Malnutrition in Spinal Muscular Atrophy Type I: Case Report of a Novel Nutritional Intervention With Improved Growth and Function While Receiving Parallel Gene Splicing Therapies

Children with spinal muscular atrophy (SMA) frequently experience feeding intolerance and diminished growth. Although splicing modulators to prevent symptoms are available worldwide, adequate nutrition to support growth, development, and improved quality of life remains essential. We present a case study of a one-year-old malnourished male with SMA type I who achieved improved growth and feeding tolerance with a human milk (HM)-derived nutrition intervention. Despite feeding with appropriately balanced semielemental formula, he remained severely malnourished after two months of hospitalization. Feeds were partially replaced with HM-based diet plus a HM-based fat modular. Feeding tolerance, fecal calprotectin levels, and z scores for weight and length improved while receiving the HM-based intervention. We hypothesize that the HM-based feeding reduced intestinal inflammation by diminishing pathogenic elements of his microbiome. Owing to their aberrant fatty acid metabolism, patients with SMA are uniquely positioned to benefit from HM-based nutrient acquisition even while receiving splicing modulators to stabilize the disease process.

[Experience of the treatment of spinal muscular atrophy type 3 Kugelberg-Welander with Nusinersen]

Before the advent of pathogenetic therapy, the diagnosis of spinal muscular atrophy (SMA) meant the loss of all hopes for recovery and the patient's setting on the path of a steady decline in motor functions, a deterioration in the quality of life and, ultimately, inevitable early death. Currently, new methods of pathogenetic therapy with nusinersen and risdiplam, as well as etiological therapy with onasemnogene abeparvovec, are available in the Russia. Nusinersen is an antisense oligonucleotide that modifies splicing of the SMN2 gene to increase production of normal full-length motor neuron survival protein, which is deficient in SMA. The mechanism of action of Nusinersen is based on the activation of the disabled exon 7 of the SMN2 gene. The article describes an example of long-term effective treatment using pathogenetic therapy of a patient diagnosed with SMA type 3.

Spinal muscular atrophy in Ghanaian children confirmed by molecular genetic testing: a case series

Spinal muscular atrophy (SMA) is an autosomal recessive inherited motor neuron disease characterized by progressive muscle weakness due to degeneration and loss of the anterior horn cells in the spinal cord and the brain stem nuclei from foetal life through infancy and childhood. SMA is prevalent in Ghanaian children, though not widely reported. Cases are likely missed or misdiagnosed due to lack of expertise and investigations. Newborn screening is not currently available in Ghana. The management remains supportive as newly approved genetic modifications therapies are currently not available. We present a retrospective folder review of children attending a tertiary pediatric neurology clinic who were diagnosed with SMA and confirmed by molecular genetic testing. Between January 2018 and August 2021, five (5) children from three families had molecular genetic tests confirming their diagnosis of SMA. Three (3) children had SMA I phenotype while 2 had SMA III phenotype. Two (2) of the 3 children with SMA I died from respiratory complications. The last surviving child with SMA I was diagnosed through newborn screening program overseas and received gene modification therapy. Careful history and physical examination remain the best approach to diagnosis as confirmatory genetic testing and supplemental investigations are not readily available. The current management of the children with SMA in Ghana include respiratory care, physiotherapy, and genetic counselling. Genetic modification therapies are currently not available.

Sleep disordered breathing in infants identified through newborn screening with spinal muscular atrophy

BACKGROUND

Spinal muscular atrophy (SMA) is a genetic disorder that may result in neuromuscular weakness and respiratory insufficiency. Gene replacement therapy has changed the trajectory of this condition, but long-term outcomes related to sleep disordered breathing are not known.

METHODS

This was a retrospective review of infants with SMA identified via newborn screening who subsequently received onasemnogene abeparvovec at the Hospital for Sick Children (Ontario, Canada). Polysomnograms were conducted at the time of confirmed diagnosis as well as regularly thereafter.

RESULTS

Eleven children (4 female) were identified via newborn screen (7 with 2 copies of the SMN2 gene and 4 with 3 copies of the SMN2 gene) and received onasemnogene abeparvovec at a median age of 3.6 weeks. All eleven infants met criteria for sleep disordered breathing based on their first completed polysomnograms but improved over time. Three infants required respiratory technology, including a premature infant who was prescribed nocturnal supplemental oxygen therapy for central sleep apnea and two symptomatic infants with neuromuscular weakness who required nocturnal noninvasive ventilation. We did not find a correlation between motor scores and polysomnogram parameters.

CONCLUSION

Children treated with onasemnogene abeparvovec have reduced sleep disordered breathing over time. Polysomnograms revealed abnormal parameters in all children, but the clinical significance of these findings was unclear for children who were asymptomatic for sleep disordered breathing or neuromuscular weakness. These results highlight the need to evaluate both motor scores and respiratory symptoms to ensure a holistic evaluation of clinical status.

Onasemnogene abeparvovec gene replacement therapy for the treatment of spinal muscular atrophy: a real-world observational study

Spinal muscular atrophy (SMA) is a genetically inherited recessive neuromuscular disease that causes muscular atrophy and weakness. Onasemnogene abeparvovec (formerly AVXS-101, Zolgensma®, Novartis) is a targeted therapy approved to treat patients with SMA in >40 countries worldwide. This study describes the clinical efficacy and tolerability of gene replacement therapy with onasemnogene abeparvovec over a 3-month period in 9 SMA type 1 patients aged 1.7-48 months, with 7 patients on stable nusinersen (i.e., had received all four nusinersen loading doses before inclusion in this study). Liver function (alanine aminotransferase, aspartate aminotransferase, total bilirubin), troponin I, platelet counts, creatinine levels, and motor function (CHOP-INTEND) were monitored. For the seven patients on stable nusinersen, the median baseline CHOP-INTEND score increased significantly during nusinersen treatment (Wilcoxon signed-rank test p = 0.018) and at 3 months after switching to onasemnogene abeparvovec (Wilcoxon signed-rank test p = 0.0467). We also identified two patients who responded poorly to nusinersen but showed the largest increase in baseline CHOP-INTEND scores at 1 and 3 months after switching, which could suggest that poor responders to nusinersen may respond favorably to onasemnogene abeparvovec. No unknown adverse events occurred. One patient developed moderate/severe thrombocytopenia 1 week after onasemnogene abeparvovec administration that resolved after treatment. Our study suggests the possibility of a change in the dynamic of CHOP-INTEND for patients who respond poorly to nusinersen after switching therapy to onasemnogene abeparvovec. Alternatively, patient age at treatment initiation may impact the response to onasemnogene abeparvovec. Testing in larger patient populations must be undertaken to assess the plausibility of these hypotheses.

Prevalence of Spinal Muscular Atrophy in the Era of Disease-Modifying Therapies: An Italian Nationwide Survey

OBJECTIVE

Spinal muscular atrophy (SMA) is a neurodegenerative disorder caused by mutations in the SMN1 gene. The aim of this study was to assess the prevalence of SMA and treatment prescription in Italy.

METHODS

An online survey was distributed to 36 centers identified by the Italian government as referral centers for SMA. Data on the number of patients with SMA subdivided according to age, type, SMN2 copy number, and treatment were collected.

