Studies on the prenatal diagnosis of spinal muscular atrophy by multiplex ligation⁃dependent probe amplification

Objective To investigate the value of multiplex ligation⁃dependent probe amplification (MLPA) method in the prenatal diagnosis of spinal muscular atrophy (SMA). Methods Six SMA pedigrees, which included 7 patients, 12 parents and 6 fetuses, were admitted in our hospital. MLPA was used to detect the survival motor neuron (SMN) and other modifier genes, according to steps of hybridization, ligation, PCR reaction, fragment separation by capillary electrophoresis and peak pattern evaluation. Synchronously, the deletion of SMN1 gene was detected by polymerase chain reaction⁃restriction fragment length polymorphism (PCR⁃RFLP). The DNA samples of fetuses were collected by centrifuging the amniotic fluid as well as derived from amniotic cell culture. Results According to MLPA, 7 patients and 1 fetus were detected to carry homozygous deletion of survival motor neuron 1 (SMN1) gene, which was also detected by PCR⁃PFLP. In addition, 11 parents and 5 fetuses carried one copy of SMN1 gene, while 1 parent who was also a carrier of SMA carried two copies of SMN1 gene. Furthermore, after being analyzed by MLPA, 10 cases carried one copy of SMN2 gene, while 15 cases had two copies of SMN2 gene. After detecting the neuronal apoptosis inhibitory protein (NAIP) gene, 3 cases had the deletion of NAIP gene while others showed normal. Conclusion MLPA can detect the deletion and quantify the copy numbers of SMN and other modifier genes, improving the efficiency and stability of genetic diagnosis. It is adequate for detecting patients and carriers of SMA, as well as providing reliable evidence for genetic counseling. DOI：10.3969/j.issn.1672⁃6731.2012.03.012