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P Lichter

Publications and source records attributed to P Lichter.

At least 37 records · Page 2Linked to original sources
PubMed2001

Alterations of the tumor suppressor genes CDKN2A (p16(INK4a)), p14(ARF), CDKN2B (p15(INK4b)), and CDKN2C (p18(INK4c)) in atypical and anaplastic meningiomas.

We investigated 67 meningothelial tumors (20 benign meningiomas, 34 atypical meningiomas, and 13 anaplastic meningiomas) for losses of genetic information from chromosome arms 1p and 9p, as well as for deletion, mutation, and expression of the tumor suppressor genes CDKN2A (p16(INKa)/MTS1), p14(ARF), CDKN2B (p15(INK4b)/MTS2) (all located at 9p21) and CDKN2C (1p32). Comparative genomic hybridization and microsatellite analysis showed losses on 1p in 11 anaplastic meningiomas (85%), 23 atypical meningiomas (68%), and 5 benign meningiomas (25%). One atypical meningioma with loss of heterozygosity on 1p carried a somatic CDKN2C mutation (c.202C>T: R68X). Losses on 9p were found in five anaplastic meningiomas (38%), six atypical meningiomas (18%), and one benign meningioma (5%). Six anaplastic meningiomas (46%) and one atypical meningioma (3%) showed homozygous deletions of the CDKN2A, p14(ARF), and CDKN2B genes. Two anaplastic meningiomas carried somatic point mutations in CDKN2A (c.262G>T: E88X and c.262G>A: E88K) and p14(ARF) (c.305G>T: G102V and c.305G>A: G102E). One anaplastic meningioma, three atypical meningiomas, and one benign meningioma without a demonstrated homozygous deletion or mutation of CDKN2A, p14(ARF), or CDKN2B lacked detectable transcripts from at least one of these genes. Hypermethylation of CDKN2A, p14(ARF), and CDKN2B could be demonstrated in one of these cases. Taken together, our results indicate that CDKN2C is rarely altered in meningiomas. However, the majority of anaplastic meningiomas either show homozygous deletions of CDKN2A, p14(ARF), and CDKN2B, mutations in CDKN2A and p14(ARF), or lack of expression of one or more of these genes. Thus, inactivation of the G(1)/S-phase cell-cycle checkpoint is an important aberration in anaplastic meningiomas.

Adult↗
PubMed2001

Pbx4, a new Pbx family member on mouse chromosome 8, is expressed during spermatogenesis.

Members of the Pbx family are involved in a diverse range of developmental processes including axial patterning and organogenesis. Pbx functions are in part mediated by the interaction of Pbx proteins with members of the Hox and Meis/Prep families. We have identified a fourth mammalian Pbx family member. Pbx4 in the mouse and PBX4 in humans are located on chromosome 8 and chromosome 19, respectively. Pbx4 expression is confined to the testis, especially to spermatocytes in the pachytene stage of the first meiotic prophase.

Amino Acid Sequence↗
PubMed2001

MDM2 gene amplification and lack of p53 point mutations in Hodgkin and Reed-Sternberg cells: results from single-cell polymerase chain reaction and molecular cytogenetic studies.

Hodgkin's disease (HD) is the most common haematological malignancy after chronic lymphocytic leukaemia, but very little is known about its pathogenesis or the genetic events that contribute to the malignant phenotype of the tumour cells. p53 is assumed to play an important role in the pathogenesis of HD, based on the observation that p53 protein is frequently accumulated in Hodgkin and Reed-Sternberg (H & RS) cells. We investigated single H & RS cells from five different HD patients for point mutations at the genomic level using multiplex polymerase chain reaction amplification and subsequent sequencing. No point mutations were detected in 50 single H & RS cells analysed. Hence, accumulation of p53 protein cannot be explained by mutations within the gene. A genome-wide screening for genomic imbalances using comparative genomic hybridization revealed gain on chromosome 12q14, i.e. the mapping position of the MDM2 gene in several HD cases. Therefore, we assessed the copy number of the MDM2 gene using fluorescence in situ hybridization. In four out of six HD cases analysed, the copy number of the MDM2 gene was found to be increased. As gene amplification is frequently associated with protein overexpression, the observed accumulation of p53 in the nuclei of H & RS cells could be as a result of elevated MDM2 protein levels resulting in stabilization of p53 protein.

Adult↗
PubMed2000

Genomic aberrations and survival in chronic lymphocytic leukemia.