RESULTS

One thousand two hundred fifty-five patients with SMA are currently followed in the Italian centers with an estimated prevalence of 2.12/100,000. Of the 1,255, 284 were type I, 470 type II, 467 type III, and 15 type IV with estimated prevalence of 0.48, 0.79, 0.79 and 0.02/100,000, respectively. Three patients with SMA 0 and 16 presymptomatic patients were also included. Approximately 85% were receiving one of the available treatments. The percentage of treated patients decreased with decreasing severity (SMA I: 95.77%, SMA II: 85.11%, SMA III: 79.01%).

DISCUSSION

The results provide for the first time an estimate of the prevalence of SMA at the national level and the current distribution of patients treated with the available therapeutical options. These data provide a baseline to assess future changes in relation to the evolving therapeutical scenario.

Sex Difference in Spinal Muscular Atrophy Patients - are Males More Vulnerable?

BACKGROUND

Sex is a significant risk factor in many neurodegenerative disorders. A better understanding of the molecular mechanisms behind sex differences could help develop more targeted therapies that would lead to better outcomes. Untreated spinal muscular atrophy (SMA) is the leading genetic motor disorder causing infant mortality. SMA has a broad spectrum of severity ranging from prenatal death to infant mortality to normal lifespan with some disability. Scattered evidence points to a sex-specific vulnerability in SMA. However, the role of sex as a risk factor in SMA pathology and treatment has received limited attention.

OBJECTIVE

Systematically investigate sex differences in the incidence, symptom severity, motor function of patients with different types of SMA, and in the development of SMA1 patients.

METHODS

Aggregated data of SMA patients were obtained from the TREAT-NMD Global SMA Registry and the Cure SMA membership database by data enquiries. Data were analyzed and compared with publicly available standard data and data from published literature.

RESULTS

The analysis of the aggregated results from the TREAT-NMD dataset revealed that the male/female ratio was correlated to the incidence and prevalence of SMA from different countries; and for SMA patients, more of their male family members were affected by SMA. However, there was no significant difference of sex ratio in the Cure SMA membership dataset. As quantified by the clinician severity scores, symptoms were more severe in males than females in SMA types 2 and 3b. Motor function scores measured higher in females than males in SMA types 1, 3a and 3b. The head circumference was more strongly affected in male SMA type 1 patients.

CONCLUSIONS

The data in certain registry datasets suggest that males may be more vulnerable to SMA than females. The variability observed indicates that more investigation is necessary to fully understand the role of sex differences in SMA epidemiology, and to guide development of more targeted treatments.

Onasemnogene abeparvovec for presymptomatic infants with three copies of SMN2 at risk for spinal muscular atrophy: the Phase III SPR1NT trial

Most children with biallelic SMN1 deletions and three SMN2 copies develop spinal muscular atrophy (SMA) type 2. SPR1NT ( NCT03505099 ), a Phase III, multicenter, single-arm trial, investigated the efficacy and safety of onasemnogene abeparvovec for presymptomatic children with biallelic SMN1 mutations treated within six postnatal weeks. Of 15 children with three SMN2 copies treated before symptom onset, all stood independently before 24 months (P < 0.0001; 14 within normal developmental window), and 14 walked independently (P < 0.0001; 11 within normal developmental window). All survived without permanent ventilation at 14 months; ten (67%) maintained body weight (≥3rd WHO percentile) without feeding support through 24 months; and none required nutritional or respiratory support. No serious adverse events were considered treatment-related by the investigator. Onasemnogene abeparvovec was effective and well-tolerated for presymptomatic infants at risk of SMA type 2, underscoring the urgency of early identification and intervention.

Dual SMN inducing therapies can rescue survival and motor unit function in symptomatic ∆7SMA mice

Spinal muscular atrophy (SMA) is an autosomal recessive disease characterized by survival motor neuron (SMN) protein deficiency which results in motor neuron loss and muscle atrophy. SMA is caused by a mutation or deletion of the survival motor neuron 1 (SMN1) gene and retention of the nearly identical SMN2 gene. SMN2 contains a C to T change in exon 7 that results in exon 7 exclusion from 90% of transcripts. SMN protein lacking exon 7 is unstable and rapidly degraded. The remaining full-length transcripts from SMN2 are insufficient for normal motor neuron function leading to the development of SMA. Three different therapeutic approaches that increase full-length SMN (FL-SMN) protein production are approved for treatment of SMA patients. Studies in both animal models and humans have demonstrated increasing SMN levels prior to onset of symptoms provides the greatest therapeutic benefit. Treatment of SMA, after some motor neuron loss has occurred, is also effective but to a lesser degree. The SMN∆7 mouse model is a well characterized model of severe or type 1 SMA, dying at 14 days of age. Here we treated three groups of ∆7SMA mice starting before, roughly during, and after symptom onset to determine if combining two mechanistically distinct SMN inducing therapies could improve the therapeutic outcome both before and after motor neuron loss. We found, compared with individual therapies, that morpholino antisense oligonucleotide (ASO) directed against ISS-N1 combined with the small molecule compound RG7800 significantly increased FL-SMN transcript and protein production resulting in improved survival and weight of ∆7SMA mice. Moreover, when give late symptomatically, motor unit function was completely rescued with no loss in function at 100 days of age in the dual treatment group. We have therefore shown that this dual therapeutic approach successfully increases SMN protein and rescues motor function in symptomatic ∆7SMA mice.

Early Cost-Effectiveness of Onasemnogene Abeparvovec-xioi (Zolgensma) and Nusinersen (Spinraza) Treatment for Spinal Muscular Atrophy I in The Netherlands With Relapse Scenarios

OBJECTIVES

Onasemnogene Abeparvovec-xioi (AVXS-101) is a gene therapy intended for curative treatment of spinal muscular atrophy (SMA) with an expected price of around €2 000 000. The goal of this study is to perform a cost-effectiveness analysis of treatment of SMA I patients with AVXS-101 in The Netherlands including relapse scenarios.

METHODS

An individual-based state-transition model was used to model treatment effect and survival of SMA I patients treated with AVXS-101, nusinersen and best supportive care (BSC). The model included five health states: three health states according to SMA types, one for permanent ventilation and one for death. Deterministic and probabilistic sensitivity analyses were performed. Effects of relapsing to lower health states in the years following treatment was explored.

RESULTS

The base-case incremental cost-effectiveness ratio (ICER) for AVXS-101 versus BSC is €138 875/QALY, and €53 447/QALY for AVXS-101 versus nusinersen. If patients relapse within 10 years after treatment with AVXS-101, the ICER can increase up to 6-fold, with effects diminishing thereafter. Only relapses occurring later than 50 years after treatment have a negligible effect on the ICER. To comply with Dutch willingness-to-pay reference values, the price of AVXS-101 must decrease to €680 000.

CONCLUSIONS

Based on this model, treatment with AVXS-101 is unlikely to be cost-effective under Dutch willingness-to-pay reference values. Uncertainty regarding the long-term curative properties of AVXS-101 can result in multiplication of the ICER. Decision-makers are advised to appropriately balance these uncertainties against the price they are willing to pay now.

Does Cost-Effectiveness Analysis Overvalue Potential Cures? Exploring Alternative Methods for Applying a "Shared Savings" Approach to Cost Offsets

OBJECTIVES

To evaluate alternative methods to calculate and/or attribute economic surplus in the cost-effectiveness analysis of single or short-term therapies.

