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PubMed2001

A direct interaction between the survival motor neuron protein and p53 and its relationship to spinal muscular atrophy.

Mutations in the SMN1 (survival motor neuron 1) gene cause spinal muscular atrophy (SMA). We now show that SMN protein, the SMN1 gene product, interacts directly with the tumor suppressor protein, p53. Pathogenic missense mutations in SMN reduce both self-association and p53 binding by SMN, and the extent of the reductions correlate with disease severity. The inactive, truncated form of SMN produced by the SMN2 gene in SMA patients fails to bind p53 efficiently. SMN and p53 co-localize in nuclear Cajal bodies, but p53 redistributes to the nucleolus in fibroblasts from SMA patients. These results suggest a functional interaction between SMN and p53, and the potential for apoptosis when this interaction is impaired may explain motor neuron death in SMA.

Apoptosis↗
PubMed2006

Detection of spinal muscular atrophy carriers by nested polymerase chain reaction of single sperm cells.

Spinal muscular atrophy (SMA) is an autosomal recessive disorder with a carrier frequency of approximately 1 in 40. Approximately 95% of patients have homozygous deletions of exon 7 and/or 8 of the SMN1 gene. Carrier testing for SMA is relatively complex and requires quantitative polymerase chain reaction (PCR) of genomic DNA to determine SMN1 copy number. The purpose of this study was to assess the feasibility of carrier testing for SMA in males, by nested PCR analysis of SMN1 deletions in single sperm cells. A nested PCR method was developed to amplify SMN1 exon 7 in single cells. Restriction enzyme digestion with DraI was used to differentiate between the highly homologous SMN1 and SMN2 genes. Single sperm cells from five known SMA carriers and six noncarriers were analyzed. Among the five carriers, a total of 132 single sperm cells were analyzed and SMN1 exon 7 deletion was detected in 68 cells (51.5%). In contrast, among the six noncarriers, a total of 136 single sperm cells were analyzed. Of these, an apparent SMN1 exon 7 deletion was detected in four sperm cells. This was interpreted as an allele dropout (ADO) rate of 2.9%. We conclude that nested PCR of SMN1 exon 7 is an accurate and reproducible method for detection of SMA male carriers with a SMN1 deletion.

Base Sequence↗
PubMed1994

Survival of individuals with spinal muscular atrophy on ventilatory support.

Six ventilator-assisted individuals (VAIs) with spinal muscular atrophy (SMA) are described. All six survived by using intermittent positive pressure ventilation via an indwelling tracheostomy for a mean of 11.7 +/- 17.7 yr despite frequent episodes of mucus plugging and pneumonia. Four of the VAIs also received all nutrition via indwelling gastrostomy tubes because of severe bulbar muscle weakness. Four VAIs used tracheostomy intermittent positive pressure ventilation with their tracheostomy cuffs deflated and could communicate verbally. Five of the six VAIs remained institutionalized from the onset of ventilatory use. Two SMA VAIs survived for 15 and 4 yr, respectively, despite need for ventilatory support since early infancy. All four SMA VAIs who could communicate remained socially active and one, gainfully employed. We conclude that for patients with advanced SMA markedly prolonged survival is possible with ventilatory assistance despite severe respiratory and bulbar muscle dysfunction.

Activities of Daily Living↗
PubMed2005

Operative treatment for hip subluxation in spinal muscular atrophy.

Subluxation of the hip is common in patients with intermediate spinal muscular atrophy. This retrospective study aimed to investigate the influence of surgery on pain and function, as well as the natural history of subluxed hips which were treated conservatively. Thirty patients were assessed clinically and radiologically. Of the nine who underwent surgery only one reported satisfaction and four had recurrent subluxation. Of the 21 patients who had no surgery, 18 had subluxation at the latest follow-up, but only one reported pain in the hip. We conclude that surgery for subluxation of the hip in these patients is not justified.

Adolescent↗
PubMed1991

Linkage analysis in spinal muscular atrophy, by six closely flanking markers on chromosome 5.

The proximal spinal muscular atrophies (SMA) represent the second most common autosomal recessive disorder, after cystic fibrosis. The gene responsible for chronic SMA has recently been mapped to chromosome 5q by using genetic linkage studies. Among six markers mapping to this region, five were shown to be linked with the SMA locus in 39 chronic SMA families each containing at least two affected individuals. Multilocus analysis by the method of location score was used to establish the best estimate of the SMA gene location. Our data suggest that the most likely location for SMA is between loci D5S6 and D5S39. The genetic distances between these two markers are estimated to be 6.4 cM in males and 11.9 cM in females. Since meiosis were informative with D5S39 and D5S6 in 92% and 87% of SMA families, respectively, it is hoped that the present study will contribute to the calculation of genetic risk in SMA families.

