Clinical profile of genetically confirmed Spinal Muscular Atrophy (SMA) Among Filipino children less than 18 years old

@#Spinal muscular atrophy (SMA) is the most common inherited lethal disease in children. Confirmatory diagnosis is based on molecular genetic testing of survival motor neuron (SMN) genes. We aimed to describe the phenotypic presentation of Filipino infants and children with SMA based on the copy number analysis of SMN genes. Medical records of 17 Filipino children were reviewed from January 2017 to December 2019. De-identified clinical data fulfilled the diagnostic criteria defined by the International SMA Consortium. Among Filipino children, the predominant SMA type by copy number was type I having two copies of SMN2 gene. The clinical severity based on symptom onset and highest functional motor capacity attained correlated with SMN2 copy number congruent with existing data. A significant time lag between symptom onset to confirmation of genetic diagnosis was noted. Nine out of the 17 (52%) children did not have a family history of the disease, raising the possibility of mutation carriers in these families since the incidence of de novo mutations in literature is about 2%. These data offered the first epidemiological pattern of genetically confirmed SMA among Filipino children; provided additional information for genetic counselling; and an avenue to consider pre-symptomatic newborn screening and carrier testing that would change proactive measures and opportunities for therapy. These measures unavoidably will decrease the incidence and prevalence of disease in the future.

Effects of survival motor neuron gene knockdown on acute kidney injury induced by cisplatin in mice / 中华肾脏病杂志

Objective:To investigate the role of survival motor neuron ( SMN) gene knockout in mice with cisplatin-induced acute kidney injury (AKI). Methods:A mouse model (C57BL/6) of cisplatin-induced AKI was constructed. Twenty male wild type (WT) and SMN+/- mice weighing 22-24 g were randomly divided into four groups: WT mice with saline injection group (WT vehicle, n=5), SMN+/- mice with saline injection group ( SMN+/- vehicle, n=5), WT mice with cisplatin injection group (WT cisplatin, n=5) and SMN+/- mice with cisplatin injection group ( SMN+/- cisplatin, n=5). Mice were injected intraperitoneally with 20 mg/kg cisplatin or 0.9% saline. 72 hours later, the mice were sacrificed, and serum and kidney tissues were collected. The real time PCR and Western blotting were used to measure the expression levels of SMN mRNA and protein. The sarcosine oxidation and urease method were used to measure serum creatinine (Scr) and blood urea nitrogen (BUN) levels. Renal pathologic changes were observed by PAS staining. TUNEL immunofluorescence assay was used to detect the level of apoptosis. Western blotting and immunohistochemistry were used to detect the protein expression levels of apoptosis index poly (ADP-ribose) polymerase (PARP) and endoplasmic reticulum stress index CHOP. Results:Compared with WT mice, SMN mRNA and protein expression levels were lower in SMN+/- mice, and the expression level of SMN mRNA and protein was further decreased after intraperitoneal cisplatin injection (all P<0.05). Compared with WT mice with saline injection group, WT mice with cisplatin injection group had higher levels of Scr, BUN, tubular damage scores, TUNEL positive cell numbers, PARP and CHOP, while the expression levels of above indexes in the SMN+/- mice with cisplatin injection group were higher than those in the WT mice with cisplatin injection group (all P<0.05). Conclusions:SMN gene knockout can aggravate renal pathological damage and apoptosis of renal tubular epithelial cell in cisplatin-induced AKI mice. SMN may be a potential therapeutic target of AKI.

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.

Progress on genetics and therapy in the spinal muscular atrophy / 临床儿科杂志

Spinal muscular atrophy (SMA) is a group of neuromuscular disorders, caused by degeneration of the motor neurons in the anterior horn of the spinal cord, with prevalence of about 1 in 6000 to 1 in 10000 in newborn. The gene carrying frequency is about 1 in 40 to 1 in 50 all over the world. SMA is one of the most common autosomal recessive diseases causing infant death. SMA mainly refers to SMN1 dependent caused by SMN1 gene mutations. Noninvasiveness and specificity make genetic testing a recommended method for diagnosis of SMA. In addition to conventional methods such as neural nutrition, muscle exercise, etc., there is no specific treatment for SMA up to now. Nevertheless, HDAC inhibitors deserve attention as they are the only drugs completed Phase Ⅲ clinical trials to date. Furthermore, other ways as small-molecule SMN enhancers, induced pluripotent stem cell (iPSC), antisense oligonucleotides to correct SMN2 splicing, etc, were still on the way of in vitro stage at present.

