Conserved mechanism of PLAG1 activation in salivary gland tumors with and without chromosome 8q12 abnormalities: identification of SII as a new fusion partner gene.
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We have previously shown (K. Kas et al, Nat. Genet., 15: 170-174, 1997) that the developmentally regulated zinc finger gene pleomorphic adenoma gene 1 (PLAG1) is the target gene in 8q12 in pleomorphic adenomas of the salivary glands with t(3;8)(p21;q12) translocations. The t(3;8) results in promoter swapping between PLAG1 and the constitutively expressed gene for beta-catenin (CTNNB1), leading to activation of PLAG1 expression and reduced expression of CTNNB1. Here we have studied the expression of PLAG1 by Northern blot analysis in 47 primary benign and malignant human tumors with or without cytogenetic abnormalities of 8q12. Overexpression of PLAG1 was found in 23 tumors (49%). Thirteen of 17 pleomorphic adenomas with a normal karyotype and 5 of 10 with 12q13-15 abnormalities overexpressed PLAG1, which demonstrates that PLAG1 activation is a frequent event in adenomas irrespective of karyotype. In contrast, PLAG1 was overexpressed in only 2 of 11 malignant salivary gland tumors analyzed, which suggests that, at least in salivary gland tumors, PLAG1 activation preferentially occurs in benign tumors. PLAG1 over-expression was also found in three of nine mesenchymal tumors, i.e., in two uterine leiomyomas and one leiomyosarcoma. RNase protection, rapid amplification of 5'-cDNA ends (5'-RACE), and reverse transcription-PCR analyses of five adenomas with a normal karyotype revealed fusion transcripts in three tumors. Nucleotide sequence analysis of these showed that they contained fusions between PLAG1 and CTNNB1 (one case) or PLAG1 and a novel fusion partner gene, i.e., the gene encoding the transcription elongation factor SII (two cases). The fusions occurred in the 5' noncoding region of PLAG1, leading to exchange of regulatory control elements and, as a consequence, activation of PLAG1 gene expression. Because all of the cases had grossly normal karyotypes, the rearrangements must result from cryptic rearrangements. The results suggest that in addition to chromosomal translocations and cryptic rearrangements, PLAG1 may also be activated by mutations or indirect mechanisms. Our findings establish a conserved mechanism of PLAG1 activation in salivary gland tumors with and without 8q12 aberrations, which indicates that such activation is a frequent event in these tumors. (+info)
Identification of a human HECT family protein with homology to the Drosophila tumor suppressor gene hyperplastic discs.
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Use of the differential display technique to isolate progestin-regulated genes in T-47D human breast cancer cells led to identification of a novel gene, EDD. The cDNA sequence contains a 2799 amino acid open reading frame sharing 40% identity with the predicted 2894 amino acid product of the Drosophila melanogaster tumor suppressor gene hyperplastic discs, while the carboxy-terminal 889 amino acids show 96% identity to a rat 100 kDa HECT domain protein. EDD mRNA was progestin-induced in T-47D cells and was highly abundant in testes and expressed at moderately high levels in other tissues, suggesting a broad role for EDD. Anti-EDD antibodies immunoprecipitated an approximately 300 kDa protein from T-47D cell lysates. HECT family proteins function as E3 ubiquitin-protein ligases, targeting specific proteins for ubiquitin-mediated proteolysis. EDD is likely to function as an E3 as in vitro translated protein bound ubiquitin reversibly through a conserved HECT domain cysteine residue. EDD was localized by FISH to chromosome 8q22, a locus disrupted in a variety of cancers. Given the homology between EDD and the hyperplastic discs protein, which is required for control of imaginal disc growth in Drosophila, EDD potentially has a role in regulation of cell proliferation or differentiation. (+info)
Angiopoietins 3 and 4: diverging gene counterparts in mice and humans.
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The angiopoietins have recently joined the members of the vascular endothelial growth factor family as the only known growth factors largely specific for vascular endothelium. The angiopoietins include a naturally occurring agonist, angiopoietin-1, as well as a naturally occurring antagonist, angiopoietin-2, both of which act by means of the Tie2 receptor. We now report our attempts to use homology-based cloning approaches to identify new members of the angiopoietin family. These efforts have led to the identification of two new angiopoietins, angiopoietin-3 in mouse and angiopoietin-4 in human; we have also identified several more distantly related sequences that do not seem to be true angiopoietins, in that they do not bind to the Tie receptors. Although angiopoietin-3 and angiopoietin-4 are strikingly more structurally diverged from each other than are the mouse and human versions of angiopoietin-1 and angiopoietin-2, they appear to represent the mouse and human counterparts of the same gene locus, as revealed in our chromosomal localization studies of all of the angiopoietins in mouse and human. The structural divergence of angiopoietin-3 and angiopoietin-4 appears to underlie diverging functions of these counterparts. Angiopoietin-3 and angiopoietin-4 have very different distributions in their respective species, and angiopoietin-3 appears to act as an antagonist, whereas angiopoietin-4 appears to function as an agonist. (+info)
An ankyrin-like protein with transmembrane domains is specifically lost after oncogenic transformation of human fibroblasts.