Chromosome Mapping↗
PubMed2006

Spinal muscular atrophy: the RNP connection.

Degenerated motor neurons in the spinal cord are the pathological hallmark of spinal muscular atrophy (SMA). SMA is caused by mutations in the ubiquitously expressed survival motor neuron 1 (SMN1) gene, which lead to reduced levels of functional SMN protein. Many different functions have been assigned to SMN, including assembly of ribonucleoproteins (RNPs), splicing, transcription and axonal mRNA transport. Recently, tissue from SMA patients and animal models has been used to determine which function of SMN is affected in SMA patients. A surprising picture has emerged: the impaired assembly of RNP subunits of the spliceosome seems to be responsible for SMA pathogenesis. Here, we present a model of how this defect might cause motor-neuron degeneration and consider potential therapies.

Alternative Splicing↗
PubMed2002

A mouse model of spinal and bulbar muscular atrophy.

Spinal and bulbar muscular atrophy (SBMA) is an adult-onset motor neuron disease, caused by the expansion of a trinucleotide repeat (TNR) in exon 1 of the androgen receptor (AR) gene. This disorder is characterized by degeneration of motor and sensory neurons, proximal muscular atrophy, and endocrine abnormalities, such as gynecomastia and reduced fertility. We describe the development of a transgenic model of SBMA expressing a full-length human AR (hAR) cDNA carrying 65 (AR(65)) or 120 CAG repeats (AR(120)), with widespread expression driven by the cytomegalovirus promoter. Mice carrying the AR(120) transgene displayed behavioral and motor dysfunction, while mice carrying 65 CAG repeats showed a mild phenotype. Progressive muscle weakness and atrophy was observed in AR(120) mice and was associated with the loss of alpha-motor neurons in the spinal cord. There was no evidence of neurodegeneration in other brain structures. Motor dysfunction was observed in both male and female animals, showing that in SBMA the polyglutamine repeat expansion causes a dominant gain-of-function mutation in the AR. The male mice displayed a progressive reduction in sperm production consistent with testis defects reported in human patients. These mice represent the first model to reproduce the key features of SBMA, making them a useful resource for characterizing disease progression, and for testing therapeutic strategies for both polyglutamine and motor neuron diseases.

Animals↗
PubMed1976

A family of juvenile proximal spinal muscular atrophy with dominant inheritance.

A family with juvenile proximal spinal muscular atrophy with dominant inheritance and complete penetrance is reported. The disease occurred in three generations and showed high variations in the age of onset and progression among the affected members. A characteristic feature was the constant involvement of facial nuclei.

Adolescent↗
PubMed2026

Compound muscle action potential amplitudes in newborn screen positive spinal muscular atrophy.

OBJECTIVE: To evaluate the utility of compound muscle action potential (CMAP) amplitudes as biomarkers of disease severity in newborn screening (NBS)-positive infants with spinal muscular atrophy (SMA). METHODS: We conducted a retrospective review of 21 infants identified through SMA NBS (11 with 2 SMN2 copies and 10 with 3 SMN2 copies). Baseline and serial right median, ulnar, and fibular motor nerve CMAP amplitudes (millivolts, mV) were obtained during the study. Functional outcomes were assessed using the Children's Hospital of Philadelphia Infant Test of Neuromuscular Disorders (CHOP-INTEND). RESULTS: At baseline, infants with 2 SMN2 copies demonstrated significantly lower median, ulnar, and fibular CMAP amplitudes compared with infants with 3 SMN2 copies (p&#xa0;<&#xa0;0.05). In contrast, baseline CHOP-INTEND scores did not differ significantly between the two groups. Prior to genetic confirmation, a right median CMAP amplitude&#xa0;&#x2265;3.2&#xa0;mV predicted&#xa0;&#x2265;3 SMN2 copies. Following treatment, right median and fibular CMAP amplitudes demonstrated significant improvement over time, including in analyses accounting for SMN2 copies number. CONCLUSION: CMAP amplitudes obtained from multiple upper- and lower-extremity motor nerves provided objective electrophysiological measures that distinguished infants with two versus three SMN2 copies, despite similar baseline CHOP-INTEND scores. Furthermore, CMAP abnormalities were detectable in some cases before confirmatory genetic testing results became available. Serial CMAP measurements demonstrated significant longitudinal changes following treatment, whereas functional assessments approached ceiling values, supporting the potential value of electrophysiological monitoring in the era of disease-modifying therapies. SIGNIFICANCE: CMAP assessment is a useful adjunct in the evaluation of infants identified through SMA NBS.

Humans↗
PubMed1999

[Study of NAIP gene in spinal muscular atrophy].

