Frequent hypomethylation of PTGS2 gene promoter in human term placenta.

BACKGROUND: Gene expression profiles of several tumor suppressor genes are regulated by the methylation and demethylation of their promoters. Here, we aim to identify and quantify the methylation status of four tumor suppressor genes from placentas at term and compare them with the maternal white-blood-cells. METHODS: In order to achieve this objective, DNA enriched from twenty placentas at term and maternal white blood cells was bisulfite-converted and amplified using quantitative real-time methyl-light polymerase chain reaction for the four-genes studied (RASSF1A, APC, RAR-beta, and PTGS2). RESULTS: Among the four genes examined, RASSF1A, APC and RAR-beta promoter regions were hypermethylated in all the placental samples compared with maternal WBCs. Strikingly, PTGS2 was found to be hypomethylated in the placentas compared to the maternal cells. CONCLUSION: Since placental DNA represents fetal methylation profile and it is an established fact that there is certain amount of cell free circulating DNA in human plasma/serum, these data strongly suggest that hypermethylation of RASSF1A, APC and RAR-beta can be used as gender independent biomarkers to distinctly identify placental DNA in maternal blood. In addition, this is the first report which demonstrates hypomethylation of PTGS2 locus which may have important clinical implications e.g. placental abnormalities.

Non-invasive prenatal determination of fetal RhD genotyping from maternal plasma: a preliminary study in Pakistan.

OBJECTIVE: To determine the accuracy of the non-invasive pre-natal real-time polymerase chain reaction based fetal RhD genotyping from maternal plasma. STUDY DESIGN: Cross-sectional study. PLACE AND DURATION OF STUDY: Juma Health Sciences Research Laboratory, The Aga Khan University Hospital, Karachi, from July to December 2008. METHODOLOGY: Cell-free plasma DNA from 21 D-negative women with D-positive spouse between 20-39 weeks of gestation was tested for the presence of exon 5 region of RhD gene using real-time polymerase chain reaction. b-globin was employed as the house-keeping gene. Sensitivity and specificity of the real-time PCR-based non-invasive fetal RhD genotyping was obtained by calculating proportion of the D-positive fetuses that were D-positive at birth as well. RESULTS: Of the 21 D-negative women 13 and 8 neonates were determined to be D-positive and D-negative, respectively, by serologic studies on cord blood samples at birth. RhD status was correctly determined in 17 of 21 cases. There were three false-positive and one false-negative results. The sensitivity and specificity of the assay was 92.3% (95% CI: 62.1, 99.6) and 62.5% (95% CI: 25.9, 89.8), respectively. The positive and negative predictive value of the assay was 80% (95% CI: 51.4, 94.7) and 83.3% (36.5, 99.1), respectively. CONCLUSION: These preliminary results demonstrate the feasibility of non-invasive pre-natal diagnosis of fetal RhD status of D-negative mothers in Pakistan.