[Show abstract][Hide abstract] ABSTRACT: Gene amplification occurs in most solid tumors and is associated with poor prognosis. Amplification of 20q13.2 is common to several tumor types including breast cancer. The 1 Mb of sequence spanning the 20q13.2 breast cancer amplicon is one of the most exhaustively studied segments of the human genome. These studies have included amplicon mapping by comparative genomic hybridization (CGH), fluorescent in-situ hybridization (FISH), array-CGH, quantitative microsatellite analysis (QUMA), and functional genomic studies. Together these studies revealed a complex amplicon structure suggesting the presence of at least two driver genes in some tumors. One of these, ZNF217, is capable of immortalizing human mammary epithelial cells (HMEC) when overexpressed. In addition, we now report the sequencing of this region in human and mouse, and on quantitative expression studies in tumors. Amplicon localization now is straightforward and the availability of human and mouse genomic sequence facilitates their functional analysis. However, comprehensive annotation of megabase-scale regions requires integration of vast amounts of information. We present a system for integrative analysis and demonstrate its utility on 1.2 Mb of sequence spanning the 20q13.2 breast cancer amplicon and 865 kb of syntenic murine sequence. We integrate tumor genome copy number measurements with exhaustive genome landscape mapping, showing that amplicon boundaries are associated with maxima in repetitive element density and a region of evolutionary instability. This integration of comprehensive sequence annotation, quantitative expression analysis, and tumor amplicon boundaries provide evidence for an additional driver gene prefoldin 4 (PFDN4), coregulated genes, conserved noncoding regions, and associate repetitive elements with regions of genomic instability at this locus.
[Show abstract][Hide abstract] ABSTRACT: We have placed 7,600 cytogenetically defined landmarks on the draft sequence of the human genome to help with the characterization of genes altered by gross chromosomal aberrations that cause human disease. The landmarks are large-insert clones mapped to chromosome bands by fluorescence in situ hybridization. Each clone contains a sequence tag that is positioned on the genomic sequence. This genome-wide set of sequence-anchored clones allows structural and functional analyses of the genome. This resource represents the first comprehensive integration of cytogenetic, radiation hybrid, linkage and sequence maps of the human genome; provides an independent validation of the sequence map and framework for contig order and orientation; surveys the genome for large-scale duplications, which are likely to require special attention during sequence assembly; and allows a stringent assessment of sequence differences between the dark and light bands of chromosomes. It also provides insight into large-scale chromatin structure and the evolution of chromosomes and gene families and will accelerate our understanding of the molecular bases of human disease and cancer.
[Show abstract][Hide abstract] ABSTRACT: We show here that quantitative measurement of DNA copy number across amplified regions using array comparative genomic hybridization (CGH) may facilitate oncogene identification by providing precise information on the locations of both amplicon boundaries and amplification maxima. Using this analytical capability, we resolved two regions of amplification within an approximately 2-Mb region of recurrent aberration at 20q13.2 in breast cancer. The putative oncogene ZNF217 (ref. 5) mapped to one peak, and CYP24 (encoding vitamin D 24 hydroxylase), whose overexpression is likely to lead to abrogation of growth control mediated by vitamin D, mapped to the other.
[Show abstract][Hide abstract] ABSTRACT: Comprehensive information about the molecular cytogenetic changes in metastases of colorectal cancer is not yet available. To define such changes in metastases, we measured relative DNA sequence copy numbers by comparative genomic hybridization (CGH). Samples from 27 liver metastases and 6 synchronous primary tumors were analyzed. An average of 9.9 aberrations per tumor was found in the metastases. Gains of chromosome arms 20q (85%), 13q (48%), 7p (44%), and 8q (44%) and losses of chromosome arms 18q (89%), 8p (59%), 1p (56%), and 18p (48%) were detected most frequently. Chromosomes 14 and 15 were lost in 26% and 30% of the metastases, respectively. No consistent differences were observed between primary tumors and synchronous metastases. Fluorescence in situ hybridization (FISH) was used for further characterization of gains of chromosome arm 20q. Touch preparations of 13 tumors that had demonstrated 20q gain with CGH were examined with FISH by use of a set of probes mapping to different parts of 20q. A probe for 20p was used as a reference. FISH showed relative gain of at least one 20q locus in 12 of the tumors. High-level gains were detected in 38% of the tumors, preferentially for probes mapping to band 20q13. Our CGH data indicate that colorectal metastases show chromosomal changes similar to those that have been reported for primary tumors. Chromosomal losses were seen at higher frequency, particularly for chromosomes 14 and 15. By FISH, we identified subregions on chromosome arm 20q that are frequently involved in DNA amplifications in colorectal cancer and that may harbor candidate proto-oncogenes.
