Biomedical subjects

G Kremmidiotis

Publications and source records attributed to G Kremmidiotis.

11 recordsLinked to original sources

PubMed2001

Neuronal sodium-channel alpha1-subunit mutations in generalized epilepsy with febrile seizures plus.

Generalized epilepsy with febrile seizures plus (GEFS+) is a familial epilepsy syndrome characterized by the presence of febrile and afebrile seizures. The first gene, GEFS1, was mapped to chromosome 19q and was identified as the sodium-channel beta1-subunit, SCN1B. A second locus on chromosome 2q, GEFS2, was recently identified as the sodium-channel alpha1-subunit, SCN1A. Single-stranded conformation analysis (SSCA) of SCN1A was performed in 53 unrelated index cases to estimate the frequency of mutations in patients with GEFS+. No mutations were found in 17 isolated cases of GEFS+. Three novel SCN1A mutations-D188V, V1353L, and I1656M-were found in 36 familial cases; of the remaining 33 families, 3 had mutations in SCN1B. On the basis of SSCA, the combined frequency of SCN1A and SCN1B mutations in familial cases of GEFS+ was found to be 17%.

Amino Acid Sequence↗

PubMed2000

Common chromosomal fragile site FRA16D sequence: identification of the FOR gene spanning FRA16D and homozygous deletions and translocation breakpoints in cancer cells.

Fluorescence in situ hybridization of a tile path of DNA subclones has previously enabled the cyto-genetic definition of the minimal DNA sequence which spans the FRA16D common chromosomal fragile site, located at 16q23.2. Homozygous deletion of the FRA16D locus has been reported in adenocarcinomas of stomach, colon, lung and ovary. We have sequenced the 270 kb containing the FRA16D fragile site and the minimal homozygously deleted region in tumour cells. This sequence enabled localization of some of the tumour cell breakpoints to regions which contain AT-rich secondary structures similar to those associated with the FRA10B and FRA16B rare fragile sites. The FRA16D DNA sequence also led to the identification of an alternatively spliced gene, named FOR (fragile site FRA16D oxidoreductase), exons of which span both the fragile site and the minimal region of homozygous deletion. In addition, the complete DNA sequence of the FRA16D-containing FOR intron reveals no evidence of additional authentic transcripts. Alternatively spliced FOR transcripts (FOR I, FOR II and FOR III) encode proteins which share N-terminal WW domains and differ at their C-terminus, with FOR III having a truncated oxidoreductase domain. FRA16D-associated deletions selectively affect the FOR gene transcripts. Three out of five previously mapped translocation breakpoints in multiple myeloma are also located within the FOR gene. FOR is therefore the principle genetic target for DNA instability at 16q23.2 and perturbation of FOR function is likely to contribute to the biological consequences of DNA instability at FRA16D in cancer cells.

Alternative Splicing↗

PubMed1999

The Batten disease gene product (CLN3p) is a Golgi integral membrane protein.

Batten disease (juvenile neuronal ceroid lipofuscinosis) is a recessive neurodegenerative disorder of childhood. The gene, CLN3, was recently identified and found to encode a novel 438 amino acid protein of unknown function. In order to gain insight into the function of the Batten disease protein (CLN3p), we investigated its subcellular localization. Protein constructs incorporating CLN3p fused to the green fluorescence protein or an eight amino acid peptide tag were transiently expressed in fibroblasts, HeLa and COS-7 cells. A juxtanuclear, asymmetric localization pattern was observed that correlated with the Golgi apparatus in all three cell types. However, a proportion of transiently transfected cells exhibited a punctate vesicular distribution throughout the cytoplasm in addition to or without the Golgi localization. In order to account for localization patterns arising from intracellular protein transport disruption due to exaggerated overexpression in transiently transfected cells, we isolated a stably transfected cell line expressing only one copy of the CLN3 -GFP DNA construct. Fluorescence and biochemical analyses using this cell line demonstrated that CLN3p is an integral membrane protein that localizes primarily in the Golgi apparatus. The functional implications of this finding are discussed.