OBJECTIVE: Investigating the correlation between the genotype and spinal muscular atrophy(SMA) clinical phenotype. METHODS: Neuronal apoptosis inhibitory protein(NAIP) gene analysis was performed by PCR amplification of exon 5 in 13 unrelated SMA patients with deletions of SMN gene. RESULTS: Two Type-I patients(2 M5, 40%) lacked the NAIP exon 5. CONCLUSION: The results suggest a possible correlation between NAIP gene deletion and the disease severity of SMA.

Child↗
PubMed2003

Spinal muscular atrophy type 1 quality of life.

OBJECTIVE: To compare healthcare professionals' assessment of the quality of life of spinal muscular atrophy type 1 children with that of the care providers for the children. DESIGN: The care providers of all 53 surviving spinal muscular atrophy type 1 children managed in one neuromuscular disease clinic were sent Likert-scale surveys of six quality of life issues and ten polar-adjective pairs. The quality of life estimations were compared with those of 67 clinicians and with those of 30 parents considering their unaffected children. RESULTS: One hundred care providers from 46 out of the 53 families (87%) responded. Although the clinicians' mean estimate of the children's quality of life was 2.85 +/- 0.2/10, the care providers' estimate was 7.81 +/- 0.2/10 (P < 0.0001). The care providers also found life with the children to be satisfying (6.0 +/- 0.2/7), interesting (6.6 +/- 0.1/7), friendly (6.1 +/- 0.1/7), enjoyable (6.3 +/- 0.1/7), worthwhile (6.7 +/- 0.1/7), full (6.6 +/- 0.1/7), hopeful (5.9 +/- 0.2/7), and rewarding (6.4 +/- 0.1/7), and they estimated the children to be happy (8.5 +/- 0.2/10) and their lives worth living (9.6 +/- 0.1/10). However, 69 of 104 felt that their lives were hard rather than easy, and 56 of 104 reported feeling tied down rather than free. Although the effort they felt for raising the child was high (8.3 +/- 0.3 by comparison with 5 for an unaffected child), the burden they felt in doing so was not (5.8 +/- 0.3/5). When asked whether they would or would not recommend ventilator use, 31 clinicians (45.5%) indicated they would, 24 (36.4%) would not, and 12 (18.2%) chose not to respond to this question. Care provider responses did not differ significantly from the responses of the parents of unaffected children except for the easy/hard semantic differential (care providers, 3.80 +/- 1.75 controls, 5.27 +/- 1.14, < 0.001). CONCLUSIONS: Although there is a widespread perception that spinal muscular atrophy type 1 children have a poor quality of life, this perception is not shared by their care providers.

Adult↗
PubMed1992

High-resolution genetic map around the spinal muscular atrophy (SMA) locus on chromosome 5.

Although autosomal recessive spinal muscular atrophy (SMA) has been mapped to chromosome 5q12-q13, there is for this region no genetic map based on highly informative markers. In this study we present the mapping of two previously reported microsatellite markers in 40 CEPH and 31 SMA pedigrees. We also describe the isolation of a new microsatellite marker at the D5S112 locus. The most likely order of markers (with recombination fractions given in parentheses) is 5cen-D5S6-(.02)-D5S125-(.04)-(JK53CA1/2,D5S11 2)-(.04)-D5S39-qter. The relative order of D5S6, D5S112, and D5S39 was confirmed by in situ hybridization. Multipoint linkage analysis in 31 SMA families indicates that the SMA locus lies in the 6-cM interval between D5S6 and JK53CA1/2, D5S112.

Base Sequence↗
PubMed1998

Treatment of type I spinal muscular atrophy with noninvasive ventilation and gastrostomy feeding.

Type I spinal muscular atrophy (SMA) is a rapidly progressive, degenerative neuromuscular disease of infancy. In severe SMA, weakness, hypotonia, and bulbar involvement lead to progressive respiratory insufficiency and swallowing dysfunction, which are frequently complicated by aspirations. There are few studies reported in the literature that address the respiratory management of type I SMA. This article reports the results of treating four patients with infantile SMA with noninvasive positive pressure ventilation and gastrostomy feeding. All patients had gastroesophageal reflux disease, which was managed medically. Despite these therapies, survival was only 1 to 3.5 months after presenting with severe aspirations. The treatment strategy, which can be effective in less rapidly progressive neuromuscular diseases, did not alter the very poor prognosis of type I SMA. The treatment options are reviewed, and a strategy designed to optimize quality of life for infants with this fatal disease is presented.

Deglutition Disorders↗
PubMedDate not supplied

Hip dislocation in patients with spinal muscular atrophy.