METHODS

We performed a systematic literature review of articles describing alternative methods for cost-effectiveness analysis of potentially curative therapies whose assessment using traditional methods may suggest unaffordable valuations owing to the magnitude of estimated long-term quality-adjusted life-year (QALY) gains or cost offsets. Through internal deliberation and discussion with staff at the Health Technology Assessment bodies in England and Canada, we developed the following 3 alternative methods for further evaluation: (1) capping annual costs in the comparator arm at $150 000 per year; (2) "sharing" the economic surplus with the health sector by apportioning only 50% of cost offsets or 50% of cost offsets and QALY gains to the value of the therapy; and (3) crediting the therapy with only 12 years of the average annual cost offsets or cost offsets and QALY gains over the lifetime horizon. The impact of each alternative method was evaluated by applying it in an economic model of 3 hypothetical condition-treatment scenarios meant to reflect a diversity of chronicity and background healthcare costs.

RESULTS

The alternative with greatest impact on threshold price for the fatal pediatric condition spinal muscular atrophy type 1 was the 12-year cutoff scenario. For a hypothetical one-time treatment for hemophilia A, capping cost offsets at $150 000 per year had the greatest impact. For chimeric antigen receptor T-cell treatment of non-Hodgkin's lymphoma, capping cost offsets or using 12-year threshold had little impact, whereas 50% sharing of surplus including QALY gains and cost offsets greatly reduced threshold pricing.

CONCLUSIONS

Health Technology Assessment bodies and policy makers will wrestle with how to evaluate single or short-term potentially curative therapies and establish pricing and payment mechanisms to ensure sustainability. Scenario analyses using alternative methods for calculating and apportioning economic surplus can provide starkly different assessment results. These methods may stimulate important societal dialogue on fair pricing for these novel treatments.

Nusinersen Modulates Proteomics Profiles of Cerebrospinal Fluid in Spinal Muscular Atrophy Type 1 Patients

Spinal muscular atrophy (SMA) type 1 is a severe infantile autosomal-recessive neuromuscular disorder caused by a survival motor neuron 1 gene (SMN1) mutation and characterized by progressive muscle weakness. Without supportive care, SMA type 1 is rapidly fatal. The antisense oligonucleotide nusinersen has recently improved the natural course of this disease. Here, we investigated, with a functional proteomic approach, cerebrospinal fluid (CSF) protein profiles from SMA type 1 patients who underwent nusinersen administration to clarify the biochemical response to the treatment and to monitor disease progression based on therapy. Six months after starting treatment (12 mg/5 mL × four doses of loading regimen administered at days 0, 14, 28, and 63), we observed a generalized reversion trend of the CSF protein pattern from our patient cohort to that of control donors. Notably, a marked up-regulation of apolipoprotein A1 and apolipoprotein E and a consistent variation in transthyretin proteoform occurrence were detected. Since these multifunctional proteins are critically active in biomolecular processes aberrant in SMA, i.e., synaptogenesis and neurite growth, neuronal survival and plasticity, inflammation, and oxidative stress control, their nusinersen induced modulation may support SMN improved-expression effects. Hence, these lipoproteins and transthyretin could represent valuable biomarkers to assess patient responsiveness and disease progression.

Nusinersen for spinal muscular atrophy type 1: Real-world respiratory experience

BACKGROUND

The emergence of new treatments for spinal muscular atrophy (SMA) is revolutionary, especially for SMA type 1 (SMA1). Data on respiratory outcomes remain sparse and rely mostly on randomized clinical trials. We report our experience of Nusinersen-treated SMA1 patients in real-world settings.

METHODS

Data from SMA1 patients treated with Nusinersen were prospectively collected between 1/2017 and 1/2020. Respiratory variables included the use of assisted ventilation, the use of mechanical insufflation-exsufflation (MIE), respiratory complications, and death or treatment cessation due to respiratory reasons.

RESULTS

Twenty SMA1 patients were assessed before and after 2 years of Nusinersen treatment which was initiated at a median age of 13.5 months (range, 1-184). At baseline, 16 patients were using assisted ventilation, eight noninvasive and eight invasive. Twelve patients were using permanent ventilation and four partial ventilation. After 2 years of treatment, there was no change in respiratory support among ventilated patients. All four patients who were free from respiratory support at baseline required the initiation of assisted ventilation during the study period. All 20 patients used MIE after 2 years of treatment. Two patients died from acute respiratory failure and one sustained severe brain injury. Four patients had chronic and/or recurrent atelectasis.

CONCLUSION

Most of our patients were stable in their need for assisted ventilation and did not worsen as expected in SMA1, nor did they improve as might be hoped. Future studies are needed to determine if earlier treatment with Nusinersen might result in respiratory outcomes superior to those reported in this real-life study.

Nusinersen treatment of spinal muscular atrophy - a systematic review

INTRODUCTION

5q spinal muscular atrophy (SMA) is an autosomal recessive neuromuscular disorder caused by insufficient survival motor neuron protein. Untreated SMA involves death or permanent respiratory support (type 1), inability to walk (type 2) or ability to walk (type 3). The incidence of SMA is 1 in 7,500 live births, equivalant to eight children being born with SMA in Denmark annually.

METHODS

We undertook a systematic review of the efficacy of nusinersen as SMA treatment. We included randomised controlled trials and cohort studies. Our primary endpoints were survival without permanent respiratory support and change in motor function.

RESULTS

We identified 658 articles and included 13 of these (two randomised controlled trials and 11 cohort studies). Nusinersen increased survival without permanent respiratory support in SMA type 1 and increased motor function development in types 1-3. Nusinersen treatment before symptom onset in children with presymptomatic SMA produced near-normal motor development. So far, nusinersen has only minor safety concerns mostly related to the lumbar puncture.

CONCLUSIONS

Nusinersen increased survival without permanent ventilatory support in children with SMA type 1. Improvements in SMA type 2 and 3 were less evident. Better outcomes were seen in young children with a short disease duration, particularly in children receiving nusinersen before symptom onset. Newborn SMA screening may facilitate presymptomatic treatment with splice modification (nusinersen, risdiplam) or gene implantation therapy (AVXS-101, zolgensma).

Whole-blood dysregulation of actin-cytoskeleton pathway in adult spinal muscular atrophy patients

OBJECTIVE

Recent advances in therapeutics have improved prognosis for severely affected spinal muscular atrophy (SMA) type 1 and 2 patients, while the best method of treatment for SMA type 3 patients with later onset of disease is unknown. To better characterize the SMA type 3 population and provide potential therapeutic targets, we aimed to understand gene expression differences in whole blood of SMA type 3 patients (n = 31) and age- and gender-matched controls (n = 34).

METHODS

We performed the first large-scale whole blood transcriptomic screen with L1000, a rapid, high-throughput gene expression profiling technology that uses 978 landmark genes to capture a representation of the transcriptome and predict expression of 9196 additional genes.

RESULTS

The primary downregulated KEGG pathway in adult SMA type 3 patients was "Regulation of Actin Cytoskeleton," and downregulated expression of key genes in this pathway, including ROCK1, RHOA, and ACTB, was confirmed in the same whole blood samples using RT-qPCR. SMA type 3 patient-derived fibroblasts had lower expression of these genes compared to control fibroblasts from unaffected first-degree relatives. Overexpression of SMN levels using an AAV vector in fibroblasts did not normalize ROCK1, RHOA, and ACTB mRNA expression, indicating the involvement of additional genes in cytoskeleton dynamic regulation.

