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P Lichter

Publications and source records attributed to P Lichter.

At least 73 records · Page 4Linked to original sources
PubMed1999

Spleen-specific expression of the malaria-inducible intronless mouse gene imap38.

We characterize the mouse gene imap38 and its inducibility by Plasmodium chabaudi malaria among different lymphoid tissues and mouse strains of different H-2 complex and non-H-2 background. Imap38 is a single copy gene assigned to chromosome 6B. It consists of only one exon of 1900 base pairs encoding a highly basic 25.8-kDa protein. Confocal laser scanning microscopy localizes differently tagged IMAP38 proteins in nuclei of transfected cells. Reporter gene assays reveal that the 1730-base pair 5'-flanking region, containing an RSINE1 repeat immediately adjacent to initiation site +1, exhibits promoter activity in nonmurine cells, while it is largely repressed in diverse mouse cell lines, which corresponds to the situation in mouse tissues. P. chabaudi malaria induces imap38 expression almost exclusively in the spleen but not in other lymphoid organs. Parasite lysates are able to induce imap38 in the spleen, but not in spleen cells ex vivo. Activation of spleen cells by LPS and other stimuli is not sufficient to induce imap38. Inducibility of imap38 requires signals from both parasites and the intact spleen, and it is controlled by genes of that non-H-2 background, which also controls development of protective immunity against P. chabaudi malaria.

5' Untranslated Regions↗
PubMed1999

Molecular characterization of a slowly gating human hyperpolarization-activated channel predominantly expressed in thalamus, heart, and testis.

Rhythmic activity of neurons and heart cells is endowed by pacemaker channels that are activated by hyperpolarization and directly regulated by cyclic nucleotides (termed HCN channels). These channels constitute a multigene family, and it is assumed that the properties of each member are adjusted to fit its particular function in the cell in which it resides. Here we report the molecular and functional characterization of a human subtype hHCN4. hHCN4 transcripts are expressed in heart, brain, and testis. Within the brain, the thalamus is the predominant area of hHCN4 expression. Heterologous expression of hHCN4 produces channels of unusually slow kinetics of activation and inactivation. The mean potential of half-maximal activation (V(1/2)) was -75.2 mV. cAMP shifted V(1/2) by 11 mV to more positive values. The hHCN4 gene was mapped to chromosome band 15q24-q25. The characteristic expression pattern and the sluggish gating suggest that hHCN4 controls the rhythmic activity in both thalamocortical neurons and pacemaker cells of the heart.

Amino Acid Sequence↗
PubMed1999

Somatic ATM mutations indicate a pathogenic role of ATM in B-cell chronic lymphocytic leukemia.

Deletion in chromosome bands 11q22-q23 is one of the most common chromosome aberrations in B-cell chronic lymphocytic leukemia (B-CLL). It is associated with extensive lymph node involvement and poor survival. The minimal consensus deletion comprises a segment, which contains the ATM gene presenting an interesting candidate gene, as mutations in ATM predispose A-T patients to lymphoid malignancies. To investigate a potential pathogenic role of ATM in B-cell tumorigenesis, we performed mutation analysis of ATM in 29 malignant lymphomas of B-cell origin (B-CLL = 27; mantle cell lymphoma, [MCL] = 2). Twenty-three of these carried an 11q22-q23 deletion. In five B-CLLs and one MCL with deletion of one ATM allele, a point mutation in the remaining allele was detected, which resulted in aberrant transcript splicing, alteration, or truncation of the protein. In addition, mutation analysis identified point mutations in three cases without 11q deletion: two B-CLLs with one altered allele and one MCL with both alleles mutated. In four cases analyzed, the ATM alterations were not present in the germ line indicating a somatic origin of the mutations. Our study demonstrates somatic disruption of both alleles of the ATM gene by deletion or point mutation and thus its pathogenic role in sporadic B-cell lineage tumors.

Ataxia Telangiectasia↗
PubMed1999

Strategies for the detection of disease genes in pancreatic cancer.

