Women with balanced X-autosome translocations constitute a heterogeneous group of patients whose most frequent phenotypic alteration is premature ovarian failure. Since the long arm of chromosome X (Xq) is a critical region for ovarian function, it has been postulated that this phenotype might result from either the disruption of genes responsible for ovarian development or from epigenetic modifications of complete genes present in the region involved in the translocation, as a consequence of a chromosomal position effect. Alterations in the expression of genes located on the Xq and/or autosome involved in the rearrangement could occur by spatial reorganization of the chromatin and consequent interference with the interactions of the regulatory regions of the Xq and/or autosome, essential for the adequate transcription of the genes responsible for the ovarian function. Thus, the present research project proposes an investigation of women with X-autosome translocations regarding the reorganization of chromatin, its effect on the complex regulation of gene expression and its implications in ovarian function.The characterization of the chromosome rearrangements and the identification of possible genomic imbalances will be performed by using classical cytogenetic techniques and total genomic array assays. The chromosome microdissection technique will be used for the derivative chromosomes involved in the translocations, followed by PCR amplification of these chromosomes and genomic array analysis, for a precise determination of the breakpoints in the rearrangements and the integrity of the genes located in those regions. Alterations in the gene expression pattern will be identified by means of the expression array technique. In addition, we will investigate the nuclear positioning of the genes with altered expression in the women with an X-autosome translocation in relation to the chromosomal territory of the X chromosome, using the fluorescence in situ hybridization (FISH) technique with whole-chromosome paint probes and single-sequence probes cloned in bacterial artificial chromosomes (BACs), specific for genes with altered expression which are related with the ovarian function.The results of this study will allow a better understanding of the complex regulation mechanism of X-chromosome gene transcription related to the nuclear architecture and possibly the identification of genes related with premature ovarian failure.
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