New multiplex real-time PCR approach to detect gene mutations for spinal muscular atrophy

Molecular analysis of SMN2, NAIP, and GTF2H2 gene deletions and relationships with clinical subtypes of spinal muscular atrophy

SMA (spinal muscular atrophy) is an autosomal recessive neuromuscular disease that causes muscle atrophy and weakness. SMA is diagnosed by a homozygous deletion in exon 7 of the SMN1 gene. However, mutations in genes located in the SMA region, such as SMN2, NAIP, SERF1, and GTF2H2, may also contribute to the severity of the disease. Within our study's scope, 58 SMA patients who applied in 2018-2021 and 40 healthy controls were analyzed. The study retrospectively included the SMN1 and SMN2 copy numbers previously determined by the MLPA method. Then, NAIP gene analyses with the multiplex PCR method and GTF2H2 gene analyses with the RFLP method were performed. There was a significant correlation (p = 0.00001) between SMN2 copy numbers and SMA subtypes. Also, the NAIP gene (p = 0.01) and the GTF2H2 gene (p = 0.0049) revealed a significant difference between healthy and SMA subjects, whereas the SMA subtypes indicated no significant differences. We detected a significant correlation between clinical subtypes and HFMSE scores in 32 pediatric SMA patients compared (p = 0.01). While pediatric patients with GTF2H2 deletions demonstrated higher motor functions, and those with NAIP deletions demonstrated lower motor functions. In this study, we examined the relationship between NAIP and GTF2H2, called SMN region modifier genes, and the clinical severity of the disease in Turkish SMA patients. Despite its small scale, this research will benefit future investigations into the pathogenesis of SMA disease.

Association among biomarkers, phenotypes, and motor milestones in Chinese patients with 5q spinal muscular atrophy types 1-3

Background

Biomarkers can be used to assess the severity of spinal muscular atrophy (5q SMA; SMA). Despite their potential, the relationship between biomarkers and clinical outcomes in SMA remains underexplored. This study aimed to assess the association among biomarkers, phenotypes, and motor milestones in Chinese patients diagnosed with SMA.

Methods

We collected retrospective clinical and follow-up data of disease-modifying therapy (DMT)-naïve patients with SMA at our center from 2019 to 2021. Four biomarkers were included: survival motor neuron 2 (SMN2) copies, neuronal apoptosis inhibitory protein (NAIP) copies, full-length SMN2 (fl-SMN2), and F-actin bundling protein plastin 3 (PLS3) transcript levels. Data were analyzed and stratified according to SMA subtype.

Results

Of the 123 patients, 30 were diagnosed with Type 1 (24.3%), 56 with Type 2 (45.5%), and 37 with Type 3 (30.1%). The mortality rate for Type 1 was 50%, with median survival times of 2 and 8 months for types 1a and 1b, respectively. All four biomarkers were correlated with disease severity. Notably, fl-SMN2 transcript levels increased with SMN2 copies and were higher in Type 2b than those in Type 2a (p = 0.028). Motor milestone deterioration was correlated with SMN2 copies, NAIP copies, and fl-SMN2 levels, while PLS3 levels were correlated with standing and walking function.

Discussion

Our findings suggest that SMN2 copies contribute to survival and that fl-SMN2 may serve as a valuable biomarker for phenotypic variability in SMA Type 2 subtypes. These insights can guide future research and clinical management of SMA.

Systematic Review of Newborn Screening Programmes for Spinal Muscular Atrophy

Spinal muscular atrophy (SMA) is a genetic neuromuscular disorder causing the degeneration of motor neurons in the spinal cord. Recent studies suggest greater effectiveness of treatment in the presymptomatic stage. This systematic review synthesises findings from 37 studies (and 3 overviews) of newborn screening for SMA published up to November 2023 across 17 countries to understand the methodologies used; test accuracy performance; and timing, logistics and feasibility of screening. All studies screened for the homozygous deletion of SMN1 exon 7. Most (28 studies) used RT-PCR as the initial test on dried blood spots (DBSs), while nine studies also reported second-tier tests on DBSs for screen-positive cases. Babies testing positive on DBSs were referred for confirmatory testing via a range of methods. Observed SMA birth prevalence ranged from 1 in 4000 to 1 in 20,000. Most studies reported no false-negative or false-positive cases (therefore had a sensitivity and specificity of 100%). Five studies reported either one or two false-negative cases each (total of six cases; three compound heterozygotes and three due to system errors), although some false-negatives may have been missed due to lack of follow-up of negative results. Eleven studies reported false-positive cases, some being heterozygous carriers or potentially related to heparin use. Time to testing and treatment varied between studies. In conclusion, several countries have implemented newborn screening for SMA in the last 5 years using a variety of methods. Implementation considerations include processes for timely initial and confirmatory testing, partnerships between screening and neuromuscular centres, and timely treatment initiation.