No preview · Article · Jul 1999 · Genes Chromosomes and Cancer
[Show abstract][Hide abstract] ABSTRACT: Ovarian cancer is the leading cause of death from gynecological malignancy and the fourth leading cause of cancer death among American women, yet little is known about its molecular aetiology. Studies using comparative genomic hybridization (CGH) have revealed several regions of recurrent, abnormal, DNA sequence copy number that may encode genes involved in the genesis or progression of the disease. One region at 3q26 found to be increased in copy number in approximately 40% of ovarian and others cancers contains PIK3CA, which encodes the p110alpha catalytic subunit of phosphatidylinositol 3-kinase (PI3-kinase). The association between PIK3CA copy number and PI3-kinase activity makes PIK3CA a candidate oncogene because a broad range of cancer-related functions have been associated with PI3-kinase mediated signalling. These include proliferation, glucose transport and catabolism, cell adhesion, apoptosis, RAS signalling and oncogenic transformation. In addition, downstream effectors of PI3-kinase, AKT1 and AKT2, have been found to be amplified or activated in human tumours, including ovarian cancer. We show here that PIK3CA is frequently increased in copy number in ovarian cancers, that the increased copy number is associated with increased PIK3CA transcription, p110alpha protein expression and PI3-kinase activity and that treatment with the PI3-kinase inhibitor LY294002 decreases proliferation and increases apoptosis. Our observations suggest PIK3CA is an oncogene that has an important role in ovarian cancer.
[Show abstract][Hide abstract] ABSTRACT: Using differential display PCR, we have identified a gene [NOEY2, ARHI (designation by the Human Gene Nomenclature Committee)] with high homology to ras and rap that is expressed consistently in normal ovarian and breast epithelial cells but not in ovarian and breast cancers. Reexpression of NOEY2 through transfection suppresses clonogenic growth of breast and ovarian cancer cells. Growth suppression was associated with down-regulation of the cyclin D1 promoter activity and induction of p21(WAF1/CIP1). In an effort to identify mechanisms leading to NOEY2 silencing in cancer, we found that the gene is expressed monoallelically and is imprinted maternally. Loss of heterozygosity of the gene was detected in 41% of ovarian and breast cancers. In most of cancer samples with loss of heterozygosity, the nonimprinted functional allele was deleted. Thus, NOEY2 appears to be a putative imprinted tumor suppressor gene whose function is abrogated in ovarian and breast cancers.
Full-text · Article · Feb 1999 · Proceedings of the National Academy of Sciences
[Show abstract][Hide abstract] ABSTRACT: Genetic linkage, genome mismatch scanning, and analysis of patients with alterations of chromosome 6 have indicated that a major locus for development of the anterior segment of the eye, IRID1, is located at 6p25. Abnormalities of this locus lead to glaucoma. FKHL7 (also called "FREAC3"), a member of the forkhead/winged-helix transcription-factor family, has also been mapped to 6p25. DNA sequencing of FKHL7 in five IRID1 families and 16 sporadic patients with anterior-segment defects revealed three mutations: a 10-bp deletion predicted to cause a frameshift and premature protein truncation prior to the FKHL7 forkhead DNA-binding domain, as well as two missense mutations of conserved amino acids within the FKHL7 forkhead domain. Mf1, the murine homologue of FKHL7, is expressed in the developing brain, skeletal system, and eye, consistent with FKHL7 having a role in ocular development. However, mutational screening and genetic-linkage analyses excluded FKHL7 from underlying the anterior-segment disorders in two IRID1 families with linkage to 6p25. Our findings demonstrate that, although mutations of FKHL7 result in anterior-segment defects and glaucoma in some patients, it is probable that at least one more locus involved in the regulation of eye development is also located at 6p25.