The present review summarizes our strategies aimed at identifying and characterizing genetic alterations occurring at the transcriptional and chromosomal level in pancreatic cancer. To study transcriptional alterations we have used a number of techniques including modified versions of differential hybridizations and cDNA RDA (representational difference analysis). These approaches have led to the identification of more than 500 genes with differential expression in pancreatic cancer. To study chromosomal aberrations occurring in pancreatic cancer tissues we used comparative genomic hybridization (CGH). This allowed the identification of a number of chromosomal regions containing putative tumor suppressor genes or oncogenes. Genes isolated in both approaches represent potential new disease genes for pancreatic cancer and are at present being characterized by individual or serial analysis.

Amino Acid Sequence↗
PubMed1999

Chromosome aberrations in B-cell chronic lymphocytic leukemia: reassessment based on molecular cytogenetic analysis.

In B-cell chronic lymphocytic leukemia (B-CLL) clonal chromosome aberrations are detected in approximately 40-50% of tumors when using conventional chromosome banding analysis. Most studies find trisomy 12 to be the most frequent chromosome aberration, followed by structural aberrations of the long arm of chromosomes 13 and 14. Trisomy 12 and the "14q+" marker are associated with shorter survival times, while the patients with 13q abnormalities have a favorable outcome, similar to those with a normal karyotype. The development of molecular cytogenetic techniques has greatly improved our ability to detect chromosome aberrations in tumor cells. Using fluorescence in situ hybridization, chromosome aberrations can be detected not only in dividing cells but also in interphase nuclei, an approach referred to as interphase cytogenetics. The prevalence of specific aberrations in B-CLL is currently being reassessed by interphase cytogenetics. By far the most frequent abnormality are deletions involving chromosome band 13q14, followed by deletions of the genomic region 11q22.3-q23.1, trisomy 12, deletions of 6q21-q23, and deletions/mutations of the TP53 tumor suppressor gene at 17p13. The evaluation of the true incidence of these aberrations now provides the basis for more accurate correlations with clinical characteristics and outcome. Deletions/mutations of the TP53 gene have been shown to be associated with resistance to treatment and to be an independent marker for poor survival. 11q deletions have been associated with extensive nodal involvement, rapid disease progression, and short survival times. Whether trisomy 12, 13q14, and 6q deletions have a prognostic impact awaits further study. The application of these molecular cytogenetic techniques will also contribute to the identification of the pathogenetically relevant genes that are affected by the chromosome aberrations in B-CLL.

Animals↗
PubMed1999

DNA chip technology ante portas.

The recent popularity of DNA chip technology has been fostered by the increasing demand for new diagnostic tools which allow the simultaneous analysis of large numbers of nucleic acid hybridization experiments in a timely fashion. The development of DNA chip-based assays has been strongly driven by modern approaches aiming at the comprehensive analysis of multiple gene mutations and expressed sequences. The broad range of current DNA chip applications include the detection of pathogens, the measurement of differences in the expression of genes between different cell populations, and the analysis of genomic alterations such as sequence and copy number alterations in disease-related genes and single nucleotide polymorphisms. We present an overview of the impact of DNA chip technology on the field of molecular medicine and discuss developments that can be expected in the near future.

Animals↗
PubMed1999

Incidence and clinical significance of 6q deletions in B cell chronic lymphocytic leukemia.

Deletions affecting the long arm of chromosome 6 (6q) are among the most commonly observed chromosomal aberrations in lymphoid malignancies and have been identified as adverse prognostic factor in subsets of tumors. Whereas at least two regions of minimal deletion have been established, one in 6q21-q23 and another in 6q25-q27, no tumor suppressor gene that might be involved in the pathogenesis of lymphoid malignancies has been so far identified from these segments. For B cell chronic lymphocytic leukemia (B-CLL) conflicting data have been reported regarding the incidence and prognostic significance of 6q deletions. In the current study we have used two YAC clones mapping to deletion regions in bands 6q21 and 6q27 as probes for fluorescence in situ hybridization (FISH) in a large series of B-CLL cases to analyze the incidence, localization and clinical significance of 6q aberrations. Among 285 patients with B-CLL studied we identified 21 cases (7%) with 6q deletions. All deletions were found with the probe mapping to 6q21 while the 6q27 region was deleted only in a third of these cases. Analysis of the clinical characteristics and laboratory parameters showed that the patients with 6q deletions had higher white blood cell counts and more extensive lymphadenopathy. However, the overall survival and the treatment-free intervals were similar in the two groups. We conclude that deletions in 6q21 occur in 7% of B-CLL and identify a subgroup of patients characterized by a larger tumor mass but no inferior outcome.