Birth of spinal muscular atrophy unaffected baby from genetically at-risk parents following a pre-implantation genetic screening: A case report

Background

Spinal muscular atrophy (SMA) is characterized by the homozygous deletion of the survival motor neuron-1 gene. Pre-implantation genetic testing for monogenic diseases through in-vitrofertilization program was developed to provide a reliable genetic diagnostic method for SMA.

Case presentation

The couple who was confirmed as carriers of SMA visited the Morula IVF Clinic, Jakarta, Indenesia seeking for an in-vitro fertilization expert opinion in relation to the pre-implantation genetic testing for SMA. Utilizing polymerase chain reaction-restriction fragment length polymorphism, we have successfully screened for unaffected embryos that were characterized by a normal presence of the survival motor neuron-1 exon 7-8 and survival motor neuron-2 exon 7-8. The frozen embryo was subsequently transferred and a healthy unaffected female baby was born with undetected deletion of the survival motor neuron-1 gene.

Conclusion

This successful embryo pre-implantation screening case could potentially accommodate the demands of genetically at-risk couples who are apprehensive about conceiving a child who might inherit monogenic disorders such as SMA.

Investigation on the Effects of Modifying Genes on the Spinal Muscular Atrophy Phenotype

Introduction  Spinal muscular atrophy (SMA) is an autosomal recessive neuromuscular disorder caused by the degeneration of motor neurons, muscle weakness, and atrophy that leads to infant's death. The duplication of exon 7/8 in the SMN2 gene reduces the clinical severity of disease, and it is defined as modifying effect. In this study, we aim to investigate the expression of modifying genes related to the prognosis of SMA like PLS3 , PFN2 , ZPR1 , CORO1C , GTF2H2 , NRN1 , SERF1A , NCALD , NAIP , and TIA1.

Methods  Seventeen patients, who came to Trakya University, Faculty of Medicine, Medical Genetics Department, with a preliminary diagnosis of SMA disease, and eight healthy controls were included in this study after multiplex ligation-dependent probe amplification analysis. Gene expression levels were determined by real-time reverse transcription polymerase chain reaction and delta–delta CT method by the isolation of RNA from peripheral blood of patients and controls.

Results   SERF1A and NAIP genes compared between A group and B + C + D groups, and A group of healthy controls, showed statistically significant differences ( p  = 0.037, p  = 0.001).

Discussion   PLS3, NAIP , and NRN1 gene expressions related to SMA disease have been reported before in the literature. In our study, the expression levels of SERF1A , GTF2H2 , NCALD , ZPR1 , TIA1 , PFN2 , and CORO1C genes have been studied for the first time in SMA patients.

High-throughput screening reveals novel mutations in spinal muscular atrophy patients

BACKGROUND

Spinal muscular atrophy (SMA) is an autosomal recessive hereditary disease associated with severe muscle atrophy and weakness in the limbs and trunk. The discovery of mutated genes is helpful in diagnosis and treatment for SMA.

METHODS

Eighty-three whole blood samples were collected from 28 core families of clinically suspected SMA, and multiplex ligation probe amplification (MLPA) was performed. Afterwards, the complete gene sequence of SMN1 gene was detected. Furthermore, 20 SMA patients were selected from the 28 probands, and 5 non SMA children as controls. The Life Technologies SOLiD™ technology with mate-pair chemistry was utilized to conduct the whole exome high-throughput sequencing.

RESULTS

Twenty-two probands were SMA patients, 3 probands carriers, and 3 probands normal individuals. Moreover, 2 parents from 2 SMA families were with 3 SMN1 exon7 copies. Six SMN1 single nucleotide variants (SNVs) were identified in the 83 samples, and c.[84C > T], c.[271C > T], c.[-39A > G] and g.[70240639G > C] were novel. Compared with control group, 9102 mutation were selected out in SMA patients. SPTA1 mutation c.[-41_-40insCTCT], FUT5 SNV c.[1001A > G], and MCCC2 SNV c.[-117A > G] were the 3 most frequent mutations in SMA group (95, 85 and 75%, respectively).

CONCLUSIONS

We identified some mutations in both SMN1 and other genes, and c.[271C > T], c.[-41_-40insCTCT], c.[1001A > G] and c.[-117A > G] might be associated with the onset of SMA.