INTERPRETATION

Our findings from whole blood and patient-derived fibroblasts suggest SMA type 3 patients have decreased expression of actin cytoskeleton regulators. These observations provide new insights and potential therapeutic targets for SMA patients with longstanding denervation and secondary musculoskeletal pathophysiology.

Clinical Service Delivery of Noninvasive Prenatal Diagnosis by Relative Haplotype Dosage for Single-Gene Disorders

A relative haplotype dosage (RHDO)-based method was developed and implemented into routine clinical practice for noninvasive prenatal diagnosis (NIPD) of multiple single-gene disorders: spinal muscular atrophy, Duchenne and Becker muscular dystrophies, and cystic fibrosis. This article describes the experiences of the first 152 pregnancies to have NIPD by RHDO as part of a routine clinical service. Provision of results within a clinically useful time frame (mean, 11 calendar days) was shown to be possible, with a very low failure rate (4%), none being due to a technical failure. Where follow-up confirmatory testing was performed for audit purposes, 100% concordance was seen with the NIPD result, and no discrepancies have been reported. The robust performance of the assay, together with high sensitivity and specificity, demonstrates that NIPD by RHDO is feasible for use in a clinical setting.

GARS-related disease in infantile spinal muscular atrophy: Implications for diagnosis and treatment

The majority of patients with spinal muscular atrophy (SMA) identified to date harbor a biallelic exonic deletion of SMN1. However, there have been reports of SMA-like disorders that are independent of SMN1, including those due to pathogenic variants in the glycyl-tRNA synthetase gene (GARS1). We report three unrelated patients with de novo variants in GARS1 that are associated with infantile-onset SMA (iSMA). Patients were ascertained during inpatient hospital evaluations for complications of neuropathy. Evaluations were completed as indicated for clinical care and management and informed consent for publication was obtained. One newly identified, disease-associated GARS1 variant, identified in two out of three patients, was analyzed by functional studies in yeast complementation assays. Genomic analyses by exome and/or gene panel and SMN1 copy number analysis of three patients identified two previously undescribed de novo missense variants in GARS1 and excluded SMN1 as the causative gene. Functional studies in yeast revealed that one of the de novo GARS1 variants results in a loss-of-function effect, consistent with other pathogenic GARS1 alleles. In sum, the patients' clinical presentation, assessments of previously identified GARS1 variants and functional assays in yeast suggest that the GARS1 variants described here cause iSMA. GARS1 variants have been previously associated with Charcot-Marie-Tooth disease (CMT2D) and distal SMA type V (dSMAV). Our findings expand the allelic heterogeneity of GARS-associated disease and support that severe early-onset SMA can be caused by variants in this gene. Distinguishing the SMA phenotype caused by SMN1 variants from that due to pathogenic variants in other genes such as GARS1 significantly alters approaches to treatment.

Loss of BICD2 in muscle drives motor neuron loss in a developmental form of spinal muscular atrophy

Autosomal dominant missense mutations in BICD2 cause Spinal Muscular Atrophy Lower Extremity Predominant 2 (SMALED2), a developmental disease of motor neurons. BICD2 is a key component of the cytoplasmic dynein/dynactin motor complex, which in axons drives the microtubule-dependent retrograde transport of intracellular cargo towards the cell soma. Patients with pathological mutations in BICD2 develop malformations of cortical and cerebellar development similar to Bicd2 knockout (-/-) mice. In this study we sought to re-examine the motor neuron phenotype of conditional Bicd2-/- mice. Bicd2-/- mice show a significant reduction in the number of large calibre motor neurons of the L4 ventral root compared to wild type mice. Muscle-specific knockout of Bicd2 results in a similar reduction in L4 ventral axons comparable to global Bicd2-/- mice. Rab6, a small GTPase required for the sorting of exocytic vesicles from the Trans Golgi Network to the plasma membrane is a major binding partner of BICD2. We therefore examined the secretory pathway in SMALED2 patient fibroblasts and demonstrated that BICD2 is required for physiological flow of constitutive secretory cargoes from the Trans Golgi Network to the plasma membrane using a VSV-G reporter assay. Together, these data indicate that BICD2 loss from muscles is a major driver of non-cell autonomous pathology in the motor nervous system, which has important implications for future therapeutic approaches in SMALED2.

[Spinal muscular atrophy : Time for newborn screening?]

The most common neurodegenerative disease in childhood is spinal muscular atrophy (SMA). The severe infantile type 1 (Werdnig-Hoffman disease) makes 60% of SMA in total. These children usually die within 18 months without ventilation. New therapeutic approaches have led from the theoretical concept to randomized controlled clinical trials in patients. For the first time, a pharmacological treatment of SMA has been approved. The early detection of the disease is decisive for the success of therapy. All previous data suggest starting treatment early and when possible prior to the onset of symptoms considerably improves the outcome in comparison to a delayed start. The goal must be the presymptomatic diagnosis in order to initiate treatment before motor neuron degeneration. Technical and ethical prerequisites for a molecular genetic newborn screening are given.

SMA Diagnosis: Detection of SMN1 Deletion with Real-Time mCOP-PCR System Using Fresh Blood DNA

BACKGROUND

Spinal muscular atrophy (SMA) is one of the most common autosomal recessive disorders. The symptoms are caused by defects of lower motor neurons in the spinal cord. More than 95% of SMA patients are homozygous for survival motor neuron 1 (SMN1) deletion. We previously developed a screening system for SMN1 deletion based on a modified competitive oligonucleotide priming-PCR (mCOP-PCR) technique using dried blood spot (DBS) on filter paper. This system is convenient for mass screening in the large population and/or first-tier diagnostic method of the patients in the remote areas. However, this system was still time-consuming and effort-taking, because it required pre-amplification procedure to avoid non-specific amplification and gel-electrophoresis to detect the presence or absence of SMN1 deletion. When the fresh blood samples are used instead of DBS, or when the gel-electrophoresis is replaced by real-time PCR, we may have a simpler and more rapid diagnostic method for SMA.

AIM

To establish a simpler and more rapid diagnostic method of SMN1 deletion using fresh blood DNA.

METHODS

DNA samples extracted from fresh blood and stored at 4 ℃ for 1 month. The samples were assayed using a real-time mCOP-PCR system without pre-amplification procedures. DNA samples had already been genotyped by PCR-restriction fragment length polymorphism (PCR-RFLP), showing the presence or absence of SMN1 exon 7. The DNA samples were directly subjected to the mCOP-PCR step. The amplification of mCOP-PCR was monitored in a real-time PCR apparatus.

RESULTS

The genotyping results of the real-time mCOP-PCR system using fresh blood DNA were completely matched with those of PCR-RFLP. In this real-time mCOP-PCR system using fresh blood-DNA, it took only four hours from extraction of DNA to detection of the presence or absence of SMN1 deletion, while it took more than 12 hours in PCR-RFLP.

CONCLUSION

Our real-time mCOP-PCR system using fresh blood DNA was rapid and accurate, suggesting it may be useful for the first-tier diagnostic method of SMA.

