OBJECTIVE: To analyze variants of SMN gene in a Chinese pedigree affected with Spinal muscular atrophy (SMA). METHODS: A Chinese pedigree diagnosed at the Nanchang First Hospital in January 2020 was selected as the study subject. Peripheral blood samples were collected for the extraction of DNA. All exons of the SMN gene were detected by multiple ligation-dependent probe amplification (MLPA). Potential variants of the SMN gene were also detected by Whole exome sequencing (WES), and the result was verified by Sanger sequencing. cDNA extracted from fresh blood sample was used as a template to verify the location of variant on the SMN genes. RESULTS: The proband was found to harbor a heterozygous deletion of the SMN1 Exon7+Exon8, and a heterozygous c.81G>A variant. The SMN1 Exon7+Exon8 deletion was inherited from her father and grandmother, whilst the c.81G>A variant was inherited from her mother and maternal grandfather. Her aunt was also a carrier of the heterozygous deletion, while her paternal aunt, her husband, and their daughter were not. cDNA amplification and Sanger sequencing confirmed that the c.81G>A variant was located in the SMN1 gene. CONCLUSION MLPA combined with NGS and Sanger sequencing can identify compound heterozygous variants of the SMN gene in the SMA patients.
Female ; Humans ; Male ; DNA, Complementary ; East Asian People ; Fathers ; Mothers ; Muscular Atrophy, Spinal/diagnosis* ; Pedigree ; Survival of Motor Neuron 1 Protein/genetics*

OBJECTIVE: To carry out carrier screening for Spinal muscular atrophy (SMA) in reproductive-aged individuals from Dongguan region and determine the carrier frequency of SMN1 gene mutations. METHODS: Reproductive-aged individuals who underwent SMN1 genetic screening at the Dongguan Maternal and Child Health Care Hospital from March 2020 to August 2022 were selected as the study subjects. Deletions of exon 7 and 8 (E7/E8) of the SMN1 gene were detected by real-time fluorescence quantitative PCR (qPCR), and prenatal diagnosis was provided for carrier couples by multiple ligation-dependent probe amplification (MLPA). RESULTS: Among the 35 145 subjects, 635 were found to be carriers of SMN1 E7 deletion (586 with heterozygous E7/E8 deletion, 2 with heterozygous E7 deletion and homozygous E8 deletion, and 47 with sole heterozygous E7 deletion). The carrier frequency was 1.81% (635/35 145), with 1.59% (29/1 821) in males and 1.82% (606/33 324) in females. There was no significant difference between the two genders (χ² = 0.497, P = 0.481). A 29-year-old woman was found to harbor homozygous deletion of SMN1 E7/E8, and was verified to have a SMN1∶SMN2 ratio of [0∶4], none of her three family members with a [0∶4] genotype had clinical symptoms. Eleven carrier couples had accepted prenatal diagnosis, and one fetus was found to have a [0∶4] genotype, and the pregnancy was terminated. CONCLUSION This study has determined the SMA carrier frequency in Dongguan region for the first time and provided prenatal diagnosis for carrier couples. The data can provide a reference for genetic counseling and prenatal diagnosis, which has important clinical implications for the prevention and control of birth defects associated with SMA.
Humans ; Child ; Pregnancy ; Male ; Female ; Adult ; Homozygote ; Sequence Deletion ; Prenatal Diagnosis ; Genetic Testing ; Muscular Atrophy, Spinal/genetics* ; Survival of Motor Neuron 1 Protein/genetics* ; Genetic Carrier Screening

Spinal muscular atrophy (SMA) is an autosomal recessive motor neuron degenerative disease, which is the most common fatal neuromuscular disease in pediatrics with a high carrier frequency and can lead to progressive symmetrical muscle weakness and atrophy of the trunk and limbs. Preimplantation genetic testing (PGT) can be used to prevent the birth of children with SMA effectively. To standardize PGT technologies for SMA, experts from the fields of neurology, pediatrics and reproductive genetics have discussed and drafted this consensus for guiding its clinical application.
Child ; Consensus ; Genetic Testing ; Humans ; Muscular Atrophy, Spinal/genetics* ; Survival of Motor Neuron 1 Protein/genetics*

OBJECTIVE: To carry out prenatal diagnosis for families with high risk for spinal muscular atrophy (SMA) by using multiplex ligation-dependent probe amplification (MLPA). METHODS: Twenty-one families were enrolled. MLPA was used to detect copy numbers of SMN1 and SMN2 genes. Maternal contamination was excluded by using a short tandem repeat method. RESULTS: For 23 fetuses from the 21 families, 14 were identified as carriers, 1 as SMA patient, and 8 as normal. By linkage analysis of parental samples, three individuals were determined as silent (2+0) carriers. CONCLUSION MLPA can determine the carrier status of SMA. The identification of three silent (2+0) carriers among the 44 parental samples indicated a risk for such families, for which genetic counseling and reproduction guidance should be provided.
Female ; Genetic Counseling ; Heterozygote ; Humans ; Multiplex Polymerase Chain Reaction ; Muscular Atrophy, Spinal/genetics* ; Pregnancy ; Prenatal Diagnosis ; Survival of Motor Neuron 1 Protein/genetics*