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We have identified a novel transformation-sensitive mRNA, which is present in cultured fibroblasts but is lacking in SV40 transformed cells as well as in many mesenchymal tumor cell lines. The corresponding gene is located on human chromosome 8 in band 8q13. The open reading frame of the mRNA encodes a protein of 1119 amino acids forming two distinct domains. The N-terminal domain consists of 18 repeats that are related to the cytoskeletal protein ankyrin. The C-terminal domain contains six putative transmembrane segments that resemble many ion channels. This overall structure is reminiscent of TRP-like proteins that function as store-operated calcium channels. The novel protein with an Mr of 130 kDa is expressed at a very low level in human fibroblasts and at a moderate level in liposarcoma cells. Overexpression in eukaryotic cells appears to interfere with normal growth, suggesting that it might play a direct or indirect role in signal transduction and growth control. (+info)
Human NDUFB9 gene: genomic organization and a possible candidate gene associated with deafness disorder mapped to chromosome 8q13.
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Human NADH dehydrogenase (ubiquinone) 1beta-subcomplex, 9 (NDUFB9) is a nuclear encoded mitochondrial protein with the respiratory electron transport chain. It has been physically mapped to a 1-Mb deletion at chromosome 8q13 which also contains the gene for branchio-oto-renal (BOR) syndrome. BOR syndrome is characterized by branchial and renal abnormalities with hearing impairment. Since several hereditary deafness disorders have been associated with mitochondrial mutations, NDUFB9 was considered a candidate gene for BOR syndrome. Recently, EYA1 gene has been identified in the region which underlies the BOR syndrome but majority of BOR families did not show mutations in the EYA1 gene. Here we have determined the genomic structure of the NDUFB9 gene, including the nucleotide sequence, organization and the boundaries of the four coding exons. PCR primers were designed from the adjacent intron sequences that allow amplification of the four exons that encode the complete open reading frame. To identify whether mutations in NDUFB9 are involved in causing the BOR syndrome, we screened 9 BOR families which did not show mutations in the EYA1 gene by heteroduplex analysis; however, no mutations were found. (+info)
Trisomies 8 and 20 characterize a subgroup of benign fibrous lesions arising in both soft tissue and bone.
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Trisomy 8 and trisomy 20 are nonrandom aberrations in desmoid tumors. The presence of these trisomies in related benign fibrous lesions of bone has not been previously addressed. In this study, 22 specimens from 19 patients diagnosed with desmoid tumor, desmoplastic fibroma, periosteal desmoid tumor, osteofibrous dysplasia, or fibrous dysplasia were examined by cytogenetic analysis of short-term cultures and bi-color fluorescence in situ hybridization of cytological touch preparations or paraffin-embedded tissue with centromeric probes for chromosomes 8 and 20. Trisomy 8 and trisomy 20 were detected by molecular cytogenetic methodologies in 15 specimens, including 10 primary bone lesions. Traditional cytogenetic analysis revealed trisomy 8 in two cases of osteofibrous dysplasia. Our findings demonstrate that trisomy 8 and trisomy 20 are also nonrandom aberrations in histologically similar, but clinically distinct, benign fibrous lesions of bone. (+info)
Differential expression assay of chromosome arm 8p genes identifies Frizzled-related (FRP1/FRZB) and Fibroblast Growth Factor Receptor 1 (FGFR1) as candidate breast cancer genes.
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Deletions and amplifications are frequent alterations of the short arm of chromosome 8 associated with various types of cancers, including breast cancers. This indicates the likely presence of tumor suppressor genes and oncogenes. In the present study, we have used the expressed sequence tag (EST) map of 8p11-21 to assemble a set of available cDNAs representing genes from this region. DNA arrays were prepared for expression analysis and search for genes potentially involved in breast cancer. Underexpresion in tumoral breast cells (versus normal breast) was observed for 15 transcripts. Among these, the Frizzled-related gene FRP1/FRZB, was turned off in 78% of breast carcinomas, suggesting that the lack of its product may be associated with malignant transformation. Overexpression in tumoral breast cells was observed for 13 genes. The FGFR1 gene, that encodes a tyrosine kinase receptor for members of the fibroblast growth factor family, was identified as a good candidate for one amplification unit. Taken together, our results demonstrate that such a strategy can rapidly identify genes with an altered pattern of expression and provide candidate genes for malignancies. (+info)
Delineation of the critical deletion region for congenital heart defects, on chromosome 8p23.1.
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Deletions in the distal region of chromosome 8p (del8p) are associated with congenital heart malformations. Other major manifestations include microcephaly, intrauterine growth retardation, mental retardation, and a characteristic hyperactive, impulsive behavior. We studied genotype-phenotype correlations in nine unrelated patients with a de novo del8p, by using the combination of classic cytogenetics, FISH, and the analysis of polymorphic DNA markers. With the exception of one large terminal deletion, all deletions were interstitial. In five patients, a commonly deleted region of approximately 6 Mb was present, with breakpoints clustering in the same regions. One patient without a heart defect or microcephaly but with mild mental retardation and characteristic behavior had a smaller deletion within this commonly deleted region. Two patients without a heart defect had a more proximal interstitial deletion that did not overlap with the commonly deleted region. Taken together, these data allowed us to define the critical deletion regions for the major features of a del8p. (+info)