RESUMO
Allele losses from chromosome 17 are common in sporadic ovarian tumors. Previously, we reported high rates of LOH (up to 70%) from 17q25 at the marker THH59 in a bank of malignant ovarian tumors. We have extended this study to 70 tumors with 17 markers from the long arm of chromosome 17. In most cases, the data are consistent with whole chromosome loss, but we have identified a minimal region of deletion that is centered around 4 microsatellites with zero recombination at map position 106.9 cM. A P1/BAC contig across the region (approximately 200 kb) was constructed and used to determine the precise position and order of the microsatellites. The contig was shown to hybridize to 17q25 by fluorescence in situ hybridization analysis. The DNA sequence of the entire contig was determined and analyzed by BLAST searches. A 4-kb cDNA was subsequently identified with homology to the yeast, Drosophila and mammalian septin family of genes. We have designated this gene Ovarian/Breast (Ov/Br) septin. Two splice variants were demonstrated within the 200-kb contig, which differ only at exon 1. Within the contig, approximately 45% of the septin alpha transcript was identified and 38% of the septin beta transcript. The septins are a family of genes involved in cytokinesis and cell cycle control. Their known functions are consistent with the hypothesis that the human 17q25 septin gene is a candidate for the ovarian tumor suppressor gene.
Assuntos
Cromossomos Humanos Par 17 , GTP Fosfo-Hidrolases , Proteínas de Ligação ao GTP/genética , Genes Supressores de Tumor , Neoplasias Ovarianas/genética , Sequência de Aminoácidos , Deleção Cromossômica , Mapeamento Cromossômico , Mapeamento de Sequências Contíguas , Análise Mutacional de DNA , DNA Complementar/genética , DNA Complementar/isolamento & purificação , DNA de Neoplasias/genética , DNA de Neoplasias/isolamento & purificação , Feminino , Humanos , Perda de Heterozigosidade , Dados de Sequência Molecular , Septinas , Homologia de Sequência de AminoácidosRESUMO
We have determined the methylation status of the CpG island of the oestrogen receptor alpha gene in seven human ovarian cell lines. Cell lines expressing oestrogen receptor alpha showed no evidence of hypermethylation. In three of four cell lines that produced no detectable oestrogen receptor alpha protein, hypermethylation was observed at the NotI site of the CpG island. These results indicate that aberrant hypermethylation may be responsible for a significant proportion of epithelial ovarian tumours in which oestrogen receptor alpha expression is lost.