
PubMed2000

No deleterious mutations in the FOXJ1 (alias HFH-4) gene in patients with primary ciliary dyskinesia (PCD).

The transcription factor FOXJ1 (alias HFH-4 or FKHL13) of the winged-helix/forkhead family is expressed in cells with cilia or flagella, and seems to be involved in the regulation of axonemal structural proteins. The knockout mouse Foxj1(-/-) shows abnormalities of organ situs, consistent with random determination of left-right asymmetry, and a complete absence of cilia. The human FOXJ1 gene which maps to chromosome 17q, is thus an excellent candidate gene for Kartagener Syndrome (KS), a subphenotype of Primary Ciliary Dyskinesia (PCD), characterized by bronchiectasis, chronic sinusitis and situs inversus. We have collected samples from 61 PCD families, in 31 of which there are at least two affected individuals. Two families with complete aciliogenesis, and six families, in which the affected members have microsatellite alleles concordant for a locus on distal chromosome 17q, were screened for mutations in the two exons and intron-exon junctions of the FOXJ1 gene. No sequence abnormalities were observed in the DNAs of the affected individuals of the selected families. These results demonstrate that the FOXJ1 gene is not responsible for the PCD/KS phenotype in the families examined.

Alleles↗
PubMed1999

The transcriptional activation domain of VP16 is required for efficient infection and establishment of latency by HSV-1 in the murine peripheral and central nervous systems.

The herpes simplex virus (HSV) transactivator VP16 is a structural component of the virion that activates immediate-early viral gene expression. The HSV-1 mutant in1814, which contains a 12-bp insertion that compromises the transcriptional function of VP16, replicated to a low level if at all in the trigeminal ganglia of mice (I. Steiner, J. G. Spivack, S. L. Deshmane, C. I. Ace, C. M. Preston, and N. W. Fraser (1990). J. Virol. 64, 1630-1638; Valyi-Nagy et al., unpublished data). However, in1814 did establish a latent infection in the ganglia after corneal inoculation from which it could be reactivated. In this study, several HSV-1 strains were constructed with deletions in the VP16 transcriptional activation domain. These viruses were viable in cell culture, although some were significantly reduced in their ability to initiate infection. A deletion mutant completely lacking the activation domain of VP16 (RP5) was unable to replicate to any detectable level or to efficiently establish latent infections in the peripheral and central nervous systems of immunocompetent mice. However, similar to in1814, RP5 formed a slowly progressing persistent infection in immunocompromised nude mice. Thus RP5 is severely neuroattenuated in the murine model of HSV infection. However, the activation domain of VP16 is not essential for replication in the nervous system, since we observed a slow progressive infection persisting in the absence of an immune response.

Animals↗
PubMed1999

PCR-based quantitation of Cryptosporidium parvum in municipal water samples.

A PCR method for the quantitation of Cryptosporidium parvum oocysts in municipal drinking water samples was investigated. Quantitative PCR uses an internal standard (IS) template with unknown target numbers to compare to standards of known concentrations in a standard curve. The IS template was amplified using the same primers used to amplify a portion of a 358 bp gene fragment that encodes a repetitive oocyst wall protein in C. parvum. Municipal water samples spiked with known numbers of C. parvum oocysts were tested by quantitative PCR using the IS and the Digene SHARP Signal System Assay for PCR product detection. The absorbance readings for target DNA and IS templates versus the number of molecules of the target DNA were plotted to generate standard curves for estimating oocyst numbers. The method allowed the quantitation of oocysts from log 3 to log 5 spiked into municipal water samples.

Animals↗
PubMed1999

[Allergy to squid and acari in a child].

UNLABELLED: Anaphylactic reactions after consumption of squid by patients sensitized to house dust mites have been reported several times. CASE REPORT: A child allergic to dust mites developed an angioneurotic edema after eating squid. An immunoallergological assessment, including the prick test, labial test and IgE RAST revealed an allergy associated to both dust mites and squid. CONCLUSIONS: In light of the potential seriousness of anaphylactic reactions, parents of children allergic to dust mites and these children should be made aware of the increased risk of allergies to squid that they may face.

Acari↗
PubMed1999

Mutations in the gene encoding the human matrix Gla protein cause Keutel syndrome.