OBJECTIVE: To perform carrier screening for spinal muscular atrophy (SMA) among 3049 reproductive-age individuals from Yunnan region and determine the copy number of survival motor neuron (SMN) gene and carrier frequencies. METHODS: Multiplex ligation-dependent probe amplification (MLPA) was used to determine the copy number of exon 7 of SMN1 and SMN2 genes and identify those with a single copy of SMN1 gene. Prenatal diagnosis was performed for couples whom were both found to be SMA carriers. RESULTS: In total 62 SMA carriers were identified among the 3049 subjects, which yielded a carrier frequency of 1 in 49 (2.03%). No statistical difference was found in the carrier frequency between males and females (1.91% vs. 2.30%, P>0.05). Respectively, 1.3% (41/3049) and 0.69% (21/3049) of the carriers were caused by heterozygous deletion and conversion of the SMN1 gene. The average copy number for SMN1 alleles was 1.99. Two couples were found to be both as SMA carriers, for whom the birth of an affected fetus was avoided by prenatal diagnosis. CONCLUSION No difference was found in the carrier frequency of SMA-related mutations between the two genders in Yunnan region, which was in keeping to an autosomal recessive inheritance pattern. Determination of the carrier frequency for SMA and SMN gene variants may provide a basis for genetic counseling and prenatal diagnosis for the disease.
China ; Female ; Genetic Carrier Screening ; Genetic Counseling ; Genetic Variation ; Heterozygote ; Humans ; Male ; Muscular Atrophy, Spinal ; genetics ; Pregnancy ; Prenatal Diagnosis ; Survival of Motor Neuron 1 Protein ; genetics ; Survival of Motor Neuron 2 Protein ; genetics

OBJECTIVE: To study the association of copy number of SMN1 and SMN2 with clinical phenotypes in children with spinal muscular atrophy (SMA). METHODS: A total of 45 children with SMA were enrolled. Multiplex ligation-dependent probe amplification was used to measure the gene copy numbers of SMN1 and SMN2. The association of copy number of SMN1 and SMN2 with clinical phenotypes was analyzed. RESULTS: Of the 45 children with SMA, 42 (93%) had a homozygous deletion of SMN1 exons 7 and 8, and 3 (7%) had a deletion of SMN1 exon 7 alone. No association was found between SMA clinical types and the deletion types of SMN1 exons 7 and 8 (P>0.05). There was a significant difference in the distribution of SMN2 gene copy numbers between the children with SMA and the healthy children (P<0.05). The children with SMA usually had two or three copies of SMN2 gene, while the healthy children usually had one or two copies of SMN2 gene. There was a significant difference in the distribution of SMN2 copy numbers among the children with different SMA clinical types (P<0.05). The children with two copies of SMN2 gene had a significantly lower age of onset than those with three or four copies. Most of the children with type I SMA had two or three copies of SMN2 gene. Most of the children with type II SMA had three copies of SMN2 gene. Most of the children with type III SMA had three or four copies of SMN2 gene. Children with a higher copy number of SMN2 gene tended to have an older age of onset and better motor function and clinical outcome, and there was a significant association between SMN2 gene copy number and clinical outcome (P<0.05). CONCLUSIONS The SMN2 gene can reduce the severity of SMA via the dosage compensation effect. SMN2 copy number is associated with the phenotype of SMA, and therefore, it can be used to predict disease severity.
Child ; Humans ; Muscular Atrophy, Spinal ; genetics ; Phenotype ; Survival of Motor Neuron 1 Protein ; genetics ; Survival of Motor Neuron 2 Protein ; genetics

Background: Spinal muscular atrophy (SMA) is caused by homozygous deletion or compound heterozygous mutation of survival motor neuron gene 1 (SMN1), which is the key to diagnose SMA. The study was to establish and evaluate a new diagnostic method for SMA. Methods: A total of 1494 children suspected with SMA were enrolled in this study. Traditional strategy, including multiplexed ligation-dependent probe amplification (MLPA) and TA cloning, was used in 1364 suspected SMA children from 2003 to 2014, and the 130 suspected SMA children were tested by a new strategy from 2015 to 2016, who were also verified by MLPA combined with TA cloning. The SMN1 and SMN2 were simultaneously amplified by polymerase chain reaction using the same primers. Mutation Surveyor software was used to detect and quantify the SMN1 variants by calculating allelic proportions in Sanger sequencing. Finally, turnaround time and cost of these two strategies were compared. Results: Among 1364 suspected SMA children, 576 children had SMN1 homozygous deletion and 27 children had SMN1 compound heterozygous mutation. Among the 130 cases, 59 had SMN1 homozygous deletion and 8 had heterozygous deletion: the SMN1-specific peak proportion on exon 7 was 34.6 ± 1.0% and 25.5 ± 0.5%, representing SMN1:SMN2 to be 1:2 and 1:3, respectively. Moreover, five variations, including p.Ser8Lysfs *23 (in two cases), p.Leu228*, p.Pro218Hisfs *26, p.Ser143Phefs*5, and p.Tyr276His, were detected in 6/8 cases with heterozygous deletion, the mutant allele proportion was 31.9%, 23.9%, 37.6%, 32.8%, 24.5%, and 23.6%, which was similar to that of the SMN1-specific site on exon 7, suggesting that those subtle mutations were located in SMN1. All these results were consistent with MLPA and TA cloning. The turnaround times of two strategies were 7.5 h and 266.5 h, respectively. Cost of a new strategy was only 28.5% of the traditional strategy. Conclusion Sanger sequencing combined with Mutation Surveyor analysis has potential application in SMA diagnosis.
Adolescent ; Child ; Child, Preschool ; Female ; Humans ; Infant ; Infant, Newborn ; Male ; Muscular Atrophy, Spinal ; diagnosis ; genetics ; Mutation ; Sequence Analysis, DNA ; methods ; Survival of Motor Neuron 1 Protein ; genetics ; Survival of Motor Neuron 2 Protein ; genetics

