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Biomedical subjects

M Dean

Publications and source records attributed to M Dean.

At least 109 records · Page 6Linked to original sources
PubMed1999

Comparative molecular genetic profiles of anaplastic astrocytomas/glioblastomas multiforme and their subsequent recurrences.

Malignant glial tumors (anaplastic astrocytomas and glioblastomas multiforme) arise mostly either from the progression of low grade precursor lesions or rapidly in a de novo fashion and contain distinct genetic alterations. There is, however, a third subset of malignant gliomas in which genetic lesions remain to be identified. Following surgical resection, all gliomas appear to have an inherent tendency to recur. Comparative molecular analysis of ten primary malignant gliomas (three anaplastic astrocytomas and seven glioblastomas multiforme) with their recurrences identified two distinct subgroups of recurrent tumors. In one group, primary tumors harbored genetic aberrations frequently associated with linear progression or de novo formation pathways of glial tumorigenesis and maintained their genetic profiles upon recurrence. In the other subset with no detectable known genetic mutations at first presentation, the recurrent tumors sustained specific abnormalities associated with pathways of linear progression or de novo formation. These included loss of genes on chromosomes 17 and 10, mutations in the p53 gene, homozygous deletion of the DMBTA1 and p16 and/ or p15 genes and amplification and/or overexpression of CDK4 and alpha form of the PDGF receptor. Recurrent tumors from both groups also displayed an abnormal expression profile of the metalloproteinase, gel A, and its inhibitor, TIMP-2, consistent with their highly invasive behavior. Delineation of the molecular differences between malignant glioblastomas and their subsequent recurrences may have important implications for the development of rational clinical approaches for this neoplasm that remains refractory to existing therapeutic modalities.

Cell Cycle Proteins↗
PubMed1999

Molecular cloning of cDNAs which are highly overexpressed in mitoxantrone-resistant cells: demonstration of homology to ABC transport genes.

Reports of multiple distinct mitoxantrone-resistant sublines without overexpression of P-glycoprotein or the multidrug-resistance associated protein have raised the possibility of the existence of another major transporter conferring drug resistance. In the present study, a cDNA library from mitoxantrone-resistant S1-M1-80 human colon carcinoma cells was screened by differential hybridization. Two cDNAs of different lengths were isolated and designated MXR1 and MXR2. Sequencing revealed a high degree of homology for the cDNAs with Expressed Sequence Tag sequences previously identified as belonging to an ATP binding cassette transporter. Homology to the Drosophila white gene and its homologues was found for the predicted amino acid sequence. Using either cDNA as a probe in a Northern analysis demonstrated high levels of expression in the S1-M1-80 cells and in the human breast cancer subline, MCF-7 AdVp3000. Levels were lower in earlier steps of selection, and in partial revertants. The gene is amplified 10-12-fold in the MCF-7 AdVp3000 cells, but not in the S1-M1-80 cells These studies are consistent with the identification of a new ATP binding cassette transporter, which is overexpressed in mitoxantrone-resistant cells.

ATP-Binding Cassette Transporters↗
PubMed1999

Evaluation of the Best disease gene in patients with age-related macular degeneration and other maculopathies.

Vitelliform macular dystrophy (VMD2, Best disease, MIM153700) is an early onset, autosomal, dominant macular degeneration characterized by the deposition of lipofuscin-like material within and below the retinal pigment epithelium (RPE); it is associated with degeneration of the RPE and overlying photoreceptors. Recently, we cloned the gene bestrophin, which is responsible for the disease, and identified a number of causative mutations in families with VMD2. Here, we report that the analysis of bestrophin in a collection of 259 age-related macular degeneration (AMD) patients provides evidence that mutations in the Best disease gene do not play a significant role in the predisposition of individuals to AMD. However, our results suggest that, in addition to Best disease, mutations within the bestrophin gene could be responsible for other forms of maculopathy with phenotypic characteristics similar to Best disease and for other diseases not included in the VMD category.

Adult↗
PubMed1999

The rod photoreceptor ATP-binding cassette transporter gene, ABCR, and retinal disease: from monogenic to multifactorial.

The ABCR gene encodes a rod photoreceptor specific ATP-binding cassette transporter. Mutations in ABCR are associated with at least four inherited retinal dystrophies: Stargardt disease, Fundus Flavimaculatus, cone-rod dystrophy, and retinitis pigmentosa. A statistically significant increase in heterozygous ABCR alterations has been identified in patients with age-related macular degeneration (AMD). A pedigree is described which manifests both Stargardt disease and AMD in which an ABCR mutation cosegregates with both disease phenotypes. These data from this case report support the hypothesis that ABCR is a dominant susceptibility locus for AMD. Recent work regarding ABCR is reviewed and a model is presented in which decreased ABCR function correlates with severity of retinal disease.