Single-Dose Gene-Replacement Therapy for Spinal Muscular Atrophy

BACKGROUND

Spinal muscular atrophy type 1 (SMA1) is a progressive, monogenic motor neuron disease with an onset during infancy that results in failure to achieve motor milestones and in death or the need for mechanical ventilation by 2 years of age. We studied functional replacement of the mutated gene encoding survival motor neuron 1 (SMN1) in this disease.

METHODS

Fifteen patients with SMA1 received a single dose of intravenous adeno-associated virus serotype 9 carrying SMN complementary DNA encoding the missing SMN protein. Three of the patients received a low dose (6.7×10¹³ vg per kilogram of body weight), and 12 received a high dose (2.0×10¹⁴ vg per kilogram). The primary outcome was safety. The secondary outcome was the time until death or the need for permanent ventilatory assistance. In exploratory analyses, we compared scores on the CHOP INTEND (Children's Hospital of Philadelphia Infant Test of Neuromuscular Disorders) scale of motor function (ranging from 0 to 64, with higher scores indicating better function) in the two cohorts and motor milestones in the high-dose cohort with scores in studies of the natural history of the disease (historical cohorts).

RESULTS

As of the data cutoff on August 7, 2017, all 15 patients were alive and event-free at 20 months of age, as compared with a rate of survival of 8% in a historical cohort. In the high-dose cohort, a rapid increase from baseline in the score on the CHOP INTEND scale followed gene delivery, with an increase of 9.8 points at 1 month and 15.4 points at 3 months, as compared with a decline in this score in a historical cohort. Of the 12 patients who had received the high dose, 11 sat unassisted, 9 rolled over, 11 fed orally and could speak, and 2 walked independently. Elevated serum aminotransferase levels occurred in 4 patients and were attenuated by prednisolone.

CONCLUSIONS

In patients with SMA1, a single intravenous infusion of adeno-associated viral vector containing DNA coding for SMN resulted in longer survival, superior achievement of motor milestones, and better motor function than in historical cohorts. Further studies are necessary to confirm the safety and efficacy of this gene therapy. (Funded by AveXis and others; ClinicalTrials.gov number, NCT02122952 .).

Nusinersen versus Sham Control in Infantile-Onset Spinal Muscular Atrophy

BACKGROUND

Spinal muscular atrophy is an autosomal recessive neuromuscular disorder that is caused by an insufficient level of survival motor neuron (SMN) protein. Nusinersen is an antisense oligonucleotide drug that modifies pre-messenger RNA splicing of the SMN2 gene and thus promotes increased production of full-length SMN protein.

METHODS

We conducted a randomized, double-blind, sham-controlled, phase 3 efficacy and safety trial of nusinersen in infants with spinal muscular atrophy. The primary end points were a motor-milestone response (defined according to results on the Hammersmith Infant Neurological Examination) and event-free survival (time to death or the use of permanent assisted ventilation). Secondary end points included overall survival and subgroup analyses of event-free survival according to disease duration at screening. Only the first primary end point was tested in a prespecified interim analysis. To control the overall type I error rate at 0.05, a hierarchical testing strategy was used for the second primary end point and the secondary end points in the final analysis.

RESULTS

In the interim analysis, a significantly higher percentage of infants in the nusinersen group than in the control group had a motor-milestone response (21 of 51 infants [41%] vs. 0 of 27 [0%], P<0.001), and this result prompted early termination of the trial. In the final analysis, a significantly higher percentage of infants in the nusinersen group than in the control group had a motor-milestone response (37 of 73 infants [51%] vs. 0 of 37 [0%]), and the likelihood of event-free survival was higher in the nusinersen group than in the control group (hazard ratio for death or the use of permanent assisted ventilation, 0.53; P=0.005). The likelihood of overall survival was higher in the nusinersen group than in the control group (hazard ratio for death, 0.37; P=0.004), and infants with a shorter disease duration at screening were more likely than those with a longer disease duration to benefit from nusinersen. The incidence and severity of adverse events were similar in the two groups.

CONCLUSIONS

Among infants with spinal muscular atrophy, those who received nusinersen were more likely to be alive and have improvements in motor function than those in the control group. Early treatment may be necessary to maximize the benefit of the drug. (Funded by Biogen and Ionis Pharmaceuticals; ENDEAR ClinicalTrials.gov number, NCT02193074 .).

Relationships between long-term observations of motor milestones and genotype analysis results in childhood-onset Japanese spinal muscular atrophy patients

AIM

To clarify the long-term natural history of SMA in Japanese patients by investigating the peak motor milestones of cases 7months through 57years of age, in efforts to contribute to evaluating outcomes of new therapeutic interventions.

METHODS

We sub-classified 112 SMA type I-III cases into type Ia, type Ib, type IIa, type IIb, type IIIa and type IIIb, according to peak motor milestone achieved, and analyzed the SMN1, SMN2 and NAIP genes in relation to clinical subtypes.

RESULTS

In type I cases, there was a significant difference (p<0.0001), depending on whether or not head control was obtained, in the time of ventilation support being required. In type II cases as well, the time at which the ability to maintain the sitting position independently was lost also differed significantly (p<0.01) between those acquiring the ability to sit unaided within eight months after birth and those acquiring this ability after eight months of age. In type III cases, being able versus unable to climb stairs was associated with a significant difference (p=0.02) in the median time until loss of walking independently. Positive correlations were also seen between copy numbers and the clinical severity of SMA.

CONCLUSION

Our long-term results show peak motor milestone evaluations distinguishing between subtypes to be useful not only as outcome measures for assessing treatment efficacy in clinical trials but also for predicting the clinical courses of Japanese SMA patients.

New, Improved Version of the mCOP-PCR Screening System for Detection of Spinal Muscular Atrophy Gene (SMN1) Deletion

BACKGROUND

Spinal muscular atrophy (SMA) is a frequent autosomal recessive disorder, characterized by lower motor neuron loss in the spinal cord. More than 95% of SMA patients show homozygous survival motor neuron 1 (SMN1) deletion. We previously developed a screening system for SMN1 deletion based on a modified competitive oligonucleotide priming-PCR (mCOP-PCR) technique. However, non-specific amplification products were observed with mCOP-PCR, which might lead to erroneous interpretation of the screening results.

AIM

To establish an improved version of the mCOP-PCR screening system without non-specific amplification.

METHODS

DNA samples were assayed using a new version of the mCOP-PCR screening system. DNA samples had already been genotyped by PCR-restriction fragment length polymorphism (PCR-RFLP), showing the presence or absence of SMN1 exon 7. The new mCOP-PCR method contained a targeted pre-amplification step of the region, including an SMN1-specific nucleotide, prior to the mCOP-PCR step. mCOP-PCR products were electrophoresed on agarose gels.

RESULTS

No non-specific amplification products were detected in electrophoresis gels with the new mCOP-PCR screening system.

CONCLUSION

An additional targeted pre-amplification step eliminated non-specific amplification from mCOP-PCR screening.