BACKGROUND: Fluorescence in situ hybridization has improved the detection of genomic aberrations in chronic lymphocytic leukemia. We used this method to identify chromosomal abnormalities in patients with chronic lymphocytic leukemia and assessed their prognostic implications. METHODS: Mononuclear cells from the blood of 325 patients with chronic lymphocytic leukemia were analyzed by fluorescence in situ hybridization for deletions in chromosome bands 6q21, 11q22-23, 13q14, and 17p13; trisomy of bands 3q26, 8q24, and 12q13; and translocations involving band 14q32. Molecular cytogenetic data were correlated with clinical findings. RESULTS: Chromosomal aberrations were detected in 268 of 325 cases (82 percent). The most frequent changes were a deletion in 13q (55 percent), a deletion in 11q (18 percent), trisomy of 12q (16 percent), a deletion in 17p (7 percent), and a deletion in 6q (7 percent). Five categories were defined with a statistical model: 17p deletion, 11q deletion, 12q trisomy, normal karyotype, and 13q deletion as the sole abnormality; the median survival times for patients in these groups were 32, 79, 114, 111, and 133 months, respectively. Patients in the 17p- and 11q-deletion groups had more advanced disease than those in the other three groups. Patients with 17p deletions had the shortest median treatment-free interval (9 months), and those with 13q deletions had the longest (92 months). In multivariate analysis, the presence or absence of a 17p deletion, the presence or absence of an 11q deletion, age, Binet stage, the serum lactate dehydrogenase level, and the white-cell count gave significant prognostic information. CONCLUSIONS: Genomic aberrations in chronic lymphocytic leukemia are important independent predictors of disease progression and survival. These findings have implications for the design of risk-adapted treatment strategies.

Adult↗
PubMed2000

BCMSUN, a candidate gene for B-cell chronic lymphocytic leukemia and mantle-cell lymphoma, has an independently expressed homolog on 1p22-p31, BCMSUN-like.

The most frequent chromosomal imbalance in B-cell chronic lymphocytic leukemia (B-CLL) and mantle-cell lymphoma (MCL) is loss of material from 13q14.3. BCMSUN (previously Leu2, t4, cDNA 1B4) is one of 3 proposed candidate genes isolated from the minimally deleted region. We identified a homolog of BCMSUN, termed BCMSUNL (for BCMSUN-like). Radiation-hybrid mapping with a PCR-amplified fragment and fluorescence in situ hybridization with 2 PAC clones containing coding information for BCMSUNL revealed its localization at 1p22-p31. Interphase fluorescence in situ hybridization, however, revealed that the BCMSUNL gene locus is not part of the critical deletion region of 1p22 in MCLs. Analysis of DNA sequences derived from the respective PAC clones and available in public databases uncovered an intronless structure of BCMSUNL. Compared to BCMSUN, the new gene lacks exon 2 and shows 90.3% homology on the nucleic acid level. Both genes are expressed in peripheral blood lymphocytes from healthy donors as well as B-CLL and MCL tumors, with retention of genetic material at 13q14.3. Therefore, analysis of the candidate tumor-suppressor gene BCMSUN at 13q14.3 must be based on assays that distinguish between the 2 homologous genes.

Base Sequence↗
PubMed2000

Low grade fibromyxoid sarcoma. a further low-grade soft tissue malignancy characterized by a ring chromosome.

Supernumerary rings in the context of a simple karyotype characterize several low-grade malignant tumors of soft tissue and bone. Low-grade fibromyxoid sarcoma is an uncommon low-grade sarcoma, the cytogenetics of which has not yet been reported. Here we describe the first molecular-cytogenetic characterization of a pulmonary metastasis of low-grade fibromyxoid sarcoma. The histology of the primary and recurrent tumors was consistent with the diagnosis of low-grade fibromyxoid sarcoma of the usual type, whereas the pulmonary metastasis was of the "giant rosettes" variant. Cytogenetic analysis revealed a ring chromosome. Because gain of material of chromosomes 7 and 16 was detected by CGH, the ring chromosome is assumed to be composed of material from these respective chromosomes.

Adult↗
PubMed2000

Functional characterization of the gene encoding RLIM, the corepressor of LIM homeodomain factors.

RLIM is a RING H2 zinc finger protein that acts as a negative coregulator for LIM homeodomain transcription factors. We have isolated genomic lambda clones that cover the entire mouse RLIM-encoding Rnf12 gene. The Rnf12 gene encompasses 20 kb and consists of at least five exons and four introns. Several transcriptional start sites within a 24-bp region were mapped around 300 nt upstream of the translational start site. Rnf12-specific mRNA can be detected in many tissues as revealed by Northern blot analysis. Transient cotransfections reveal that the proximal Rnf12 promoter can be activated in vitro by ubiquitously and more restrictively expressed transcription factors, some of which are known mediators of signal transduction pathways, e.g., mammalian Krüppel-like transcription factors, Sox and ets-related proteins, and RBP-J. We isolated a cDNA encoding human RLIM, which is highly conserved with mouse and chick RLIM. By fluorescence in situ hybridization and interspecific backcross analysis, we have localized the Rnf12 gene to the central regions of mouse and human chromosome X.