Chromosome Deletion↗
PubMed1999

Genomic organization of mouse gene zfp162.

We report the cloning and characterization of the alternatively spliced mouse gene zfp162, formerly termed mzfm, the homolog of the human ZFM1 gene encoding the splicing factor SF1 and a putative signal transduction and activation of RNA (STAR) protein. The zfp162 gene is about 14 kb long and consists of 14 exons and 13 introns. Comparison of zfp162 with the genomic sequences of ZFM1/SF1 revealed that the exon-intron structure and exon sequences are well conserved between the genes, whereas the introns differ in length and sequence composition. Using fluorescent in situ hybridization, the zfp162 gene was assigned to chromosome 19, region B. Screening of a genomic library integrated in lambda DASH II resulted in the identification of the 5'-flanking region of zfp162. Sequence analysis of this region showed that zfp162 is a TATA-less gene containing an initiator control element and two CCAAT boxes. The promoter exhibits the following motifs: AP-2, CRE, Ets, GRE, HNF5, MRE, SP-1, TRE, TCF1, and PU.1. The core promoter, from position -331 to -157, contains the motifs CRE, SP-1, MRE, and AP-2, as determined in transfected CHO-K1 cells and IC-21 cells by reporter gene assay using a secreted form of human placental alkaline phosphatase. The occurrence of PU.1/GRE supports the view that the zfp162 gene encodes a protein involved not only in nuclear RNA metabolism, as the human ZFM1/SF1, but also in as yet unknown macrophage-inherent functions.

Alternative Splicing↗
PubMed1999

Amplification and expression of cyclin D genes (CCND1, CCND2 and CCND3) in human malignant gliomas.

Malignant gliomas frequently show genetic aberrations of genes coding for cell cycle regulatory proteins involved in the control of G1/S phase transition. These include mutation and/or deletion of the retinoblastoma (RB1) gene, homozygous deletion of the CDKN2A and CDKN2B genes, as well as amplification and overexpression of the CDK4 and CDK6 genes. The D-type cyclins (cyclin D1, D2, and D3) promote cell cycle progression from G1 to S phase by binding to and activating the cyclin dependent kinases Cdk4 and Cdk6. Here, we have investigated a series of 110 primary malignant gliomas and 8 glioma cell lines for amplification and expression of the D-type cyclin genes CCND1 (11q13), CCND2 (12p13), and CCND3 (6p21). We found the CCND1 gene amplified and overexpressed in one anaplastic astrocytoma of our tumor series. Two glioblastomas and one anaplastic astrocytoma showed CCND2 gene amplification, but lacked significant overexpression of CCND2 transcripts. Amplification and overexpression of the CCND3 gene was detected in the glioblastoma cell line CCF-STTG1, as well as in one primary glioblastoma and in the sarcomatous component of one gliosarcoma. Our data thus suggest that amplification and increased expression of CCND1 and CCND3 contribute to the loss of cell cycle control in a small fraction of human malignant gliomas.

Blotting, Southern↗
PubMed1999

Chordoid glioma of the third ventricle: immunohistochemical and molecular genetic characterization of a novel tumor entity.

Chordoid glioma of the third ventricle was recently reported as a novel tumor entity of the central nervous system with characteristic clinical and histopathological features (Brat et al., J Neuropathol Exp Neurol 57: 283-290, 1998). Here, we report on a histopathological, immunohistochemical and molecular genetic analysis of five cases of this rare neoplasm. All tumors were immunohistochemically investigated for the expression of various differentiation antigens, the proliferation marker Ki-67, and a panel of selected proto-oncogene and tumor suppressor gene products. These studies revealed a strong expression of GFAP, vimentin, and CD34. In addition, most tumors contained small fractions of neoplastic cells immunoreactive for epithelial membrane antigen, S-100 protein, or cytokeratins. The percentage of Ki-67 positive cells was generally low (<5%). All tumors showed immunoreactivity for the epidermal growth factor receptor and schwannomin/merlin. There was no nuclear accumulation of the p53, p21 (Waf-1) and Mdm2 proteins. To examine genomic alterations associated with the development of chordoid gliomas, we screened 4 tumors by comparative genomic hybridization (CGH) analysis. No chromosomal imbalances were detected. More focussed molecular genetic analyses revealed neither aberrations of the TP53 and CDKN2A tumor suppressor genes nor amplification of the EGFR, CDK4, and MDM2 proto-oncogenes. Our data strongly support the hypothesis that chordoid glioma of the third ventricle constitutes a novel tumor entity characterized by distinct morphological and immunohistochemical features, as well as a lack of chromosomal and genetic alterations commonly found in other types of gliomas or in meningiomas.

