Objective measurement of oral function in adults with spinal muscular atrophy

BACKGROUND

Impairment of bulbar function in adult individuals with spinal muscular atrophy (SMA) usually is not assessed by established motor scores. Measurements of oral function including quantitative muscle and endurance tests are able to detect subtle changes. The aim of this study was to systematically evaluate the measurement of maximum bite force and endurance, maximum tongue pressure and endurance, as well as maximum mouth opening in adult individuals with SMA types 2 and 3.

METHODS

Data from oral function tests in 43 individuals were analyzed. Differences in oral function between individuals with different SMA types and numbers of SMN2 copies were tested. Spearman´s rho correlations among oral function measures themselves as well as with established clinical outcome scales were analyzed.

RESULTS

The absolute maximum measures of oral function (maximum bite force, maximum tongue pressure, maximum mouth opening) were able to discriminate between individuals with different SMA types, individuals with a different number of SMN2 copies and with different walking abilities. The pairwise correlations of the absolute maximum measures of oral function were fair to moderate in size; the same was true for their correlations with the established motor scores. All correlations assessing endurance measures of oral function were weaker and statistically insignificant.

CONCLUSIONS

Among the oral function tests maximum tongue pressure and maximum mouth opening are particulary promising as clinical and sensitive outcome measures for clinical trials. Oral function tests may supplement existing motor scores, in particular concerning specific questions about bulbar function or in severely affected non-ambulatory individuals where mild (treatment-related) changes would otherwise remain undetected. Trial registration DRKS, DRKS00015842. Registered 30 July 2019, https://drks.de/search/de/trial/DRKS00015842.

Combinatorial ASO-mediated therapy with low dose SMN and the protective modifier Chp1 is not sufficient to ameliorate SMA pathology hallmarks

Spinal muscular atrophy (SMA) is a devastating genetically inherited neuromuscular disorder characterized by the progressive loss of motor neurons in the spinal cord, leading to muscle atrophy and weakness. Although SMA is caused by homozygous mutations in SMN1, the disease severity is mainly determined by the copy number of SMN2, an almost identical gene that produces ~10% correctly spliced SMN transcripts. Recently, three FDA- and EMA-approved therapies that either increase correctly spliced SMN2 transcripts (nusinersen and risdiplam) or replace SMN1 (onasemnogen abeparvovec-xioi) have revolutionized the clinical outcome in SMA patients. However, for severely affected SMA individuals carrying only two SMN2 copies even a presymptomatic therapy might be insufficient to fully counteract disease development. Therefore, SMN-independent compounds supporting SMN-dependent therapies represent a promising therapeutic approach. Recently, we have shown a significant amelioration of SMA disease hallmarks in a severely affected SMA mouse carrying a mutant Chp1 allele when combined with low-dose of SMN antisense oligonucleotide (ASO) treatment. CHP1 is a direct interacting partner of PLS3, a strong protective modifier of SMA. Both proteins ameliorate impaired endocytosis in SMA and significantly restore pathological hallmarks in mice. Here, we aimed to pharmacologically reduce CHP1 levels in an ASO-based combinatorial therapy targeting SMN and Chp1. Chp1 modulation is a major challenge since its genetic reduction to ~50% has shown to ameliorate SMA pathology, while the downregulation below that level causes cerebellar ataxia. Efficacy and tolerability studies determined that a single injection of 30 μg Chp1-ASO4 in the CNS is a safe dosage that significantly reduced CHP1 levels to ~50% at postnatal day (PND)14. Unfortunately, neither electrophysiological predictors such as compound muscle action potential (CMAP) or motor unit number estimation (MUNE) nor histological hallmarks of SMA in neuromuscular junction (NMJ), spinal cord or muscle were ameliorated in SMA mice treated with Chp1-ASO4 compared to CTRL-ASO at PND21. Surprisingly, CHP1 levels were almost at control level 4-weeks post injection, indicating a rather short-term effect of the ASO. Therefore, we re-administrated Chp1-ASO4 by i.c.v. bolus injection at PND28. However, no significant improvement of SMA hallmarks were seen at 2 month-of-age either. In conclusion, in contrast to the protective effect of genetically-induced Chp1 reduction on SMA, combinatorial therapy with Chp1- and SMN-ASOs failed to significantly ameliorate the SMA pathology. Chp1-ASOs compared to SMN-ASO proved to have rather short-term effect and even reinjection had no significant impact on SMA progression, suggesting that further optimization of the ASO may be required to fully explore the combination.

