Recent research on the treatment of spinal muscular atrophy / 中国当代儿科杂志

Spinal muscular atrophy (SMA) is an autosomal recessive neuromuscular disease characterized by progressive muscular weakness and atrophy. SMA, as an inherited disease, is the leading cause of death in infants and young children. Rapid progress has been made in the research field of SMA in recent years, and some related treatment drugs have been successfully approved for marketing. This article reviews the recent research advances in the treatment of SMA.

Investigation and analysis of genetic testing in a SMA cohort based on the national rare diseases registry system of China / 中华检验医学杂志

Objective:To explore application status and development trend of spinal muscular atrophy (SMA) genetic diagnosis technology based on the national rare diseases registry system of China.Method:A total of 200 SMA children registered at the Capital Institute of Pediatrics from July 2016 to December 2018 were included in this retrospective cross-sectional survey. The basic data, clinical subtypes, genotypes, and related genetic testing information of SMA children were obtained by checking SMA registration information, genetic testing reports, and also by telephone follow-up. The patient number and the composition of different genetic diagnosis technologies were analyzed by the stratification of genetic testing at various time. The correlation between the proportion of genetic diagnosis technology and genetic testing time was analyzed with Pearson correlation analysis.Result:There were 3 SMA cases with incomplete data, the remaining 197 SMA cases were included in this study. There were 37 (18.8%), 115 (58.4%) and 45 (22.8%) patients with type Ⅰ, Ⅱ and Ⅲ SMA, respectively. There were 185 cases of SMN1 homozygous deletion (93.9%), and 12 cases with compound heterozygotes (6.1%). Seven SMA-related genetic technologies were used from 2004 to 2017. MLPA accounted for 54.1% (100/185) used approach, followed by PCR-RFLP and first-generation sequencing, which accounted for 22.7% (42/185) and 10.3% (19/185), respectively. Nine, 6, 5 and 4 cases were tested with AS-PCR, qPCR, WES and DHPLC, respectively (2.2%-4.9%). The proportion of MLPA increased gradually since 2010 ( r=0.95, P<0.05), while PCR-RFLP declined gradually since 2004 ( r=-0.99, P<0.05). No correlation was found between technology and testing time for other genetic testing technologies ( P>0.05). The proportion of quantitative genetic technologies (MLPA, qPCR and DHPLC) increased gradually since 2010 ( r=0.94, P<0.05), and qualitative genetic technologies (PCR-RFLP, first-generation sequencing, AS-PCR and WES) decreased gradually since 2004 ( r=-0.94, P<0.05). The duplication detection rates of homozygous deletion and compound heterozygous mutation were 12.4% (23/185) and 41.7% (5/12), respectively (χ 2=5.86, P<0.05). During 2008-2015, the proportion of "the reports of both copy numbers of SMN1 gene and SMN2 gene" increased from 56.8% (21/37) in 2008-2015 to 69.1% (56/81) in 2016-2017. Conclusion:Genetic diagnosis of SMA has gradually developed from qualitative detection technology to quantitative detection technology, such as MLPA and qPCR, in China. In more and more SMA quantitative test reports, quantitative results of SMN2 gene are also provided in addition to quantitative results of SMN1 gene.

Determination of SMN1 and SMN2 Copy Numbers in a Korean Population using Multiplex Ligation-dependent Probe Amplification / 대한진단검사의학회지

Determination of the copy number of the survival motor neuron (SMN) gene is important for detecting spinal muscular atrophy (SMA) carriers and compound heterozygous patients. Multiplex ligationdependent probe amplification (MLPA) assay is a simple and efficient technique used for detecting variations in the copy numbers of different genes. Race- and ethnicity-based variation in the SMA carrier frequency and the '2+0' genotype of SMN1 are important factors that should be considered when estimating the risk of being an SMA carrier. Since SMN2 plays a disease-modifying role, accurate determination of SMN2 copy numbers in SMA patients can serve as a useful prognostic tool. Therefore, information on the SMN2 genotype distributions in normal populations will be helpful in selecting appropriate reference samples for MLPA analysis. To determine SMA carrier frequencies and SMN genotype distribution, we determined the copy numbers of SMN1 and SMN2 genes using the MLPA assay in 100 unrelated Korean individuals with no family history of SMA. The frequency of SMA carriers in the Korean population appears to be 1 in 50, which indicates that the prevalence of SMA among Koreans is the same as that among individuals in the Western countries. Two of the 100 normal individuals enrolled in this study showed 3 copies of the SMN1 gene. Therefore, 1.0% of the 198 normal alleles in this population was estimated to be 2-copy alleles ('2+0' genotype). SMN2 copy numbers showed a high degree of individual variation. Our results showed that 64% of the individuals had 2 copies of SMN2, but 36% individuals had between 0, 1, or 3 copies of the gene.

Prenatal diagnosis of the spinal muscular atrophy type I using genetic information from archival slides and paraffin-embedded tissues

Spinal muscular atrophy (SMA) type I is a common severe autosomal recessive inherited neuromuscular disorder that has been mapped to chromosome 5q11.2-13.3. The survival motor neuron (SMN) gene, a candidate gene, is known to be deleted in 96% of patients with SMA type I. Presently, PCR and single strand conformation polymorphism (PCR-SSCP) analyses have been made possible for application to both archival slides and paraffin-embedded tissues. Archival materials represent valuable DNA resources for genetic diagnosis. We applied these methods for the identification of SMN gene of SMA type I in archival specimens for the prenatal diagnosis. In this study, we performed the prenatal diagnosis with chorionic villus sampling (CVS) cells on two women who had experienced neonatal death of SMA type I. DNA extraction was done from archival slide and tissue materials and PEP-PCR was performed using CVS cells. In order to identify common deletion region of SMN and neuronal apoptosis-inhibitory protein (NAIP) genes, cold PCR-SSCP and PCR-restriction site assay were carried out. Case 1 had deletions of the exons 7 and 8, and case 2 had exon 7 only on the telomeric SMN gene. Both cases were found to be normal on NAIP gene. These results were the same for both CVS and archival biopsied specimens. In both cases, the fetuses were, therefore, predicted to be at very high risk of being affected and the pregnancy were terminated. These data clearly demonstrate that archival slide and paraffin-embedded tissues can be a valuable source of DNA when the prenatal genetic diagnosis is needed in case any source for genetic analysis is not readily available due to previous death of the fetus or neonate.