Abstract: Objective  To investigate the clinical value of molecular biology in prenatal screening of spinal muscular atrophy(SMA) and its related strategies.
Methods  A total of 4 568 samples of patients that presented to prenatal diagnosis center of our hospital were collected as the research subjects. The denaturing high performance liquid chromate graphy(DHPLC) was used to detect copy number variation of survival motor neuron(SMN1/SMN2), and Sanger sequencing technique was used to detect SMN point mutation.
Results  Of 3 SMA patients in 4 568 samples, there were 2 with homozygous deletion of SMN1 exon 7/8. Both parents were verified as typical SMA carriers, carrying aheterozygous deletion of one copy of SMN1 exon 7/8. Another patient was clinically diagnosed as “type 1+1” SMA patient carrying aheterozygous deletion of one copy of SMN1 exon 7/8, and point mutation site in SMN1 p.Q164X.2. There were 126 SMA carriers, with a carrying rate of approximately 1/36; 84 carriers with one copy of SMN1 exon 7/8; 31 carriers with one copy of SMN1 exon 7, and 11 carriers with one copy of SMN1 exon 8.3. On the basis of identifying the SMA proband and carrier genotype, we performed SMA prenatal diagnosis of amniotic fluid puncture on both 25 couples who were carriers at 18 weeks of pregnancy, including 3 fetus carrying a homozygous deletion of SMN1 exon 7/8(SMA patient), and 1 fetus carrying aheterozygous deletion of SMN1 exon 7/8(SMA carrier). There was no abnormal SMN1 copy number in the remaining fetuses. Sanger sequencing 1 fetal carrying p.Q164x point mutation site, while the remaining samples had no abnormal SMN copy number.
Conclusion  DHPLC combined point mutation sequencing was used to detect the pathogenesis of SMA, which fully confirmed their significant value in the detection of genetic diseases such as SMA. The newly reported SMN mutation site of pathogenic gene p.Q164X enriched the database of SMA pathogenic genes in Chinese population. Carrier screening for single-gene disorder is the basis of prenatal diagnosis, which can identify the types of variant and possible pathogenic sites in carriers, select accurate molecular means for targeted prenatal diagnosis of fetal disease, reduce the family and social economic burden as well as the psychological burden of patients and their families.

Key words: denaturing high performance liquid chromatography, Sanger sequencing, spinal muscular atrophy, prenatal diagnosis, SMN1