Animals↗

PubMed1998

Localization of human cadherin genes to chromosome regions exhibiting cancer-related loss of heterozygosity.

This report presents the chromosomal localization of cadherin genes. Cadherins are cellular adhesion molecules. Since disturbance of intracellular adhesion is important for invasion and metastasis of tumor cells, cadherins are considered prime candidates for tumor suppressor genes. A variety of solid tumors show loss of heterozygosity of the long arm of chromosome 16, which is indicative of the potential location of tumor suppressor genes. Refined and new localizations of six cadherin genes (CDH3, 5, 8, 11, 13, and 15) to the long arm of chromosome 16 are shown. CDH15 was localized to 16q24.3, in a region that exhibits loss of heterozygosity in a number of sporadic breast cancer tumors. Previous localization of CDH13 (H-cadherin) to 16q24 suggested this gene as a tumor suppressor candidate in the 16q24.3 loss of heterozygosity region; however, refined mapping presented in this report localizes CDH13 proximal to this region. A human EST homologous to the chicken cadherin-7 was partially sequenced and found to represent a new human cadherin. This cadherin mapped to chromosome 18q22-q23, a region that exhibits loss of heterozygosity in head and neck squamous cell carcinomas. CDH16 was localized to 8q22.1, a region exhibiting loss of heterozygosity in adult acute myeloid leukemia.

Breast Neoplasms↗

PubMed1998

Heterogeneity of CD44 expression among human B-cell subpopulations.

CD44 is a widely distributed cell surface glycoprotein that participates in a number of cellular adhesion and signal transduction processes. Germinal center B cells express very low levels of CD44, whereas their precursors and differentiation products express much higher levels. In immunofluorescence studies comparing 20 antibodies classified as being against the hematopoietic isoform of CD44, one antibody, A1G3, was unreactive with germinal center B cells, whereas the other antibodies showed low intensity but definite reactivity. Western blotting and sequential immunoprecipitation studies of lysates from density-separated lymphocyte fractions showed two bands that were differentially expressed and reacted differently with A1G3 compared with the other CD44 antibodies. These results suggest that germinal center B cells and non-germinal center B cells express different forms of CD44. Of 21 malignant B-cell populations examined, 5 showed reactivity with a "standard" CD44 reagent and significantly reduced reactivity with A1G3, while one sample showed the opposite pattern and the remainder were positive for both reagents. Of 10 cell lines studied, 5 were differentially stained by A1G3 and a standard CD44 antibody. PCR amplification of reverse transcribed mRNA from sorted human tonsil B-cell subpopulations and Southern blotting showed that B cells express a number of splice isoforms of CD44. These results demonstrate that B cells express multiple forms of CD44; both splice insert isoforms and variants distinguished by A1G3; the form of CD44 expressed depends on B-cell differentiation state.

Antibodies, Monoclonal↗

PubMed1997

Genomic structure and complete nucleotide sequence of the Batten disease gene, CLN3.

We recently cloned a cDNA for CLN3, the gene for juvenile-onset neuronal ceroid lipofuscinosis or Batten disease. To resolve the genomic organization we used a cosmid clone containing CLN3 to sequence the entire gene in addition to 1.1 kb 5' of the start of the published CLN3 cDNA and 0.3 kb 3' to the polyadenylation site. CLN3 is organized into at least 15 exons spanning 15 kb and ranging from 47 to 356 bp. The 14 introns vary from 80 to 4227 bp, and all exon/intron junction sequences conform to the GT/AG rule. Numerous repetitive Alu elements are present within the introns and 5'- and 3'-untranslated regions. The 5' region of the CLN3 gene contains several potential transcription regulatory elements but no consensus TATA-1 box was identified. CLN3 is homologous to 27 deposited human ESTs, and sequence comparisons suggest alternative splicing of the gene and the existence of transcribed sequences upstream to the start of the published CLN3 cDNA.

Base Sequence↗

PubMed1997

Structure of the CLN3 gene and predicted structure, location and function of CLN3 protein.

