The use of cell-free fetal DNA in maternal plasma for noninvasive prenatal linkage analysis in beta globin gene cluster.

OBJECTIVES

To use the PCR-RFLP-based linkage analysis for non-invasive prenatal diagnosis of β-thalassemia.

BACKGROUNDS: Thalassemia is a prevalent genetic disorder occurring throughout the world. Cell-free fetal DNA (cffDNA) in the maternal plasma during pregnancy has been used to develop non-invasive prenatal screening and diagnostic tests.

METHODS

PCR-RFLP for six SNPs in the β-globin gene was executed on paternal and maternal DNA as well as DNA extracted from CVS of the fetuses in seven β-thalassemic families. Based on the results, two families in which the paternal inherited SNPs in specific loci were different from the maternal one were selected and PCR-RFLP was performed on cffDNA extracted from the maternal plasma.

RESULTS

Paternal SNPs in cffDNA were distinguished and the inheritance of paternally normal or mutant β globin allele was predicted by linkage analysis.

CONCLUSION

The use of PCR-RFLP on cffDNA as a simple and inexpensive method was capable to provide similar results achieved by studying CVS of the fetuses. However, there is a limiting factor in this approach, namely that there is the little amount of cffDNA in maternal plasma. The PCR yield was improved either by adding BSA to PCR reaction or increasing the PCR cycles (Tab. 2, Fig. 2, Ref. 18).