[Possible treatments for infantile spinal atrophy]

The new treatments of spinal muscular atrophy (SMA) due by SMN1 gene deletions are reviewed. There are several ways to increase the protein SMN, its activity and persistence in the tissues. Neuroprotective drugs as olesoxime or riluzole, and drugs acting by epigenetic mechanisms, as histone deacetylase inhibitors, have shown positive effects in preclinical studies but no clear efficacy in clinical trials. They might give in the future added benefits when used associated to other genetic modifying drugs. The best improvements in murine models of SMA and in clinical trials have been reached with antisense oligonucleotides, drugs that modify the splicing of SMN2, and they are expected to get better in the near future. Nusinersen, a methoxi-ethyl phosphotioate antisense oligonucleotide has recently approved for treatment of patients with SMA type 1 after having proved its efficacy in clinical trial phase 3. The results of nusinersen are reviewed. New modifications of antisense oligonucleotides with better access to brain, spinal cord and peripheral tissues are on the way. There are data of the efficacy of the genetic therapy with SMN1 gene through adenoassociated virus, now in phase 1 trial. A constant feature of these new treatments is that the earlier the treatment, the best are the results, and they are even better in presymptomatic stage. The general standards of care, particularly nutrition and respiratory management are needed in order to reach optimal results with the new therapies.

Hyperleptinemia in children with autosomal recessive spinal muscular atrophy type I-III

Background

Autosomal-recessive proximal spinal muscular atrophies (SMA) are disorders characterized by a ubiquitous deficiency of the survival of motor neuron protein that leads to a multisystemic disorder, which mostly affects alpha motor neurons. Disease progression is clinically associated with failure to thrive or weight loss, mainly caused by chewing and swallowing difficulties. Although pancreatic involvement has been described in animal models, systematic endocrinological evaluation of the energy metabolism in humans is lacking.

Methods

In 43 patients with SMA type I-III (8 type I; 22 type II; 13 type III), aged 0.6–21.8 years, auxological parameters, pubertal stage, motor function (Motor Function Measurement 32 –MFM32) as well as levels of leptin, insulin glucose, hemoglobin A1c, Homeostasis Model Assessment index and an urinary steroid profile were determined.

Results

Hyperleptinemia was found in 15/35 (43%) of our patients; 9/15 (60%) of the hyperleptinemic patients were underweight, whereas 1/15 (7%) was obese. Hyperleptinemia was associated with SMA type (p = 0.018). There was a significant association with decreased motor function (MFM32 total score in hyperleptinemia 28.5%, in normoleptinemia 54.7% p = 0.008, OR 0.969; 95%-CI: 0.946–0.992). In addition, a higher occurrence of hirsutism, premature pubarche and a higher variability of the urinary steroid pattern were found.

Conclusion

Hyperleptinemia is highly prevalent in underweight children with SMA and is associated with disease severity and decreased motor function. Neuronal degradation of hypothalamic cells or an increase in fat content by muscle remodeling could be the cause of hyperleptinemia.

Diverse role of survival motor neuron protein

The multifunctional Survival Motor Neuron (SMN) protein is required for the survival of all organisms of the animal kingdom. SMN impacts various aspects of RNA metabolism through the formation and/or interaction with ribonucleoprotein (RNP) complexes. SMN regulates biogenesis of small nuclear RNPs, small nucleolar RNPs, small Cajal body-associated RNPs, signal recognition particles and telomerase. SMN also plays an important role in DNA repair, transcription, pre-mRNA splicing, histone mRNA processing, translation, selenoprotein synthesis, macromolecular trafficking, stress granule formation, cell signaling and cytoskeleton maintenance. The tissue-specific requirement of SMN is dictated by the variety and the abundance of its interacting partners. Reduced expression of SMN causes spinal muscular atrophy (SMA), a leading genetic cause of infant mortality. SMA displays a broad spectrum ranging from embryonic lethality to an adult onset. Aberrant expression and/or localization of SMN has also been associated with male infertility, inclusion body myositis, amyotrophic lateral sclerosis and osteoarthritis. This review provides a summary of various SMN functions with implications to a better understanding of SMA and other pathological conditions.

A rare variant (c.863G>T) in exon 7 of SMN1 disrupts mRNA splicing and is responsible for spinal muscular atrophy

Proximal spinal muscular atrophy (SMA) is an autosomal recessive neuromuscular disorder caused by deletion or mutation of SMN1 (survival motor neuron 1). SMN exon 7 splicing is regulated by a number of exonic and intronic regulatory sequences and the trans-factors that bind them. Variants located in or near these regulated regions should be evaluated to determine their effect on splicing. We identified the rare variant c.863G>T (r.835_*3del, p.Gly279Glufs*5) in exon 7 of SMN1 in three patients affected with type I or type II SMA. Most of the SMN1 transcripts exhibited complete loss of exon 7 in vivo. The ex vivo splicing assay demonstrated that the variant disrupts inclusion of exon 7 (~85%) in the SMN1 mRNA; replacement with various bases yielded a variety of splicing effects in SMN1 and SMN2 pre-mRNA. The c.863G>T (r.835_*3del, p.Gly279Glufs*5) variant is located in a region that includes binding sites for multiple splicing factors including Tra2β1. Thus, the variant disrupts Tra2β1 binding, but does not affect binding of hnRNP A1. These findings demonstrate how rare variants influence pre-mRNA splicing of SMN and reveal the functional influence of c.863G>T (r.835_*3del, p.Gly279Glufs*5) variant in patients with SMA.

Distally pronounced infantile spinal muscular atrophy with severe axonal and demyelinating neuropathy associated with the S230L mutation of SMN1

Two Croatian siblings with atypical clinical findings in the presence of SMN1 gene mutations are reported. The girl presented with delayed motor development and weakness in hands and feet in her first year of life. She never stood or walked and developed scoliosis and joint contractures during childhood. Her hands and feet were non-functional when last seen at age 14 years. Her 4-year-old brother was more severely affected and had a clinical picture resembling infantile spinal muscular atrophy (SMA) type 1. He also showed unusual distally pronounced weakness and facial weakness. Both patients had no sensory deficits but gave evidence of a mixed axonal and demyelinating neuropathy with pronounced slowing in the distal nerve segments. Unexpectedly, both siblings showed a compound heterozygous SMN1 mutation (heterozygous deletion and missense mutation c.689C > T; p.S230L), thus confirming infantile SMA. In addition, next generation sequencing of 52 genes for hereditary neuropathies revealed a heterozygous missense mutation c.505T > C; p.Y169H in the SH3TC2 gene that was transmitted by the healthy father. Our observations widen the phenotypic consequences of SMN1 gene mutations and support the notion to look for additional genetic factors which may modify the clinical picture in atypical cases.

Establishment of Homozygote Mutant Human Embryonic Stem Cells by Parthenogenesis

We report on the derivation of a diploid 46(XX) human embryonic stem cell (HESC) line that is homozygous for the common deletion associated with Spinal muscular atrophy type 1 (SMA) from a pathenogenetic embryo. By characterizing the methylation status of three different imprinted loci (MEST, SNRPN and H19), monitoring the expression of two parentally imprinted genes (SNRPN and H19) and carrying out genome-wide SNP analysis, we provide evidence that this cell line was established from the activation of a mutant oocyte by diploidization of the entire genome. Therefore, our SMA parthenogenetic HESC (pHESC) line provides a proof-of-principle for the establishment of diseased HESC lines without the need for gene manipulation. As mutant oocytes are easily obtained and readily available during preimplantation genetic diagnosis (PGD) cycles, this approach should provide a powerful tool for disease modelling and is especially advantageous since it can be used to induce large or complex mutations in HESCs, including gross DNA alterations and chromosomal rearrangements, which are otherwise hard to achieve.