ATP-Binding Cassette Transporters↗
PubMed1999

Conformational stability of human erythrocyte transglutaminase. Patterns of thermal unfolding at acid and alkaline pH.

Tissue-type transglutaminase is irreversibly inactivated during heat treatment. The rate of inactivation is low at pH 7.5; it increases slightly at acid pH (6.1) but much more at alkaline pH (9.0-9.5), suggesting that specific effects take place in the alkaline range, possibly in relation to decreased stability of the transition-state intermediate as pH is raised above 9.0. Differential scanning calorimetry experiments indicate that thermal unfolding of the protein occurs with two separate transitions, involving independent regions of the enzyme. They are assigned to domains 1 and 2 and domains 3 and 4, respectively, by a combination of calorimetric and spectroscopic techniques. When considering the effects of pH, we noted that transglutaminase was unfolded via different pathways at the different pH values considered. At acid pH, the whole structure of the protein was lost irreversibly, with massive aggregation. At neutral and, even more so, at alkaline pH, aggregation was absent (or very limited at high protein concentration) and the loss of secondary structure was dependent on the ionization state of crucial lysine residues. Unfolding at pH 9.5 apparently chiefly involved the N-terminal region, as testified by changes in protein intrinsic fluorescence. In addition, the C-terminal region was destabilized at each pH value tested during thermal unfolding, as shown by digestion with V8 proteinase, which is inactive on the native protein. Evidence was obtained that the N-terminal and C-terminal regions interact with each other in determining the structure of the native protein.

Calorimetry↗
PubMed1999

Genotype/Phenotype analysis of a photoreceptor-specific ATP-binding cassette transporter gene, ABCR, in Stargardt disease.

Mutation scanning and direct DNA sequencing of all 50 exons of ABCR were completed for 150 families segregating recessive Stargardt disease (STGD1). ABCR variations were identified in 173 (57%) disease chromosomes, the majority of which represent missense amino acid substitutions. These ABCR variants were not found in 220 unaffected control individuals (440 chromosomes) but do cosegregate with the disease in these families with STGD1, and many occur in conserved functional domains. Missense amino acid substitutions located in the amino terminal one-third of the protein appear to be associated with earlier onset of the disease and may represent misfolding alleles. The two most common mutant alleles, G1961E and A1038V, each identified in 16 of 173 disease chromosomes, composed 18.5% of mutations identified. G1961E has been associated previously, at a statistically significant level in the heterozygous state, with age-related macular degeneration (AMD). Clinical evaluation of these 150 families with STGD1 revealed a high frequency of AMD in first- and second-degree relatives. These findings support the hypothesis that compound heterozygous ABCR mutations are responsible for STGD1 and that some heterozygous ABCR mutations may enhance susceptibility to AMD.

ATP-Binding Cassette Transporters↗
PubMed1999

Genetics of HIV-1 infection: chemokine receptor CCR5 polymorphism and its consequences.

The chemokine receptor gene, CCR5, has become a central theme in studies of host genetic effects on HIV-1 pathogenesis ever since the discovery that the CCR5 molecule serves as a major cell surface co-receptor for the virus. A growing number of genetic variants within the coding and 5' regulatory region of CCR5 have been identified, several of which have functional consequences for HIV-1 pathogenesis. Here we review the CCR5 literature describing CCR5 polymorphism and the functional ramifications that several of these variants have on HIV-1 infection and progression to AIDS. The multiplicity of CCR5 genetic effects on HIV-1 disease underscores the critical importance of this gene in controlling AIDS pathogenesis and provides the logic for develop-ment of therapeutic strategies that target the interaction of HIV-1 envelope and CCR5 in HIV-1 associated disease.

Genetic Variation↗
PubMed1999

Mutation of a putative mitochondrial iron transporter gene (ABC7) in X-linked sideroblastic anemia and ataxia (XLSA/A).

X-linked sideroblastic anemia and ataxia (XLSA/A) is a recessive disorder characterized by an infantile to early childhood onset of non-progressive cerebellar ataxia and mild anemia with hypochromia and microcytosis. A gene encoding an ATP-binding cassette (ABC) transporter was mapped to Xq13, a region previously shown by linkage analysis to harbor the XLSA/A gene. This gene, ABC7, is an ortholog of the yeast ATM1 gene whose product localizes to the mitochondrial inner membrane and is involved in iron homeostasis. The full-length ABC7 cDNA was cloned and the entire coding region screened for mutations in a kindred in which five male members manifested XLSA/A. An I400M variant was identified in a predicted transmembrane segment of the ABC7 gene in patients with XLSA/A. The mutation was shown to segregate with the disease in the family and was not detected in at least 600 chromosomes of general population controls. Introduction of the corresponding mutation into the Saccharomyces cerevisiae ATM1 gene resulted in a partial loss of function of the yeast Atm1 protein. In addition, the human wild-type ABC7 protein was able to complement ATM1 deletion in yeast. These data indicate that ABC7 is the causal gene of XLSA/A and that XLSA/A is a mitochondrial disease caused by a mutation in the nuclear genome.

