SMN1 gene deletion analysis using mid-trimester amniotic fluid cells by real-time PCR

Abstract

Objectives To investigate the prenatal diagnosis method of spinal muscular atrophy with amniotic fluid sample. Methods Totally 1 064 amniotic fluid samples from mid-trimester pregnant women were enrolled during January 2015 and January 2016 in 4 hospitals. Genetic analysis was performed for detecting potential contamination of maternal tissue by a genetic technique based on short tandem repeat (STR) markers. Deletion of SMN1 gene was detected in 1 062 uncontaminated amniotic fluid samples by real-time PCR and multiplex ligation-dependent probe amplification (MLPA) respectively. Results Two contaminated amniotic fluid samples were detected within 1 064 mid-trimester pregnant women by STR genotyping. The other 1 062 uncontaminated amniotic fluid samples were tested by real-time PCR. There were 37 samples with heterozygous deletion of Exon 7 of SMN1 gene (3.67%), 34 samples with heterozygous deletion of Exon 8 of SMN1 gene (3.2%) and two samples with homozygous deletion of Exon7 and Exon8 of SMN1 gene (0.19%) respectively, while other samples observed with no deletion of Exon7 and Exon8 in SMN1 gene. Totally 41 samples with heterozygous or homozygous deletion of SMN1 gene and 55 samples with undetected deletion of SMN1 gene were confirmed by MLPA and the results showed 100% consistence with that of real-time PCR. Conclusions Both real-time PCR and MLPA are suitable for detecting the deletion of SMN1 gene with amniotic fluid sample. Real-time PCR exhibits less sample requirement and time compared with MLPA.(Chin J Lab Med, 2016, 39: 418-422) Key words: Muscular atrophy, spinal; Amniotic fluid; Survival of motor neuron 1 protein; Gene deletion; Real-time polymerase chain reaction; Multiplex polymerase chain reaction