Animals↗
PubMed2000

Spatial distribution of GC- and AT-rich DNA sequences within human chromosome territories.

Previous topological analyses of DNA sequence organization in the interphase chromosome mainly focused on the spatial distribution of individual gene copies within chromosome territories. In order to achieve a more comprehensive view into the subchromosomal arrangement of DNA, we isolated the GC-richest/gene-richest fraction (H3 isochores) as well as AT-richest/gene-poorest fraction of human genomic DNA (L1+L2 isochores) and visualized the respective DNA within individual chromosome territories by means of dual-color FISH. Application of confocal laser scanning microscopy and dedicated 3D image analysis software, which differentiated territory subvolumes by peeling shells one voxel in width, revealed a significant difference in the intraterritorial distribution of these two DNA sequence classes. While the H3 isochores were found localized in all subvolumes of the territories at similar frequency, simultaneously detected L1+L2 isochores were observed more to the interior of the same chromosome territories. Thus the GC-rich sequences display a much higher variability in their intraterritorial localization than AT-rich DNA fragments.

Chromosomes, Human↗
PubMed2000

Mantle cell lymphoma is characterized by inactivation of the ATM gene.

In mantle cell lymphoma (MCL), the translocation t(11;14) is considered the cytogenetic hallmark of the disease. Recently, however, deletion of the chromosomal region 11q22-q23 has been identified as a frequent event in this type of cancer, indicating the existence of a pathogenically relevant tumor suppressor gene in this region. The deleted segment contains the ATM (ataxia telangiectasia mutated) gene. ATM is an interesting candidate as a tumor suppressor gene because constitutive inactivation of the gene predisposes ataxia telangiectasia patients to lymphoid malignancies. To assess the potential involvement of the gene in MCL lymphomagenesis, we performed mutation analysis of ATM in 12 sporadic cases of MCL, 7 of them with a deletion of one ATM gene copy, by using single-strand conformation polymorphism analysis of reverse transcription-PCR-amplified mRNA and subsequent DNA sequencing. In all seven cases containing a deletion of one ATM allele, a point mutation in the remaining allele was detected, which resulted in aberrant transcript splicing, truncation, or alteration of the protein. In addition, biallelic ATM mutations were identified in two MCLs that did not contain 11q deletions. Interestingly, in three cases analyzed, the ATM mutations detected in the tumor cells were not present in nonmalignant cells, demonstrating their somatic rather than germ-line origin. The inactivation of both alleles of the ATM gene by deletion and deleterious point mutation in the majority of cases analyzed indicates that ATM plays a role in the initiation and/or progression of MCL.

Alleles↗
PubMed2000

Genomic imbalances including amplification of the tyrosine kinase gene JAK2 in CD30+ Hodgkin cells.

Comparative genomic hybridization was applied for a comprehensive screening of frequently occurring net gains and losses of chromosomal subregions in small populations of CD30+ Hodgkin cells and their morphological variants. In 12 Hodgkin's lymphomas, recurrent gains were detected on chromosomal arms 2p, 9p, and 12q (in six, four, and five tumors, respectively) and distinct high-level amplifications were identified on chromosomal bands 4p16, 4q23-q24, and 9p23-p24. In Hodgkin cells with 9p23-p24 amplification, fluorescence in situ hybridization revealed an increased copy number of chromosomal sequences spanning the tyrosine kinase gene JAK2. Several of the imbalances described, in particular a gain in chromosomal arm 9p that includes JAK2 amplification, are similar to the genomic changes detected in primary mediastinal B-cell lymphoma.

Adolescent↗
PubMed2000

Primary structure, chromosomal mapping, expression and transcriptional activity of murine hepatocyte nuclear factor 4gamma.

We demonstrate the presence of a new member of the orphan nuclear receptor hepatocyte nuclear factor 4 (HNF4) subfamily in mouse which is genetically distinct from the previously characterized mouse HNF4alpha gene. The new member of the HNF4 subfamily shows highest amino acid identity, similar tissue distribution and syntenous chromosomal localization to the recently described human HNF4gamma (NR2A2), we therefore classify it as mouse HNF4gamma (mHNF4gamma). A combination of RT-PCR and immunohistochemical analysis showed expression of mHNF4gamma mRNA and protein in the endocrine pancreas, testes, kidney and gut. By co-transfection experiments, we show that mHNF4gamma is able to activate transcription, acting through binding sites that have been previously characterized as HNF4alpha binding sites. The presence of HNFgamma in human and mouse implies that a complex transcriptional network exists in higher vertebrates involving a number of HNF4 members with overlapping yet distinct function and tissue distribution.