OBJECTIVETo explore the significance of SMN1 gene mutations among patients with spinal muscular atrophy (SMA) and the value of multiplex ligation dependent probe amplification (MLPA) for its diagnosis.

METHODSPotential mutations of the SMN1 gene were detected among 78 SMA patients with a MLPA assay.

RESULTSHomozygous deletion of SMN1 exons 7 and 8 was detected in 70 (89.7%) of all patients. Homozygous deletion of exons 7 and heterozygous deletion of exon 8 was detected in 3 patients (3.8%). Homozygous deletion of SMN1 exons 7 alone was detected in 3 patients (3.8%). Heterozygous deletion of SMN1 exons 7 and 8 was detected in 2 patients (2.6%). For 77 of the patients, both parents were found to carry heterozygous deletion of the SMN1 gene, which was consistent with the recessive inheritance of SMA. One patient with SMA type I was found to be rather rare. The patient was found to carry homozygous deletion of SMN1 exons 7 and 8, for which her mother was heterozygous, while no mutation was found in her father.

CONCLUSIONHomozygous deletion of the SMN1 gene have been detected in more than 95% of SMA patients. No homozygous deletion of exon 8 has been found. Homozygous deletion of exon 7 is more significant in the pathogenesis of SMA.

Exons ; Female ; Gene Deletion ; Humans ; Male ; Multiplex Polymerase Chain Reaction ; Muscular Atrophy, Spinal ; genetics ; Mutation ; Survival of Motor Neuron 1 Protein ; genetics

OBJECTIVETo explore the clinical application of droplet digital PCR (ddPCR) for genetic testing and prenatal diagnosis of spinal muscular atrophy (SMA) with deletion of SMN1 gene exon 7.

METHODSA total of 138 clinical samples, including 121 peripheral blood, 13 amniotic fluid, 2 umbilical cord blood and 2 chorionic villi from 56 SMA families, were tested by both ddPCR and multiplex ligation-dependent probe amplification (MLPA). Results of the two approaches were analyzed with commercial software QuantaSoft (ddPCR) and Coffalyser (MLPA), respectively.

RESULTSAmong the 138 cases, 25 had two copies, 84 had one copy, and 29 had null copy of exon 7 of the SMN1 gene. The results of ddPCR and MLPA were completely consistent.

CONCLUSIONAs a rapid, precise and economically efficient method, ddPCR will provide a new choice for genetic testing of SMA.

Adult ; DNA Copy Number Variations ; Family Health ; Female ; Gene Dosage ; Genetic Predisposition to Disease ; genetics ; Genetic Testing ; methods ; Humans ; Male ; Multiplex Polymerase Chain Reaction ; methods ; Muscular Atrophy, Spinal ; diagnosis ; embryology ; genetics ; Pedigree ; Pregnancy ; Prenatal Diagnosis ; methods ; Reproducibility of Results ; Sensitivity and Specificity ; Sequence Deletion ; Survival of Motor Neuron 1 Protein ; genetics

OBJECTIVETo verify the reliability of real-time PCR for the detection of genetic mutations underlying spinal muscular atrophy (SMA) and establish quality control for clinical testing.

METHODSThirty-five patients, 61 first-degree relatives, 61 healthy controls and 7 prenatal cases which were previously genotyped by multiplex ligation-dependent probe amplification (MLPA) were tested with Roche LightCycler 480 and Bio-Rad CFX96 (TM) real-time PCR machines for relative quantification of copy number of SMN1 exon 7.

RESULTSGenotyping detected by relative quantitative real-time PCR were consistent with the results of MLPA. Both types of real-time PCR machines could accurately distinguish different SMN1 copy numbers despite certain systematic differences between the two platforms.

CONCLUSIONThe reliability of real-time PCR assay for detecting SMA depends on quality control. Standard database generated with known SMN1 copy number variations should be established for different instruments.

Gene Dosage ; Humans ; Muscular Atrophy, Spinal ; genetics ; Mutation ; Real-Time Polymerase Chain Reaction ; methods ; Survival of Motor Neuron 1 Protein ; genetics