Keutel syndrome (KS, MIM 245150) is an autosomal recessive disorder characterized by abnormal cartilage calcification, peripheral pulmonary stenosis and midfacial hypoplasia. A genome search using homozygosity mapping provided evidence of linkage to chromosome 12p12.3-13.1 (maximum multipoint lod score, 4.06). MGP was a candidate on the basis of its localization to this chromosomal region and the known function of its protein. MGP maps to chromosome 12p near D12S363. Human MGP is a 10-kD skeletal extracellular matrix (ECM) protein that consists of an 84-aa mature protein and a 19-aa transmembrane signal peptide. It is a member of the Gla protein family, which includes osteocalcin, another skeletal ECM protein, and a number of coagulation factors (factors II, VII, IX, X and proteins S and C). All members of this family have glutamic acid residues modified to gamma-carboxyglutamic acids (Gla) by a specific gamma-carboxylase using vitamin K as a cofactor. The modified glutamic acid residues of Gla proteins confer a high affinity for mineral ions such as calcium, phosphate and hydroxyapatite crystals, the mineral components of the skeletal ECM. The pattern and tissue distribution of Mgp expression in mice suggest a role for Mgp in regulating ECM calcification. Mglap-deficient mice (Mglap-/-) have been reported to have inappropriate calcification of cartilage. Mutational analysis of MGP in three unrelated probands identified three different mutations: c.69delG, IVS1-2A-->G and c.113T-->A. All three mutations predict a non-functional MGP. Our data indicate that mutations in MGP are responsible for KS and confirm its role in the regulation of extracellular matrix calcification.

Abnormalities, Multiple↗
PubMed1998

Mass spectrometric and thermodynamic studies reveal the role of water molecules in complexes formed between SH2 domains and tyrosyl phosphopeptides.

BACKGROUND: SH2 domains have a fundamental role in signal transduction. These domains interact with proteins containing phosphorylated tyrosine residues and, in doing so, mediate the interactions of proteins involved in tyrosine kinase signalling. The issue of specificity in SH2 domain interactions is therefore of great interest in terms of understanding tyrosine kinase signal-transduction pathways and in the discovery of drugs to inhibit them. Water molecules are found at the interfaces of many complexes, however, to date little attention has been paid to their role in dictating specificity. RESULTS: Here we use a combination of nanoflow electrospray ionization mass spectrometry (ESI-MS), isothermal titration calorimetry and structural data to investigate the effect of water molecules in complexes formed between the SH2 domain of tyrosine kinase Src and tyrosyl phosphopeptides. Binding studies have been performed using a series of different peptides that were selected to allow changes in the water content at the complex interface and demonstrate changes in specificity. ESI-MS enables quantification of the number of water molecules that interact with a higher affinity than those generally found solvating the biomolecular complex. CONCLUSIONS: Comparing the interactions of different peptides, we show that an intricate network of water molecules have a key role in dictating specificity. The use of mass spectrometry to quantify tightly bound water molecules may prove of general use in structural biology, where an independent determination of the water molecules associated with a structure would be advantageous. Furthermore, the ability to assess whether given water molecules are important in high-affinity binding could make this method a precious tool in drug design.

Crystallography, X-Ray↗
PubMed1997

The expression of a novel, epithelium-specific ets transcription factor is restricted to the most differentiated layers in the epidermis.

Ets proteins have been implicated in the regulation of gene expression during a variety of biological processes, including growth control, differentiation, development and transformation. More than 35 related proteins containing the 'ets domain' have now been found which specifically interact with DNA sequences encompassing the core tetranucleotide GGAA. Although ets responsive genes have been identified in the epidermis, little is known about their distribution and function in this tissue. We have now demonstrated that epidermis and cultured epidermal keratinocytes synthesize numerous ets proteins. The expression of some of these proteins is regulated as a function of differentiation. Among these is a novel ets transcription factor with a dual DNA-binding specificity, which we have called jen. The expression of jen is not only epithelial specific, but it is the only ets protein so far described, and one of the very few transcription factors whose expression is restricted to the most differentiated epidermal layers. We show that two epidermal marker genes whose expression coincides with that of jen are transregulated by this protein in a complex mode which involves interactions with other transcriptional regulators such as Sp1 and AP1.

Adult↗