Clinical Characteristics of Spinal Muscular Atrophy in Korea Confirmed by Genetic Analysis

The objective of this study was to review the clinical characteristics of patients with spinal muscular atrophy and to emphasize the importance of performing genetic mutational analysis at initial patient assessment. This is a single center oriented, retrospective, and descriptive study conducted in Seoul, South Korea. Genetic mutational analysis to detect the deletion of exon 7 of the SMN1 gene on chromosome 5q13 was performed by multiplex ligation-dependent probe amplification. Clinical features, electrodiagnostic study results, muscle biopsy results, and laboratory test results were reviewed from patient medical records. Of all 28 patients (15 males and 13 females), all showed bilateral symmetric proximal dominant weakness. Among them, 3 patients were classified as type I, 14 patients as type II, and 11 patients as type III. Twenty-five patients had scoliosis and eight of these patients received surgical treatment for scoliosis with improvement in clinical outcomes. Ventilator support was used in 15 patients. In terms of the diagnostic process, 15 patients had completed an electrodiagnostic study and muscle biopsy before genetic testing, and six of these patients were initially misdiagnosed with myopathy. Owing to the similar clinical features of SMA and congenital myopathy, an electrodiagnostic study and muscle biopsy could create confusion in the correct diagnosis in some cases. Therefore, it is recommended that genetic mutation analysis should be conducted along with an electrodiagnostic study or muscle biopsy in the diagnostic process for spinal muscular atrophy.

Spinal Muscular Atrophy: Review of a Child Onset Disease.

Spinal Muscular Atrophy (SMA) is a group of inherited disorders that involve mainly bulbar and spinal motor neurons; causing muscle weakness and atrophy of proximal and symmetrical predominantly in lower extremities, without affecting the facial muscles and the intellectual ability. It is also unclear if SMA is a developmental or a neurodegenerative disease and occurs predominantly in childhood. The continuous clinical spectrum of SMA has been divided into 3 types based on the age at onset and highest motor milestones achieved. SMA type I was described by Hoffman in 1894 and in 1900 was reported as a disease characterized by hypotonia during the first 3 months of life, as well, is considered as the leading cause of death in children under two years of age among genetic diseases worldwide. SMA type II patients can achieve sitting but not walking. While SMA type III patients achieve full milestones with a progressive loss of walking ability. Deterioration in muscle strength and motor function eventually occurs in SMA type II and III. SMA occurs due to depletion of SMN, a ubiquitously expressed protein, which in all cells regulates RNA biogenesis and splicing through its role in the assembly of small nuclear ribonucleoprotein (snRNP) complexes.

Type 0 Spinal Muscular Atrophy with Multisystem Involvement.

Background: The classical forms of severe Spinal Muscular Atrophy type is well recognized by pediatricians. Case Characteristics: A hypotonic neonate with severe respiratory distress at birth. Observation: Homozygous absence of exons 7 of the Survival Motor Neuron I gene. Outcome: Died 108 days after admission when respiratory support was withdrawn at the request of the parents. Message: Spinal Muscular Atrophy should be kept in mind in the differential diagnosis for unexplained severe generalized hypotonia and severe respiratory distress immediately after birth in the neonates.

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.

A Case of Exon 7 and 8 Deletion of Survival Motor Neuron Gene in Spinal Muscular Atrophy / 대한소아신경학회지

Spinal muscular atrophy(SMA) is a genetic disorder of the motor neurons that cause muscular weakness and muscular atrophy due to anterior horn cell degeneration. Classic spinal muscular atrophy patient is caused by mutation in the chromosome 5(q11.2-q13.3), and the majority of the patient shows homozygous deletion of the telomeric survival motor neuron(SMN) gene in the chromosome 5. Deletion of exon 7 and 8 of the SMN gene and deletion of exon 4 and 5 of the neuronal apoptosis inhibitory protein(NAIP) are typically observed in SMA patients. The SMN protein plays a role in an essential cell metabolism process, the splicing of pre mRNA in the spliceosomes. We report a 7 month old male with SMA. He showed rapidly aggrdvatial muscular weakness and died at 7 months. His DNA analysis proved deletion of exon 7 and 8 of the telomeric copy of the SMN 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.

Molecular biological diagnosis of Spinal Muscular atrophy

Spinal muscular atrophy(SMA) is the second most common fatal disease of childhood with autosomal dominant mode of inheritance, and in its less severe form the third most common neuromuscular disease of childhood after Duchenne muscular dystrophy. The genetic defect was found to be on the long arm of chromosome 5(5q11.2-q13.3) where many genes and microsatellite markers were missing. One of the most important genes is the Survival Motor Neuron(SMN) gene which is homozygously missing in 90% of SMA patients. Another important gene, the Neuronal Apoptosis Inhibitory Protein(NAIP) gene was found to be defective in 67% of SMA type I patients. Studies so far suggest SMA occurs when the genes on the long arm of chromosome 5 are mutated or deleted. Recently our hospital encountered 2 SMA patients of type I and II respectively. These patients both had homozygously defective SMN genes but intact NAIP genes. We are reporting these cases with bibliographic review and discussion. Korean SMA patients presumably have defects in SMN genes similar to those found in European patients, although the siginificance of NAIP genes remains to be established. SMN gene defects can be easily diagnosed using PCR and restriction enzymes, and this method could be applied towards convenient prenatal diagnosis and towards screening for family members at risk.