[SMN1 Gene Point Mutations in Type I-IV Proximal Spinal Muscular Atrophy Patients with a Single Copy of SMN1]

Type I-IV proximal spinal muscular atrophy (SMA) is one of the most common autosomal-recessive diseas- es, which are characterized in the majority of cases by a severely disabling course. Proximal SMA results from mutations in the telomeric copy of SMN-SMN1 gene. Major SMN1 gene mutation types are deletions in the exons 7 and/or 8, which were revealed to be in the homozygous state in 95% of patients. Deletions in the in- dicated exons of SMN1 gene were revealed in a compound-heterozygous state in combination with intragenic point mutations in the remainder 5% of proximal SMA cases. In the present study, we conducted an analysis of point mutations in eight patients with type I-III proximal SMA phenotype, which had a deletion in 7-8- exons of SMN1 gene in the heterozygous state. We revealed seven different mutations, two of which (c.824G > C (p.Gly275A1a) and c.825-2A > T) are described here for the first time. In addition, mutation c.824G > C (p.Gly275A1a) was observed twice in the examined sample. In seven cases a heterozygous carrier of point mutations was one of the parents of the affected children (in six cases, the father; in one case, the mother). Only one mutation, c.43C > T (p.Gln15X), emerged de novo in a genital cell of the child's father.

Methylation levels of SLC23A2 and NCOR2 genes correlate with spinal muscular atrophy severity

Spinal muscular atrophy (SMA) is a monogenic neurodegenerative disorder subdivided into four different types. Whole genome methylation analysis revealed 40 CpG sites associated with genes that are significantly differentially methylated between SMA patients and healthy individuals of the same age. To investigate the contribution of methylation changes to SMA severity, we compared the methylation level of found CpG sites, designed as "targets", as well as the nearest CpG sites in regulatory regions of ARHGAP22, CDK2AP1, CHML, NCOR2, SLC23A2 and RPL9 in three groups of SMA patients. Of notable interest, compared to type I SMA male patients, the methylation level of a target CpG site and one nearby CpG site belonging to the 5'UTR of SLC23A2 were significantly hypomethylated 19-22% in type III-IV patients. In contrast to type I SMA male patients, type III-IV patients demonstrated a 16% decrease in the methylation levels of a target CpG site, belonging to the 5'UTR of NCOR2. To conclude, this study validates the data of our previous study and confirms significant methylation changes in the SLC23A2 and NCOR2 regulatory regions correlates with SMA severity.

[Two cases of a proximal spinal muscular atrophy (Werdnig-Hoffmann's disease) in one family]

A short review of literature data on the pathogenesis and clinical presentations of spinal muscular atrophies is provided. We report two cases of Werdnig-Hoffmann's disease in one family and present a diagnostic search strategy which allows the ordinary neurologist to distinguish this pathology.

Mutation in E1, the ubiquitin activating enzyme, reduces Drosophila lifespan and results in motor impairment

Neurodegenerative diseases cause tremendous suffering for those afflicted and their families. Many of these diseases involve accumulation of mis-folded or aggregated proteins thought to play a causal role in disease pathology. Ubiquitinated proteins are often found in these protein aggregates, and the aggregates themselves have been shown to inhibit the activity of the proteasome. These and other alterations in the Ubiquitin Pathway observed in neurodegenerative diseases have led to the question of whether impairment of the Ubiquitin Pathway on its own can increase mortality or if ongoing neurodegeneration alters Ubiquitin Pathway function as a side-effect. To address the role of the Ubiquitin Pathway in vivo, we studied loss-of-function mutations in the Drosophila Ubiquitin Activating Enzyme, Uba1 or E1, the most upstream enzyme in the Ubiquitin Pathway. Loss of only one functional copy of E1 caused a significant reduction in adult lifespan. Rare homozygous hypomorphic E1 mutants reached adulthood. These mutants exhibited further reduced lifespan and showed inappropriate Ras activation in the brain. Removing just one functional copy of Ras restored the lifespan of heterozygous E1 mutants to that of wild-type flies and increased the survival of homozygous E1 mutants. E1 homozygous mutants also showed severe motor impairment. Our findings suggest that processes that impair the Ubiquitin Pathway are sufficient to cause early mortality. Reduced lifespan and motor impairment are seen in the human disease X-linked Infantile Spinal Muscular Atrophy, which is associated with mutation in human E1 warranting further analysis of these mutants as a potential animal model for study of this disease.

Prospective cohort study of spinal muscular atrophy types 2 and 3

OBJECTIVE

To characterize the natural history of spinal muscular atrophy type 2 and type 3 (SMA 2/3) beyond 1 year and to report data on clinical and biological outcomes for use in trial planning.

METHODS

We conducted a prospective observational cohort study of 79 children and young adults with SMA 2/3 who participated in evaluations for up to 48 months. Clinically, we evaluated motor and pulmonary function, quality of life, and muscle strength. We also measured SMN2 copy number, hematologic and biochemical profiles, muscle mass by dual x-ray absorptiometry (DXA), and the compound motor action potential (CMAP) in a hand muscle. Data were analyzed for associations between clinical and biological/laboratory characteristics cross-sectionally, and for change over time in outcomes using all available data.

RESULTS

In cross-sectional analyses, certain biological measures (specifically, CMAP, DXA fat-free mass index, and SMN2 copy number) and muscle strength measures were associated with motor function. Motor and pulmonary function declined over time, particularly at time points beyond 12 months of follow-up.

CONCLUSION

The intermediate and mild phenotypes of SMA show slow functional declines when observation periods exceed 1 year. Whole body muscle mass, hand muscle compound motor action potentials, and muscle strength are associated with clinical measures of motor function. The data from this study will be useful for clinical trial planning and suggest that CMAP and DXA warrant further evaluation as potential biomarkers.

Neurogenic muscle hypertrophy in type III spinal muscular atrophy

Neurogenic muscle hypertrophy is very unusual and has been rarely described. We described a 25-year-old woman presented with proximal muscle weakness with calf muscle hypertrophy. Limb magnetic resonance imaging scans showed increased muscle bulk without fatty changes, and a muscle biopsy revealed prominent hypertrophic type II muscle fibers. A mutation in SMN1 was found in a genetic analysis. This is the first report of neurogenic muscle hypertrophy seen in genetically confirmed spinal muscular atrophy III.

Impaired minor tri-snRNP assembly generates differential splicing defects of U12-type introns in lymphoblasts derived from a type I SMA patient

The survival of motor neuron (SMN) protein is essential for cytoplasmic assembly of spliceosomal snRNPs. Although the normal proportion of endogenous snRNAs is unevenly altered in spinal muscular atrophy (SMA) tissues, the biogenesis of individual snRNPs is not dramatically affected in SMN-deficient cells. The SMN protein is also required for normal Cajal body (CB) formation, but the functional consequences of CB disruption upon SMN deficiency have not yet been analyzed at the level of macromolecular snRNPs assembly. Here, we show that the SMN protein is required for tri-snRNPs formation and that the level of the minor U4atac/U6atac/U5 tri-snRNPs is dramatically decreased in lymphoblasts derived from a patient suffering from a severe form of SMA. We found also that splicing of some, but not all, minor introns is inhibited in these cells, demonstrating links between SMN deficiency and differential alterations of splicing events mediated by the minor spliceosome. Our results suggest that SMA might result from the inefficient splicing of one or only a few pre-mRNAs carrying minor introns and coding for proteins required for motor neurons function and/or organization.