Respiratory muscle endurance training reduces chronic neck pain: A pilot study

BACKGROUND

Patients with chronic neck pain show also respiratory dysfunctions.

OBJECTIVE

To investigate the effects of respiratory muscle endurance training (RMET) on chronic neck pain.

METHODS

In this pilot study (single-subject design: 3 baseline measurements, 4 measurements during RMET), 15 neck patients (49.3 ± 13.7 years; 13 females) conducted 20 sessions of home-based RMET using a SpiroTiger® (normocapnic hyperpnoea). Maximal voluntary ventilation (MVV), maximal inspiratory (Pimax) and expiratory (Pemax) pressure were measured before and after RMET. Neck flexor endurance, cervical and thoracic mobility, forward head posture, chest wall expansion and self-assessed neck disability [Neck Disability Index (NDI), Bournemouth questionnaire] were weekly assessed. Repeated measure ANOVA (Bonferroni correction) compared the first and last baseline and the last measurement after RMET.

RESULTS

RMET significantly increased MVV (p= 0.025), Pimax (p= 0.001) and Pemax (p< 0.001). During RMET, neck disability significantly decreased (NDI: p= 0.001; Bournemouth questionnaire: p= 0.002), while neck flexor endurance (p< 0.001) and chest wall expansion (p< 0.001) increased. The changes in respiratory and musculoskeletal parameters did not correlate.

CONCLUSIONS

RMET emerged from this pilot study as a feasible and effective therapy for reducing disability in patients with chronic neck pain. The underlying mechanisms, including blood gas analyses, need further investigation in a randomized controlled study.

[Prostate biopsy: Procedure in the clinical routine]

Over the last decade there has been a 25% decrease in the mortality rates for prostate cancer. The reasons for this significant decrease are most likely associated with the application of urological screening tests. The main tools for early detection are currently increased public awareness of the disease, prostate-specific antigen (PSA) tests and transrectal ultrasound (TRUS) guided topographically assignable biopsy sampling. Together with the histopathological results these features provide essential information for risk stratification, diagnostics and therapy decisions. The evolution of prostate biopsy techniques as well as the use of PSA testing has led to an increased identification of asymptomatic men, where further clarification is necessary. Significant efforts and increased clinical research focus on determining the appropriate indications for a prostate biopsy and the optimal technique to achieve better detection rates. The most widely used imaging modality for the prostate is TRUS; however, there are no clearly defined standards for the clinical approach for each individual biopsy procedure, dealing with continuous technical optimization and in particular the developments in imaging. In this review the current principles, techniques, new approaches and instrumentation of prostate biopsy imaging control are presented within the framework of the structured educational approach.

Respiratory dysfunction in patients with chronic neck pain - influence of thoracic spine and chest mobility

Patients with chronic neck pain exhibit various musculoskeletal deficits and respiratory dysfunction. As there is a link between thoracic and cervical spine motion, the aim of this study was to investigate the relationship between thoracic spine and chest mobility with respiratory function and neck disability. Nineteen patients with chronic neck pain (7 male, 46.6 ± 10.5 years) and 19 healthy subjects (7 male, 46.5 ± 9.9 years) participated. Spirometry was conducted to determine maximal voluntary ventilation (MVV), maximal inspiratory (Pimax) and maximal expiratory pressure (Pemax). Thoracic spine mobility was measured using the Spinal Mouse(®). Chest expansion was assessed by subtracting chest circumference during maximal inspiration and expiration. Neck function was investigated by examining range of motion, forward head posture, neck flexor muscle synergy endurance and self-assessment (Neck disability index (NDI)). Correlation analyses and multiple linear regression analyses were conducted using MVV, Pimax and Pemax as independent variables. Thoracic spine mobility during flexion and chest expansion correlated significantly to MVV (r = 0.45 and 0.42), all neck motions (r between 0.39 and 0.59) and neck muscle endurance (rS = 0.36). Pemax and Pimax were related to NDI (r = -0.58 and -0.46). In the regression models, chest expansion was the only significant predictor for MVV, and Pemax was determined by neck muscle endurance. These results suggest that chronic neck pain patients should improve the endurance of the neck flexor muscles and thoracic spine and chest mobility. Additionally, these patients might benefit from respiratory muscle endurance training, possibly by increasing chest mobility and Pemax.

[Development and evaluation of a German version of the Tegner activity scale for measuring outcome after anterior cruciate ligament injury]

BACKGROUND

The aim of this study is to provide a valid and reliable German version of the Tegner activity scale (Tegner-G). The Tegner activity scale assesses on 11 levels the activity in sports (competitive and recreational) and work of patients with anterior cruciate ligament injuries. The English original version was elaborated in Sweden and contains sports that are unknown in German-speaking countries.