The genomic sequence of the human CLN3 gene, which is defective in juvenile onset neuronal ceroid lipofuscinosis (Batten disease) is being delineated using a variety of methods. A Saccharomyces cerevisiae gene, YHC3 (for Yeast Homologue to human CLN3), which is highly similar to the human disease gene, has been identified by computer-aided homology searching. Topology predictions indicate the CLN3 protein contains six transmembrane segments. Most similarity between the human and yeast proteins lies either in the transmembrane segments or along one face of the predicted protein structure.

Adolescent↗

PubMed1995

Integration of transcript and genetic maps of chromosome 16 at near-1-Mb resolution: demonstration of a "hot spot" for recombination at 16p12.

A single mapping resource, a mouse/human somatic cell panel with average distance between breakpoints of 1.2 Mb and a potential resolution of 1 Mb, has been utilized to integrate the genetic map and a transcript map of human chromosome 16. This map includes 141 genetic markers and 200 genes and transcripts. The localization of four genes (CHEL3, TK2, TRG1, and MMP9) reported to map to chromosome 16 could not be confirmed, and for three of these localizations to other human chromosomes are reported. A correlation between genetic and physical distance over a region estimated to be 23 Mb on the short arm of chromosome 16 identified an interval demonstrating a greatly increased rate of recombination where, in females, 1 cM is equivalent to a physical distance of 100 kb.

Animals↗

PubMed1995

Changes in CD44 expression during B cell differentiation in the human tonsil.

CD44 is a widely distributed cell surface glycoprotein that has been implicated in a number of cellular adhesion processes and signal transduction events. These functional capabilities qualify CD44 as a potential mediator of contact-signaling events underlying the process of antigen-dependent B cell differentiation in secondary lymphoid tissues. We postulated that changes in the expression of CD44 during B cell differentiation reflect the cells' changing requirements for this receptor. It has been reported that germinal center B cells are low to negative for CD44 expression, implying that the receptor is lost upon activation. Correlation of the expression of CD44 with surface immunoglobulin and a number of B cell differentiation markers revealed a trimodal expression pattern. High levels of CD44 are expressed on resting IgD+/IgM+ cells. The receptor is still expressed at the early activation stage defined by the expression of CD23. At the early blast stage, when the blast marker CD38 appears on the cell surface and IgD and CD23 disappear, CD44 is downregulated. The majority of CD38+/IgM+ blasts and CD38+/Ig- centroblasts are CD44 low/negative. The receptor is re-upregulated at the point of transition from the centroblast to the centrocyte level. Centrocytes expressing IgG or IgA comprise CD44high and CD44low fractions. IgG+ or IgA+ cells at the postgerminal center stage express high levels of CD44. The functional implications of this expression pattern are discussed.

ADP-ribosyl Cyclase↗

PubMedDate not supplied

CD44.

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Alternative Splicing↗

PubMedDate not supplied

Characterization of a monoclonal antibody with CD44 like reactivity.

QE7.3E8 is a monoclonal antibody which precipitates two bands (90 and 160 kd) from a B cell line and four (90, 130, 146, and 160 kd) from monocytes. Whilst this immunoprecipitation pattern suggests that QE7.3E8 is a CD18 antibody, a number of other results are inconsistent with this interpretation. In particular, QE7.3E8 stains lymphoid tissue with a distribution clearly distinguishable from CD18 antibodies; it precipitates four bands from a T cell line which does not express the CD11b and CD11c alpha chains, and cross immunoprecipitation with QE7.3E8 and a CD11a antibody show that the molecules recognized by these antibodies are not associated. However, in tissue distribution and sequential precipitation experiments QE7.3E8 behaves like a CD44 antibody. CD44 identifies a single 85 kd protein, but high molecular weight complexes have been described, accounting for the multiple bands seen in immunoprecipitation studies. Sequential immunoprecipitation using QE7.3E8 and a Workshop-clustered monoclonal antibody (SBU 25-32) indicate that the QE7.3E8 reacts with the CD44 antigen.

Antibodies, Monoclonal↗