[Quantitative analysis of the genes determining spinal muscular atrophy]

Spinal muscular atrophy (SMA) is one of the most common autosomal recessive diseases, affecting approximately one in 10,000 live births and with a carrier frequency of approximately one in 35. The disease is caused by a deficiency of the ubiquitous protein survival of motor neuron (SMN), which is encoded by the SMN1 and SMN2 genes. Due to a single nucleotide polymorphism in exon 7, SMN2 produces less full-length transcript than SMN1 and cannot prevent neuronal cell death at physiologic gene dosages. On the other hand, the copy number of SMN2 affects the amount of SMN protein produced and the severity of the SMA phenotype. SMN gene dosage analysis can determine the copy number of SMN1 to detect carriers and patients heterozygous for the absence of SMN1 exon 7. This study provides copy number estimation of SMN1 gene by real-time PCR technique in 56 SMA type I., II., III. patients, 159 parents and healthy relatives and in 152 undefined SMA patients. Among the family members, 91 carriers have been detected and in 56 patients homozygous deletion of SMN1 exon 7 has been confirmed. Moreover, in 12 patients compound heterozygosity of SMN1 exon 7 mutation has been detected, thus providing the possible diagnosis of SMA. In 94 patients, copy number of SMN2 has also been evaluated and a good correlation has been found with the phenotype of the disease. Due to the genetic complexity and the high carrier frequency, accurate risk assessment and genetic counselling are particularly important for the families. These new results provide improvement of the diagnostic service in SMA in Hungary with focus on proper genetic counselling and possible enrolment of the patients in future therapeutic interventions.

Devastation of bone tissue in the appendicular skeleton parallels the progression of neuromuscular disease

A mouse model of spinal muscular atrophy with respiratory distress (SMARD1) was used to study the consequences of neuromuscular degenerative disease on bone quantity and morphology. Histomorphometry and micro-computed tomography were used to assess the cortical and cancellous bone in the tibia, femur and humerus of adult neuromuscular degeneration (nmd) mice (up to 21w) and age-matched wild-type controls (WT). At 21w, the average lengths of the humerus, tibia and femur were 15%, 10%, and 10% shorter in the nmd mice, respectively. The midshaft of the humerus, tibia and femur of nmd mice had 41%, 47% and 34% less cortical bone than the WT. In the humeral, tibial, and femoral metaphyses of the nmd mice, there was 50%, 78%, and 85% less trabecular bone volume, and 58%, 92%, and 94% less trabecular connectivity than the WT. NMD cortical bone had less than half of the 42% active surface measured in the WT, yet the mineral apposition rate of those surfaces were similar between strains (nmd: 1.80 microm x day(-1); WT: 2.05 microm x day(-1)). Osteoclast number and activity levels did not differ across strains. These data emphasize that neuromuscular degeneration as a result of immunoglobulin S-mu binding protein-2 (Ighmbp2) mutation will compromise several critical parameters of bone quantity and architecture, the most severe occurring in the trabecular compartment.

A population-based study of genotypic and phenotypic variability in children with spinal muscular atrophy

AIMS

To describe the occurrence of spinal muscular atrophy (SMA) in childhood; to evaluate if any of the genes in the SMA region on chromosome 5q13 correlates with disease severity; to make genotype-phenotype correlations; to evaluate the variability of different disease alleles in carriers and the sensitivity of multiplex ligation-dependent probe amplification (MLPA) for detecting carriers.

METHODS

In a population-based study from Western Sweden MLPA was used to determine the copy-numbers of several genes in the SMA region (SMN1, SMN2, BIRC1, GTF2H2 and SERF1A) in SMA-patients and their parents.

RESULTS

We estimated the incidence of SMN1-related SMA in childhood at 1 in 11 800 live births and confirmed the relationship between the number of SMN2 copies and the severity of disease. No other direct relationships were found. All but one of the analysed parents were confirmed as carriers by MLPA analysis. A total of at least 30 different disease alleles were identified and no specific disease allele represented more than 15% of the total.

CONCLUSION

The childhood incidence of SMA in the Swedish population is around 1 in 12,000 live births and it is unlikely that there is any founder effect involved in SMA in western Sweden.

Werdnig-Hoffmann disease: report of the first case clinically identified and genetically confirmed in central Africa (Kinshasa-Congo)

Werdnig-Hoffmann Disease: Report of the first case clinically identified and genetically confirmed in Central Africa (Kinshasa-Congo): Type 1 spinal muscular atrophy (SMA1) or Werdnig-Hoffman disease is rarely described in black populations. We report on one black patient diagnosed in Kinshasa. This patient was referred to Paediatric consultation at the age of 5 months 1/2 with extreme hypotonia progressing since birth, severe muscular weakness in his trunk and proximal parts of the extremities, ASD type II, and repeated episodes of pulmonary infections. He died of severe respiratory failure at the age of 10 months. EMG analysis revealed motor neuron a defect without nerve conduction anomaly, suggesting the diagnosis of spinal muscular atrophy disease. The diagnosis of SMA1 was definitely confirmed by a quantitative PCR-based testing that demonstrated homozygous deletion of SMN1, the primary disease-causing gene for spinal muscular atrophy, while two normal SMN2 alleles were present. There was a history of similar clinical symptomatology in a patient's older brother, suggesting a familial involvement. To the best of our knowledge, this is the first documented Werdnig-Hoffman case ever reported from Central Africa people.

[Molecular diagnosis of spinal muscular atrophy by multiplex ligation-dependent probe amplification]

OBJECTIVE

To investigate the effect of multiplex ligation-dependent probe amplification (MLPA) in molecular diagnosis of spinal muscular atrophy (SMA).

METHODS

Peripheral blood samples were collected from 13 SMA patients, 31 parents of SMA patients, 50 healthy individuals without family history of SMA, and 10 specimens of amniotic fluid from these families were collected too. Genomic DNA was analyzed by MLPA, conventional PCR-RFLP, and allele-specific PCR.

RESULTS

In complete agreement with the results of conventional PCR-RFLP and allele-specific PCR, MLPA analysis showed that all of the 13 patients had homozygous deletion of the survival of motor neuron 1 (SMN1) gene, and there was significant difference between the SMA severity (type I to type III) and SMN2 copy number (P < 0.05). Of the 31 parents 29 (93.5%) had 1 copy of SMN1, 2 (6.5%) had 2 copies of SMN1. Of the 50 healthy individuals, 1 (2.0%) had 1 copy of SMN1, 48 (96.0%) had 2 copies of SMN1, and 1 (2.0%) had 3 copies. The SMN1 copy number of the parents was significantly higher than that of the healthy individuals (P < 0.01). Two of the 10 fetuses had homozygous deletion of SMN1.

CONCLUSION

The MLPA technique has proved to be an accurate and reliable tool for the molecular diagnosis of SMA, both in patients and in healthy carriers.