Full-text · Article · Dec 1998 · The American Journal of Human Genetics
[Show abstract][Hide abstract] ABSTRACT: Gene dosage variations occur in many diseases. In cancer, deletions and copy number increases contribute to alterations in the expression of tumour-suppressor genes and oncogenes, respectively. Developmental abnormalities, such as Down, Prader Willi, Angelman and Cri du Chat syndromes, result from gain or loss of one copy of a chromosome or chromosomal region. Thus, detection and mapping of copy number abnormalities provide an approach for associating aberrations with disease phenotype and for localizing critical genes. Comparative genomic hybridization (CGH) was developed for genome-wide analysis of DNA sequence copy number in a single experiment. In CGH, differentially labelled total genomic DNA from a 'test' and a 'reference' cell population are cohybridized to normal metaphase chromosomes, using blocking DNA to suppress signals from repetitive sequences. The resulting ratio of the fluorescence intensities at a location on the 'cytogenetic map', provided by the chromosomes, is approximately proportional to the ratio of the copy numbers of the corresponding DNA sequences in the test and reference genomes. CGH has been broadly applied to human and mouse malignancies. The use of metaphase chromosomes, however, limits detection of events involving small regions (of less than 20 Mb) of the genome, resolution of closely spaced aberrations and linking ratio changes to genomic/genetic markers. Therefore, more laborious locus-by-locus techniques have been required for higher resolution studies. Hybridization to an array of mapped sequences instead of metaphase chromosomes could overcome the limitations of conventional CGH (ref. 6) if adequate performance could be achieved. Copy number would be related to the test/reference fluorescence ratio on the array targets, and genomic resolution could be determined by the map distance between the targets, or by the length of the cloned DNA segments. We describe here our implementation of array CGH. We demonstrate its ability to measure copy number with high precision in the human genome, and to analyse clinical specimens by obtaining new information on chromosome 20 aberrations in breast cancer.
[Show abstract][Hide abstract] ABSTRACT: The centrosomes are thought to maintain genomic stability through the establishment of bipolar spindles during cell division, ensuring equal segregation of replicated chromosomes to two daughter cells. Deregulated duplication and distribution of centrosomes have been implicated in chromosome segregation abnormalities, leading to aneuploidy seen in many cancer cell types. Here, we report that STK15 (also known as BTAK and aurora2), encoding a centrosome-associated kinase, is amplified and overexpressed in multiple human tumour cell types, and is involved in the induction of centrosome duplication-distribution abnormalities and aneuploidy in mammalian cells. STK15 amplification has been previously detected in breast tumour cell lines and in colon tumours; here, we report its amplification in approximately 12% of primary breast tumours, as well as in breast, ovarian, colon, prostate, neuroblastoma and cervical cancer cell lines. Additionally, high expression of STK15 mRNA was detected in tumour cell lines without evidence of gene amplification. Ectopic expression of STK15 in mouse NIH 3T3 cells led to the appearance of abnormal centrosome number (amplification) and transformation in vitro. Finally, overexpression of STK15 in near diploid human breast epithelial cells revealed similar centrosome abnormality, as well as induction of aneuploidy. These findings suggest that STK15 is a critical kinase-encoding gene, whose overexpression leads to centrosome amplification, chromosomal instability and transformation in mammalian cells.
[Show abstract][Hide abstract] ABSTRACT: Amplification is a key mechanism whereby a cancer cell increases the message level of genes that confer a selective advantage when they are overexpressed. In breast cancer, there are many chromosome regions present in multiple copies relative to overall DNA copy number (amplicons), and their target genes are unknown. Using differential display, we have cloned and sequenced the full coding region of a candidate amplicon target gene located on chromosome 13. This candidate is the human homologue of the Caenorhabditis elegans cul-4 gene, cul-4A, a member of the novel cullin gene family, which is involved in cell cycle control of C. elegans. cul-4A was amplified and overexpressed in 3 of 14 breast cancer cell lines analyzed, and it was overexpressed in 8 additional cell lines in which it was not amplified. The latter observation, indicating that its overexpression can occur by mechanisms other than gene amplification, suggests that cul-4A plays a key role in carcinogenesis. Moreover, cul-4A was found to be amplified in 17 of 105 (16%) cases of untreated primary breast cancers, and 14 of 30 cases analyzed (47%) were shown by RNA in situ hybridization to overexpress cul-4A. These results suggest that up-regulation of cul-4A may play an important role in tumor progression.