Animals↗
PubMed2000

Retinoic acid differentiation of HL-60 cells promotes cytoskeletal polarization.

Retinoic acid (RA) treatment of HL-60 cells in vitro induces granulocytic differentiation, involving reorganization of the nucleus and cytoplasm, development of chemoattractant-directed migration, and eventual apoptosis. The present studies with HL-60/S4 cells document that major elements of the cytoskeleton are changed: actin increases by 50%; vimentin decreases by more than 95%. The cellular content of alpha-tubulin does not significantly change; but the centrosomal-microtubule (MT) array moves away from the lobulating nucleus. Cytoskeletal-modifying chemicals modulate this polarized reorganization: Taxol and cytochalasin D enhance centrosome movement; nocodazole reverses it. Cytoskeletal-modifying chemicals do not appear to affect nuclear lobulation or the integrity of envelope-limited chromatin sheets (ELCS). Employing bcl-2-overexpressing HL-60 cells permitted demonstration of nuclear lobulation, ELCS formation, and centrosome-MT movement concomitantly during RA-induced differentiation, implying independence between the cellular reorganization and apoptotic programs. RA appears to promote an inherent potential in HL-60 cells for cytoskeletal polarization, likely to be important for chemoattractant-directed cell migration, an established characteristic of mature granulocytes.

Actins↗
PubMed2000

Risk of false positive results in comparative genomic hybridization.

Comparative genomic hybridization, a widely used method for screening for genomic imbalances, suffers from a lack of standardized evaluation. In order to compare a recently proposed data-driven procedure with the commonly used fixed cutoff values, we tested 257 events by both procedures as well as by fluorescence in situ hybridization using selected probes. With the data-driven procedure, a much higher fraction (42/218 vs. 8/218) of false positive results was obtained, whereas a higher sensitivity with respect to the detection of imbalances (30/39 vs. 19/39) was reached. Based on the significantly higher positive likelihood ratios and the positive predictive value, we strongly recommend the use of fixed diagnostic thresholds, because the alternative procedure generates an unacceptably high portion of incorrectly scored chromosomal imbalances. Genes Chromosomes Cancer 28:353-357, 2000.

Chromosome Aberrations↗
PubMed2000

In vivo observation of a nuclear channel-like system: evidence for a distinct interchromosomal domain compartment in interphase cells.

We have investigated the interchromosomal domain compartment in living cells by transfecting cDNA coding for Xenopus vimentin, engineered to contain a nuclear localization signal (NLS), coupled to the green fluorescent protein. In human vimentin-free SW13 cells, this chimeric protein was deposited in body-like "dots" both at 37 degrees C, the nonpermissive temperature for assembly of the amphibian vimentin, and 28 degrees C, the optimal temperature for Xenopus vimentin assembly, indicating that the chimeric protein was assembly incompetent. However, when transfected into a subclone stably expressing Xenopus NLS-vimentin (SW13-SC), the chimeric protein incorporated, as a fluorescent tracer, into the structures formed by NLS-vimentin and allowed us to visualize the outgrowth of the vimentin fibers after a temperature shift to 28 degrees C in living cells. In particular, we followed the time-dependent outgrowth of fibers from nuclear dots, first connecting two dots each and with time three and more, eventually generating a spatially restricted fiber system consisting of few loop-like arrays traversing the nucleus. Virtually identical results were obtained when the temperature was lowered only to 30 and 32 degrees C, respectively. An engineered human NLS-vimentin, without need for temperature shift, formed seemingly identical patterns of nuclear fibrils at 37 degrees C in three additionally transfected human cell lines: MCF-7, PLC, and HeLa. When the epithelial cytokeratin pair 8 and 18 was expressed in the nucleus via an engineered NLS in the cytokeratin 18 gene, more network-like, extended filament arrays were generated. Notably, in cotransfection experiments with Xenopus NLS-vimentin, we observed that the formation of these cytokeratin networks at 37 degrees C initiated from dots that nearly entirely colocalized with the aggregated amphibian NLS-vimentin. After a shift to 28 degrees C, extending Xenopus NLS-vimentin and cytokeratin filaments frequently followed the same path through the nucleus. These data indicate that interphase cells contain a seemingly equivalent, accessible interchromosomal space.

Actin Cytoskeleton↗