Adult↗
PubMed1999

Association of genomic imbalances with resistance to therapeutic drugs in human melanoma cell lines.

The reason why human malignant melanomas respond poorly to chemotherapy is not known. In an attempt to identify genes responsible for such resistance or sensitivity to therapeutic drugs, we studied the parental human melanoma cell line MeWo, as well as eight drug-resistant sublines of MeWo. These have low and high levels of resistance to four chemotherapeutic drugs with different modes of action: Vindesine, cisplatin, fotemustine and etoposide. Comparative genomic hybridizations with genomic DNA from these cell lines as probes revealed a number of chromosome gains and losses which occurred upon selective pressure during development of the sublines. The MeWo subline with high resistance to the topoisomerase II inhibitor, etoposide, exhibited the highest number of acquired chromosome imbalances. Interestingly, the two lines with high resistance to cisplatin and fotemustine, respectively, shared three additional imbalances, loss of 9p, loss of distal 12p and gain on distal 15q. The importance of these coincident imbalances is discussed.

Aneuploidy↗
PubMed1999

Direct visual resolution of gene copy number in the human photopigment gene array.

PURPOSE: To visualize by direct fluorescent in situ hybridization the entire human visual pigment gene array on single X-chromosome fibers and to compare the results with values obtained by other molecular techniques. METHODS: The size of the opsin gene array on the X-chromosome in eight male subjects was investigated by (i) direct visual in situ hybridization (DIRVISH) on elongated DNA fibers: (ii) quantitation of genomic restriction fragments after Southern blot hybridization; (iii) quantitation of restriction fragment length polymorphism after PCR amplification (PCR/RFLP), and (iv) sizing of NotI fragments by pulsed field gel electrophoresis and Southern blot detection. Each male subject's color vision was assessed by Rayleigh matches on a Nagel Type 1 anomaloscope. RESULTS: The number of genes resolved by the DIRVISH protocol, which ranges from 1 to 6, agrees exactly with the gene array sizes obtained in the same male subjects from pulsed field gel electrophoresis, but differs from the estimates derived from the commonly used indirect Southern blot hybridization and PCR/RFLP quantitation methods. In particular, the PCR/RFLP method overestimates the copy number in all but the smallest arrays. CONCLUSIONS: Visualization of the X-chromosome opsin gene array by DIRVISH provides a new, direct method for obtaining exact copy numbers and helps to resolve the controversy about the range and the average visual pigment gene number in the human population in favor of smaller average array sizes.

Blotting, Southern↗
PubMed1999

Analysis of chromosomal imbalances in sporadic and NF1-associated peripheral nerve sheath tumors by comparative genomic hybridization.

Peripheral nerve sheath tumors arise either sporadically or in association with neurofibromatosis type 1 (von Recklinghausen's neurofibromatosis, NF1) or type 2. In this study, comprehensive screening for relative chromosome copy number changes was performed on 10 benign and 19 malignant peripheral nerve sheath tumors (MPNSTs) by applying comparative genomic hybridization (CGH). In benign tumors, no chromosomal imbalances were found by CGH, whereas in MPNSTs chromosomal gains and losses were frequently detected. No differences regarding the frequency and distribution of chromosomal imbalances were observed between the 13 sporadic and 6 NF1-associated MPNSTs analyzed. In both, the number of gains was significantly higher than the number of losses, suggesting a predominant role of proto-oncogene activation during MPNST progression. Candidate regions with potentially relevant proto-oncogenes included chromosomal bands 17q24-q25, 7p11-p13, 5p15, 8q22-q24, and 12q21-q24; those with putative tumor suppressor genes were 9p21-p24, 13q14-q22, and 1p. High-level amplifications were restricted to sporadic tumors and affected eight different chromosomal subregions. In three of these MPNSTs, identical subregions on chromosomal arms 5p and 12q were coamplified. This study revealed a number of new characteristic chromosomal imbalances and provides a basis for molecular identification of oncogenes and tumor suppressor genes of pathogenetic relevance in both sporadic and NF1-associated MPNSTs. Genes Chromosomes Cancer 25:362-369, 1999.