[Show abstract][Hide abstract] ABSTRACT: We report here the molecular cloning of an approximately 1-Mb region of recurrent amplification at 20q13.2 in breast cancer and other tumors and the delineation of a 260-kb common region of amplification. Analysis of the 1-Mb region produced evidence for five genes, ZNF217, ZNF218, and NABC1, PIC1L (PIC1-like), CYP24, and a pseudogene CRP (Cyclophillin Related Pseudogene). ZNF217 and NABC1 emerged as strong candidate oncogenes and were characterized in detail. NABC1 is predicted to encode a 585-aa protein of unknown function and is overexpressed in most but not all breast cancer cell lines in which it was amplified. ZNF217 is centrally located in the 260-kb common region of amplification, transcribed in multiple normal tissues, and overexpressed in all cell lines and tumors in which it is amplified and in two in which it is not. ZNF217 is predicted to encode alternately spliced, Kruppel-like transcription factors of 1,062 and 1,108 aa, each having a DNA-binding domain (eight C2H2 zinc fingers) and a proline-rich transcription activation domain.
Full-text · Article · Aug 1998 · Proceedings of the National Academy of Sciences
[Show abstract][Hide abstract] ABSTRACT: We have identified three new members of the olfactory receptor (OR) gene family within a large segment of DNA that is duplicated with high similarity near many human telomeres. This segment is present at 3q, 15q, and 19p in each of 45 unrelated humans sampled from various populations. Additional copies are present polymorphically at 11 other subtelomeric locations. The frequency with which the block is present at some locations varies among populations. While humans carry seven to 11 copies of the OR-containing block, it is located in chimpanzee and gorilla predominantly at a single site, which is not orthologous to any of the locations in the human genome. The observation that sequences flanking the OR-containing segment are duplicated on larger and different sets of chromosomes than the OR block itself demonstrates that the segment is part of a much larger, complex patchwork of subtelomeric duplications. The population analyses and structural results suggest the types of processes that have shaped these regions during evolution. From its sequence, one of the OR genes in this duplicated block appears to be potentially functional. Our findings raise the possibility that functional diversity in the OR family is generated in part through duplications and inter-chromosomal rearrangements of the DNA near human telomeres.
Full-text · Article · Feb 1998 · Human Molecular Genetics
[Show abstract][Hide abstract] ABSTRACT: Twenty-one putative chromosome 7-derived expressed sequence tags (ESTs) identified 33 yeast artificial chromosomes (YACs) or P1 clones, which were then used as reagents for physical mapping. FISH mapping established that the ESTs contained within these clones were distributed throughout chromosome 7, with all major cytogenetic bands represented, except 7p13-p15, 7p11, 7q31.2, and 7q35. Each EST sequence identified at least one other sequence in publicly available databases (using search tools such as BLASTN, basic local alignment search tool), and many of the ESTs identified cDNAs and several genomic DNA sequences. However, 7 ESTs did not identify highly significant matches (P < 1 x 10(-5)). Only one (EST01924-D7S2281E) failed to identify any other EST from the dbEST homology searches. BLAST analysis identified at least five genes from EST sequence comparisons: protein tyrosine phosphatase zeta (PTPRZ, also known as RPTPZ) (EST02092), which we had mapped to 7q31.3, in agreement with previous studies; cAMP-dependent protein kinase regulatory subunit bI (EST01644); rat integral membrane glycoprotein (EST00085); human IFNAR gene for interferon alpha/beta receptor (EST00817); and rat 14-3.3 protein gamma subtype (putative protein kinase C regulatory protein) (EST00762). These ESTs will help to develop the map of chromosome 7, which integrates physical, transcriptional, and cytogenetic data, as well as to provide candidate disease genes for chromosome 7-specific disorders.
