RPS6KA4/MIR1237 and AURKC promoter regions are differentially methylated in Wilms' tumor.

Wilms' tumor (WT) is the most frequent renal cancer in childhood, the occurrence of which is characterized by a relatively low frequency of associated mutations. While epigenetic alterations have been postulated to play a relevant role in the emergence of this tumor, the mechanisms involved in WT development remain largely unknown. In this study, the DNA methylation profile of WT was characterized with Beadchip array. Comparisons between WT with normal kidney identified 827 differentially methylated regions, most of which were attributable in hypermethylation in CpG islands. Among affected genes, WT1 and TP73 showed altered enhancers where hypermethylation was validaded by pyrosequencing. Thirty differentially methylated regions (DMRs) were identified in WT as compared to normal kidney, two of which were previously described. Two novel DMRs, located in RPS6KA4/MIR1237 and the AURKC promoter, were found to be hypermethylated in WT. Altogether, our data reinforced the relevance of alterations of DNA methylation in WT, highlighting the complex nature of these alterations that affect promoter regions as well as enhancers, UTRs and gene bodies.

Detailed analysis of X chromosome inactivation in a 49,XXXXX pentasomy.

BACKGROUND: Pentasomy X (49,XXXXX) has been associated with a severe clinical condition, presumably resulting from failure or disruption of X chromosome inactivation. Here we report that some human X chromosomes from a patient with 49,XXXXX pentasomy were functionally active following isolation in inter-specific (human-rodent) cell hybrids. A comparison with cytogenetic and molecular findings provided evidence that more than one active X chromosome was likely to be present in the cells of this patient, accounting for her abnormal phenotype. RESULTS: 5-bromodeoxyuridine (BrdU)-pulsed cultures showed different patterns among late replicating X chromosomes suggesting that their replication was asynchronic and likely to result in irregular inactivation. Genotyping of the proband and her mother identified four maternal and one paternal X chromosomes in the proband. It also identified the paternal X chromosome haplotype (P), indicating that origin of this X pentasomy resulted from two maternal, meiotic non-disjunctions. Analysis of the HUMANDREC region of the androgen receptor (AR) gene in the patient's mother showed a skewed inactivation pattern, while a similar analysis in the proband showed an active paternal X chromosome and preferentially inactivated X chromosomes carrying the 173 AR allele. Analyses of 33 cell hybrid cell lines selected in medium containing hypoxanthine, aminopterin and thymidine (HAT) allowed for the identification of three maternal X haplotypes (M1, M2 and MR) and showed that X chromosomes with the M1, M2 and P haplotypes were functionally active. In 27 cell hybrids in which more than one X haplotype were detected, analysis of X inactivation patterns provided evidence of preferential inactivation. CONCLUSION: Our findings indicated that 12% of X chromosomes with the M1 haplotype, 43.5% of X chromosomes with the M2 haplotype, and 100% of the paternal X chromosome (with the P haplotype) were likely to be functionally active in the proband's cells, a finding indicating that disruption of X inactivation was associated to her severe phenotype.