Supplementary value of denaturing high performance liquid chromatography for routine prenatal diagnosis of spinal muscular atrophy by multiple ligation-dependent probe amplification

Abstract

To explore the feasibility of high performance liquid chromatography (DHPLC) combined with multiple ligation-dependent probe amplification (MLPA) for the prenatal diagnosis of spinal muscular atrophy (SMA). Three families who had given birth to children with SMA type I were subjected to prenatal diagnosis. Peripheral blood samples were collected from the three couples, and 10 mL amniotic fluid was taken for each fetus through amniocentesis at 16-24 gestational week. Following DNA extraction, maternal contamination was excluded by STR analysis. Copy numbers of the SMN genes were detected by denaturing high performance liquid chromatography (DHPLC). Relative copy number of SMN1, SMN2 and reference genes was detected with a MLPA P021 assay kit. The three couples were all found to harbor heterozygous deletion of exon 7 of the SMN1 gene by DHPLC. MLPA analysis also suggested that the three couples were all carriers of SMA mutations. The fetus of family 1 harbored homozygous deletion of exons 7 and 8 of the SMN1 gene, in addition with heterozygous deletion of exons 7 and 8 of the SMN2 gene, suggesting that the fetus had SMA. The fetus of family 2 also harbored homozygous deletion of exons 7 and 8 of the SMN1 gene, while the copy number of SMN2 gene was normal, suggesting that the fetus was a SMA patient too. The fetus of family 3 harbored heterozygous deletion of exons 7 and 8 of the SMN1 gene, in addition with heterozygous deletion of exons 7 and 8 of the SMN2 gene, suggesting that the fetus was a carrier. DHPLC can effectively screen carriers of SMA mutations. Combined DHPLC and MLPA can provide accurate diagnosis for fetuses with a high risk for SMA.