[Show abstract][Hide abstract] ABSTRACT: Alagille syndrome is an autosomal dominant disorder characterized by abnormal development of liver, heart, skeleton, eye, face and, less frequently, kidney. Analyses of many patients with cytogenetic deletions or rearrangements have mapped the gene to chromosome 20p12, although deletions are found in a relatively small proportion of patients (< 7%). We have mapped the human Jagged1 gene (JAG1), encoding a ligand for the developmentally important Notch transmembrane receptor, to the Alagille syndrome critical region within 20p12. The Notch intercellular signalling pathway has been shown to mediate cell fate decisions during development in invertebrates and vertebrates. We demonstrate four distinct coding mutations in JAG1 from four Alagille syndrome families, providing evidence that it is the causal gene for Alagille syndrome. All four mutations lie within conserved regions of the gene and cause translational frameshifts, resulting in gross alterations of the protein product Patients with cytogenetically detectable deletions including JAG1 have Alagille syndrome, supporting the hypothesis that haploinsufficiency for this gene is one of the mechanisms causing the Alagille syndrome phenotype.
[Show abstract][Hide abstract] ABSTRACT: The >30 known members of the Ets multigene family of transcriptional regulators are increasingly being recognized for their involvement in early embryonic development and late tissue maturation, directing stage-specific and tissue-restricted programs of target gene expression. Identifiable primarily by their 85 amino acid ETS DNA-binding domain and dispersed across all metazoan lineages into distinct subfamilies, Ets genes also produce malignancies in humans and other vertebrates when overexpressed or rearranged into chimeras retaining the ETS domain, suggesting that their oncogenic potential is determined by the program of target genes they regulate. Searching for Ets factors that regulate expression of the HER2/neu (c-erbB2) oncogene in human breast cancer, we identified a new epithelium-restricted Ets encoding an ETS domain homologous to the Drosophila E74/human Elf-1 subfamily, an amino-terminal region (A-region or Pointed domain) homologous to the distantly related Ets-1 subfamily, and a serine-rich box homologous to the transactivating domain of the lymphocyte-restricted High Mobility Group (HMG) protein, SOX4. Recombinant protein encoded by ESX (for epithelial-restricted with serine box) exhibits Ets-like DNA binding specificity in electrophoretic mobility shift assays and, in transient transfection assays, transactivates Ets-responsive promoter elements including that found in the HER2/neu oncogene. ESX is located at chromosome 1q32 in a region known to be amplified in 50% of early breast cancers, is heregulin-inducible and overexpressed in HER2/neu activated breast cancer cells. Tissue hybridization suggests that ESX becomes overexpressed at an early stage of human breast cancer development known as ductal carcinoma in situ (DCIS).
[Show abstract][Hide abstract] ABSTRACT: The helix-loop-helix protein Id-1 regulates growth and differentiation in many mammalian cells. In human fibroblasts, Id1 and Id1', a putative splicing variant, are cell cycle regulated, essential for proliferation, repressed by senescence, and overexpressed by some tumor cells. To better understand Id1, we determined the complete sequence, transcriptional start, and localization of the human Id1 gene. Human Id1 has two exons (426 bp and 42 bp), separated by an intron (239 bp). Id1' results from failure to splice the intron, which encodes 7 amino acids prior to a stop codon. Thus, Id1 and Id1' proteins differ only at the extreme C-terminus. Id1 transcription initiated 96 bp upstream of the initiation AUG; 2 kb of upstream sequence stimulated transcription of a reporter gene. Human Id1 maps to chromosome 20 at q11, very close to the centromere but outside the amplicons frequently found in human cancers.
No preview · Article · Mar 1997 · Biochemical and Biophysical Research Communications
[Show abstract][Hide abstract] ABSTRACT: We report here the complete cDNA sequence, genomic mapping, and immunolocalization of the first human member of the protein kinase C inhibitor (PKCI-1) gene family. The predicted human protein (hPKCI-1) is 96% identical to bovine and 53% identical to maize members, indicating the great evolutionary conservation of this protein family. The hPKCI-1 gene (HGMV-approved symbol PRKCNH1) maps to human chromosome 5q31.2 by fluorescence in situ hybridization. Indirect immunofluorescence shows that hPKCI-1 localizes to cytoskeletal structures in the cytoplasm of a human fibroblast cell line and is largely excluded from the nucleus. The cytoplasmic localization of hPKCI-1 is consistent with a postulated role in mediating a membrane-derived signal in response to ionizing radiation.