ATP-Binding Cassette Transporters↗
PubMed1999

Tyramide signal amplification (TSA)-FISH applied to mapping PCR-labeled probes less than 1 kb in size.

Tyramide signal amplification (TSA)-FISH was used to map one mouse and two human DNA probes of less than 1 kb in size. The two human probes were 319 and 608 bp, and the mouse probe was 855 bp. Probes, made from PCR products, were labeled by incorporating biotin-11-dUTP (human) and biotin-16-dUTP (mouse) during PCR amplification. Signals were readily observed in both interphase and metaphase cells following TSA-FISH for all three genes, whereas conventional FISH experiments produced no signals. The two human ATP-binding cassette (ABC) genes, EST883227 (GenBank Accession No. AA243820) and EST990006 (GenBank Accession No. AA348546), mapped to human chromosomes 7p21 and 17q25. The mouse gene, cmyc (exon 2) mapped to band D2 of mouse chromosome 15. These findings demonstrate the ability of this technique to map small probes (PCR products and expressed sequence tags) of less than 1 kb through highly increased signal amplification.

Animals↗
PubMed1998

Cancer as a complex developmental disorder--nineteenth Cornelius P. Rhoads Memorial Award Lecture.

The processes of differentiation and tumorigenesis have been long thought to be connected. The recent identification of Patched, a gene essential for Drosophila embryonic development, as a tumor suppressor has focused attention on the concept that tumorigenesis involves abnormalities of development. In fact, a large number of genes in the signalling pathway of the Patched gene are either tumor suppressors or oncogenes. This supports the concept that growth control is a critical requirement of differentiation, and that aberrant cellular development can contribute to malignancy. Whereas the identification of genes that result in dominantly inherited cancer syndromes has played a vital role in understanding cancer, the vast majority of "sporadic" cancers have properties of a complex genetic disease. Approaches to identify common alleles in cancer-associated genes promise to increase our understanding of the disease and aid the rational design of preventative and therapeutic strategies.

Animals↗
PubMed1998

Genetic acceleration of AIDS progression by a promoter variant of CCR5.

The CCR5 gene encodes a cell surface chemokine receptor molecule that serves as the principal coreceptor, with CD4, for macrophage-tropic (R5) strains of human immunodeficiency virus-type 1 (HIV-1). Genetic association analysis of five cohorts of people with acquired immunodeficiency syndrome (AIDS) revealed that infected individuals homozygous for a multisite haplotype of the CCR5 regulatory region containing the promoter allele, CCR5P1, progress to AIDS more rapidly than those with other CCR5 promoter genotypes, particularly in the early years after infection. Composite genetic epidemiologic analyses of genotypes bearing CCR5P1, CCR5-Delta32, CCR2-64I, and SDF1-3'A affirmed distinct regulatory influences for each gene on AIDS progression. An estimated 10 to 17 percent of patients who develop AIDS within 3.5 years of HIV-1 infection do so because they are homozygous for CCR5P1/P1, and 7 to 13 percent of all people carry this susceptible genotype. The cumulative and interactive influence of these AIDS restriction genes illustrates the multigenic nature of host factors limiting AIDS disease progression.

Acquired Immunodeficiency Syndrome↗
PubMed1998

A human placenta-specific ATP-binding cassette gene (ABCP) on chromosome 4q22 that is involved in multidrug resistance.

We characterized a new human ATP-binding cassette (ABC) transporter gene that is highly expressed in the placenta. The gene, ABCP, produces two transcripts that differ at the 5' end and encode the same 655-amino acid protein. The predicted protein is closely related to the Drosophila white and yeast ADP1 genes and is a member of a subfamily that includes several multidrug resistance transporters. ABCP, white, and ADP1 all have a single ATP-binding domain at the NH2 terminus and a single COOH-terminal set of transmembrane segments. ABCP maps to human chromosome 4q22, between the markers D4S2462 and D4S1557, and the murine gene (Abcp) is located on chromosome 6 28-29 cM from the centromere. ABCP defines a new syntenic segment between human chromosome 4 and mouse chromosome 6. The abundant expression of this gene in the placenta suggests that the protein product has an important role in transport of specific molecule(s) into or out of this tissue.

ATP-Binding Cassette Transporters↗