Adolescent↗
PubMed1999

Novel technology for detection of genomic and transcriptional alterations in pancreatic cancer.

AIM: The present review summarizes our strategies aimed at identifying and characterizing genetic alterations occurring at the transcriptional and chromosomal level in pancreatic cancer. METHODS: To study transcriptional alterations we have used a number of techniques including modified versions of differential hybridizations and cDNA-RDA (representational difference analysis). Comparative genomic hybridization (CGH) was used to study chromosomal aberrations occurring in pancreatic cancer tissues. RESULTS: The study of transcriptional alterations led to the identification of more than 500 genes with differential expression in pancreatic cancer. The sum of these alterations represented the first expression profile characteristic for pancreatic tumors. The CGH analysis allowed the identification of a number of chromosomal regions containing putative tumor suppressor genes or oncogenes. These regions are presently being characterized at the molecular level. In a first approach the myb-oncogene was identified as the relevant oncogene of an amplification on 6q occurring in up to 10% of pancreatic cancer patients. CONCLUSIONS: Genes isolated in both approaches represent potential new disease genes for pancreatic cancer and are at present being characterized by individual or serial analysis.

Chromosome Aberrations↗
PubMed1999

Retention of polysomy at 9p23-24 during karyotypic evolution in human breast cancer cell line COLO 824.

Somatic genetic alterations of 9p have been seen in a wide range of human cancers, including breast cancer. Loss of heterozygosity analysis of primary breast cancer tumors has revealed a high frequency of deletion of DNA from 9p21-22 encompassing the MTSI (P16/CDKN2A) gene. We report the approximately tenfold increase in copy number of DNA from 9p23-24, which is far distal to P16/CDKN2A in female breast cancer cell line COLO 824, as revealed by fluorescence in situ hybridization, comparative genomic hybridization, and microsatellite analysis. Amplification of DNA has been reported previously to encompass multiple sites of the genome of the breast cancer cell, but increase in DNA copy number has not been seen in distal 9p.

Aneuploidy↗
PubMed1998

Molecular cytogenetic characterization of a critical region in bands 7q35-q36 commonly deleted in malignant myeloid disorders.

Loss of chromosome 7 (-7) or deletion of the long arm (7q-) are recurring chromosome abnormalities in myeloid leukemias. The association of -7/7q- with myeloid leukemia suggests that these regions contain novel tumor suppressor gene(s), whose loss of function contribute to leukemic transformation or tumor progression. Based on chromosome banding analysis, two critical regions have been identified, one in band q22 and another in bands q32-q35. Presently there are no data available on the molecular delineation of the distal critical region. In this study we analyzed bone marrow and blood samples from 13 patients with myeloid leukemia (de novo myelodysplastic syndrome [MDS], n = 3; de novo acute myeloid leukemia [AML], n = 9; therapy-related (t-) AML, n = 1) which, on chromosome banding analysis, exhibited deletions (n = 12) or in one case a balanced translocation involving bands 7q31-qter using fluorescence in situ hybridization (FISH). As probes we used representative clones from a contig map of yeast artificial chromosome (YAC) clones that spans chromosome bands 7q31.1-qter. In the 12 cases with loss of 7q material, we identified a commonly deleted region of approximately 4 to 5 megabasepairs in size encompassing the distal part of 7q35 and the proximal part of 7q36. Furthermore, the breakpoint of the reciprocal translocation from the patient with t-AML was localized to a 1,300-kb sized YAC clone that maps to the proximal boundary of the commonly deleted region. Interestingly, in this case both homologs of chromosome 7 were affected: one was lost (-7) and the second exhibited the t(7q35). The identification and delineation of translocation and deletion breakpoints provides the first step toward the identification of the gene(s) involved in the pathogenesis of 7q35-q36 aberrations in myeloid disorders.

Chromosome Mapping↗