Background Trisomy 21 is the most common chromosomal aberration in live births. Some efforts have been made to develop noninvasive prenatal detection of trisomy 21 by using fetal DNA in maternal plasma. Due to the maternal DNA background, a distinguishable marker between maternal DNA and fetal DNA must be used, such as DNA methylation. The objective of this study was to search for fetal-specific methylation markers on chromosome 21. Methods We chose six genes highly or specifically expressed in placenta and screened the methylation status of these gene promoter regions by combination of methylated-DNA precipitation and methylation-sensitive restriction enzymes assay (COMPARE-MS). We further determined the methylation status of each CpG site within selected gene fragments by bisulfite sequencing. At last, we detected the placenta-derived methylation marker in the first-trimester maternal plasma by real-time methylation-specific PCR (MSP). Results Down syndrome (DS) critical region gene 4 (DSCR4) promoter region was found to be hypomethylated in placental tissues and densely methylated in maternal blood cells. Unmethylated DSCR4 (Down syndrome) sequence can be detected in the first-trimester maternal plasma. Conclusion DSCR4 promoter DNA is a candidate fetal epigenetic marker for noninvasive prenatal detection of trisomy 21. Copyright  2011 John Wiley & Sons, Ltd.

Background: miRNAs are a group of small RNA molecules regulating target genes by inducing mRNA degradation or translational repression. Aberrant expression of miRNAs correlates with various cancers. Although miR-135a has been implicated in several other cancers, its role in breast cancer is unknown. HOXA10 however, is associated with multiple cancer types and was recently shown to induce p53 expression in breast cancer cells and reduce their invasive ability. Because HOXA10 is a confirmed miR-135a target in more than one tissue, we examined miR-135a levels in relation to breast cancer phenotypes to determine if miR-135a plays role in this cancer type. Methods: Expression levels of miR-135a in tissues and cells were determined by poly (A)-RT PCR. The effect of miR-135a on proliferation was evaluated by CCK8 assay, cell migration and invasion were evaluated by transwell migration and invasion assays, and target protein expression was determined by western blotting. GFP and luciferase reporter plasmids were constructed to confirm the action of miR-135a on downstream target genes including HOXA10. Results are reported as means ± S.D. and differences were tested for significance using 2-sided Student\"s t-test. Results: Here we report that miR-135a was highly expressed in metastatic breast tumors. We found that the expression of miR-135a was required for the migration and invasion of breast cancer cells, but not their proliferation. HOXA10, which encodes a transcription factor required for embryonic development and is a metastasis suppressor in breast cancer, was shown to be a direct target of miR-135a in breast cancer cells. Our analysis showed that miR-135a suppressed the expression of HOXA10 both at the mRNA and protein level, and its ability to promote cellular migration and invasion was partially reversed by overexpression of HOXA10. Conclusions: In summary, our results indicate that miR-135a is an onco-miRNA that can promote breast cancer cell migration and invasion. HOXA10 is a target gene for miR-135a in breast cancer cells and overexpression of HOXA10 can partially reverse the miR-135a invasive phenotype.

miRNAs are a family of approximately 22-nuleotide-long noncoding RNAs involved in the formation and progress of tumors. Since traditional methods for the detection of miRNAs expression have many disadvantages, we developed a simple method called polyA RT PCR. With this method, we detected a series of miRNAs and found that mir-126 is one of the miRNAs underexpressed in breast cancer cells. Flow cytometry analysis showed that mir-126 inhibited cell cycle progression from G1/G0 to S. Further studies revealed that mir-126 targeted IRS-1 at the translation level. Knocking down of IRS-1 suppresses cell growth in HEK293 and breast cancer cell MCF-7, which recapitulates the effects of mir-126. In conclusion, we developed a simple method for high-throughput screening of miRNAs and found that mir-126, a cell growth suppressor, targets IRS-1.