Detection of paternal alleles in maternal plasma for non-invasive prenatal diagnosis of β-thalassemia: A feasibility study in southern Chinese

To evaluate in maternal plasma, the efficacy of detecting the paternal beta-gene mutation and informative single nucleotide polymorphisms (SNPs) linked to the paternal-mutant or -normal allele in non-invasive prenatal diagnosis (NIPND).In 20 at-risk pregnancies, using the allele-specific arrayed primer extension (AS-APEX) technology of the previously published "Thalassemia" array, cyanine-5-deoxycytosine triphosphate (Cy5-dCTP) was incorporated into the extended strands to matched PCR-amplified maternal plasma DNA templates, to detect both the paternal beta-gene mutation and informative paternal SNPs.Sensitivity experiment showed that 5pg DNA as starting template gave detectable signals on the array. In 13 cases (65%), the paternal-derived beta-gene mutation and/or informative mutant-associated SNP were detected. A subsequent invasive procedure was required to determine if the fetus had a beta-thalassemia (thal) major or minor genotype. In 3 cases (15%), absence of the paternal mutant or mutant-associated SNP excluded a beta-thal major fetus; while in 4 cases (20%), this approach was non-discriminative as both parents carry the same mutation without any informative SNP.This approach was useful in 16 out of 20 (80%) pregnancies at risk for beta-thal in southern Chinese.