The propensity for hip dislocation in patients with spinal muscular atrophy (SMA) is well documented, but the appropriate treatment and even the long-term outcome of these hips in this patient population have not been well defined. The purpose of this study was to determine by long-term follow-up the natural history of dislocated hips in a cohort of SMA patients from a single institution. Pain and functional difficulties (positioning, skin and perineal care) were assessed and radiographs were reviewed in a total of 41 patients with a mean of 18 years of follow-up. Seventeen of 82 hips (21%) were dislocated in 14 patients and 20 hips were subluxed. Only two patients had any hip pain at follow-up, one had difficulty with seating, and no patients had difficulty with perineal care. Given the small number of patients with symptoms with dislocated hips, observation rather than surgical intervention seems warranted in SMA patients with hip dislocation.

Adolescent↗
PubMed1989

Scoliosis in spinal muscular atrophy: review of 63 cases.

We reviewed the incidence and severity of scoliosis in 37 patients with the intermediate type and 26 with the mild type of spinal muscular atrophy. In the intermediate type, scoliosis has an early onset and rapid progression before puberty, and a spinal fusion will be needed in virtually all cases. This rapid progression occurred despite routine use of a spinal brace. Hip dislocation was frequently present but, in most cases, was secondary to the pelvic tilt and did not contribute to the scoliosis. In the mild type, the scoliosis was more variable. In the 30% of patients who had scoliosis, progression was rapid during puberty but only in those who had lost ambulation. Of the four children with the intermediate type and the seven with the mild type who walked in light-weight orthoses, progression of scoliosis was slow, except in those who had lost ambulation. The ultimate effect of walking in orthoses is difficult to assess because of small numbers, but it seems to slow or at least delay progressive scoliosis.

Adolescent↗
PubMed2026

Molecular diagnosis of spinal muscular atrophy: Experience in a pediatric hospital in Argentina.

Introduction. Spinal muscular atrophy (SMA) is an autosomal recessive neuromuscular disease caused by the loss of the SMN1 gene, with a variable clinical spectrum determined primarily by the number of copies of the SMN2 gene. The development of new therapies underscores the importance of early molecular diagnosis and genotype-phenotype characterization. Objective. To describe 27 years of experience in the molecular diagnosis of SMA at a pediatric referral hospital in Argentina and to evaluate the correlation between SMN2 copy number and the SMA types.Population and methods. A retrospective descriptive study was conducted on 1060 pediatric patients with clinically suspected SMA who were evaluated between 1997 and 2024. Molecular diagnosis was performed using PCR-RFLP and, since 2012, MLPA to determine SMN1 and SMN2 copy number. Genotype-phenotype correlation was evaluated in 260 patients with complete clinical characterization. Results. The diagnosis was confirmed in 513 patients. A homozygous deletion of the SMN1 gene was detected in 99.6% of unrelated cases. The positivity rate increased over time. A significant correlation was observed between the number of SMN2 copies and the type of SMA, with milder phenotypes associated with a higher number of copies. Conclusion. Molecular diagnosis of SMA enabled accurate and timely characterization of patients, avoiding invasive procedures and optimizing therapeutic decision-making. Genotype-phenotype correlation is a fundamental tool for prognosis and clinical management, highlighting the importance of an interdisciplinary approach.

Argentina↗
PubMed1994

Two 5q13 simple tandem repeat loci are in linkage disequilibrium with type 1 spinal muscular atrophy.

The gene for the common recessive neuromuscular disorder spinal muscular atrophy (SMA) has been previously mapped to chromosome 5q. We report here linkage disequilibrium analyses of two polymorphic simple tandem repeat (STR) sequences which map into the critical region of 5q13 containing the SMA gene. The polymorphisms presented are constituents of CATT-1, a complex STR which is present in as many as four or more copies per chromosome 5. The PCR can amplify as many as eight CATT-1 products of different sizes from genomic DNA samples due to differing numbers of CA dinucleotides at each STR location (sublocus). Oligonucleotide primers for two of these subloci have been developed for specific PCR assays; a variety of allele sizes can be generated with each assay and, in some cases, no amplification products are detected due to null alleles. The genotyping of 149 SMA Type 1 chromosomes and 142 normal chromosomes from Canadian and American kindreds reveals the presence of significant linkage disequilibrium between the null allele of the sublocus referred to as CATT-40G1 and mutation(s) causing SMA Type 1 (Werdnig-Hoffmann disease). Allele 2 of the second sublocus, CATT-192F7, is also in linkage disequilibrium with SMA Type 1 although the degree of this association is less than that found for CATT-40G1. The proximal and distal STRs from the critical region, D5S435 and D5S351, showed no linkage disequilibrium with SMA. The data presented here will serve as a framework for future linkage disequilibrium analyses, expediting the final stage of the search for the SMA gene.

Alleles↗