ABSTRACT
AIM: Methylated DNA immunoprecipitation real-time quantitative polymerase chain reaction (MeDIP-real-time qPCR) has been introduced as noninvasive prenatal test that has shown absolute detection rate in the screening of Down syndrome. Herein, we aimed to propose a novel modification of MeDIP-qPCR and assess its potential to alleviate the overall cost of the test, being used in very early weeks of pregnancy, and develop it to a noninvasive prenatal diagnosis biosensor in future researches. METHODS: Cell-free fetal DNA (cffDNA) isolated from 60 pregnant women, including 29 normal and 31 trisomy 21 pregnancies, were analyzed using proposed MeDIP protocol. Enriched methylated DNA sequences were amplified through real-time qPCR using eight fetal-specific primer pairs. The status of samples was determined through the calculation of D-value with the cutoff point of zero. RESULTS: The sensitivity and specificity of the MeDIP protocols using nanoparticles were 100% and 100%, respectively. CONCLUSION: Remarkable decrease in the price of MeDIP test per each patient would be a reasonable factor to confirm it on larger sample size. Moreover, the high detection rate of screening and the availability of the required instruments around the world make satisfactory reasons to be tested in earlier weeks of pregnancy, thanks to the high sensitivity of gold shell nanoparticles.
Subject(s)
DNA Methylation , Down Syndrome/blood , Down Syndrome/diagnosis , Immunoprecipitation/methods , Prenatal Diagnosis/methods , Real-Time Polymerase Chain Reaction/methods , Adult , Clinical Protocols , Female , Humans , Immunoprecipitation/standards , Pregnancy , Real-Time Polymerase Chain Reaction/standards , Sensitivity and SpecificityABSTRACT
Objective: Recent advances in non-invasive prenatal diagnosis (NIPD) through cell free fetal DNA (cffDNA) has highlighted cffDNA purification as a critical initial step. Herein, we aimed to compare the efficiency of one proposed protocol with two commercial kits for isolation of cffDNA. Materials and methods: cffDNA was isolated from whole blood of 50 normal pregnancies using one proposed manual protocol compared with QIAamp DNA Blood Mini and Bioneer Kits. Methylated DNA immunoprecipitation real time polymerase chain reaction (MeDIP-Real time PCR) was performed to quantify three fetal specific sequences. Results: Maximum cffDNA quantity was obtained by suggested protocol (248.79 ± 14.07 ng/µl) and the best quality was achieved by Bioneer Kit (OD ratio: 260/280 nm/nm: 1.69 ± 0.09, 260/230 nm/nm: 1.15 ± 0.13) (p < 0.001). Enrichment of fetal specific sequences was significantly higher when proposed protocol was used to isolate cffDNA (p = 0.01). Conclusion: Inhibitory effect of NaI on nucleases and double digestion of DNA associated proteins may be the main reasons behind the superiority of suggested protocol. Significantly higher amplification of fetal specific sequences in suggested protocol would be a strong evidence on recovery of small fetal fragments as demonstrated with its maximum total DNA quantity and amplification in different PCR reactions.