METHODS

The translation and adaptation was conducted in several steps according to the guidelines in the literature. The validity (discriminative validity and content validity) and (absolute and relative) reliability were determined in 46 patients after reconstruction of the anterior cruciate ligament and in 20 healthy subjects. The patients were divided into an acute group (< 3 months after operation; 11 men; 30.9 ± 8.3 years) and a chronic group (3 - 12 months after operation; 18 men; 31.3 ± 11.6 years). All subjects filled in the scale two times within 3 - 7 days. For the additional determination of the relation between activity and function, they also filled in the German version of the Lysholm score (Lysholm-G).

RESULTS

The three groups differed significantly from each other (Kruskal-Wallis test: χ2 = 27.95, p < 0.001; post hoc Mann-Whitney U tests: acute-chronic p < 0.001; acute-control p < 0.001; chronic-control p = 0.003). There was a floor effect in the acute patient group. The intraclass correlation coefficients indicated a high relative reliability (ICC2,1 > 0.9). The minimal detectable change was 1.4 points. The relation between activity (Tegner-G) and function (Lysholm-G) was stronger in the acute than in the chronic patient group (ρ = 0.77 and ρ = 0.60, respectively).

CONCLUSION

The psychometric properties of the Tegner-G are comparable to those of the English original version. The Tegner-G is thus valid and reliable for the German-speaking part of Switzerland. The application in other German-speaking countries probably requires adaptations for some of the sports included. The relation between activity and function changes depending on time since operation. This confirms that a comprehensive assessment of the outcome after an anterior cruciate ligament injury requires the separate assessment of both parameters.

Whole body vibration added to endurance training in obese women - a pilot study

Whole body vibration (WBV) training is an increasingly popular training method that is strongly promoted for weight loss, but scientific data on its effectiveness, particularly in obese subjects, are sparse. 14 obese women (BMI: 37.4 ± 1.3 kg/m2) randomized to 2 different groups (each n=7) participated in a 6-week endurance training program that was either combined or not combined with additional WBV training. Anthropometric measures, phase angle and body composition (assessed by bioelectrical impedance analysis; BIA), and resting energy expenditure (REE) were obtained before and after the training program. Body weight did not change during the training period (P=0.87), but waist circumference decreased in both groups (P=0.007; WBV: -3.4 ± 1.4 cm; no-WBV: -1.7 ± 0.7 cm) independent of WBV training (P=0.29 for group×time interaction). BIA revealed an enhancing effect of WBV training in comparison to no-WBV training on the phase angle (+0.20 ± 0.12° vs. -0.19 ± 0.12°; P=0.04) and calculated body cell mass (+0.8 ± 0.2 vs. -0.3 ± 0.4 kg; P=0.02), while calculated percentage fat mass decreased in both conditions (P=0.05) to similar extent (P=0.59; WBV: -0.8 ± 0.2%; no-WBV: -0.4 ± 0.5%). REE increased across the training (P=0.01; WBV: +77 ± 33 kcal/24 h; no-WBV: +68 ± 34 kcal/24 h), with this increase again not depending on WBV condition (P=0.85). Results of our pilot study in obese women provide preliminary evidence for a beneficial effect of WBV, when added to endurance training, on the bioelectrical phase angle, an increasingly recognized marker of individual's health status.

Is a positive clinical outcome after exercise therapy for chronic non-specific low back pain contingent upon a corresponding improvement in the targeted aspect(s) of performance? A systematic review

INTRODUCTION

The effect size for exercise therapy in the treatment of chronic non-specific low back pain (cLBP) is only modest. This review aims to analyse the specificity of the effect by examining the relationship between the changes in clinical outcome (pain, disability) and the changes in the targeted aspects of physical function (muscle strength, mobility, muscular endurance) after exercise therapy.

METHODS

We searched for exercise therapy trials for cLBP published up to 15 April 2010 in Medline, Embase, Cochrane Library, Cinahl, and PEDro. Two independent reviewers selected studies according to the inclusion criteria.

DATA EXTRACTION

one author extracted the data of the articles.

RESULTS

DATA SYNTHESIS

16 studies with a total of 1,476 participants met the inclusion criteria. There was little evidence supporting a relationship between the changes in pain or physical function and the changes in performance for the following measures: mobility (no correlation in 9 studies, weak correlation in 1 study), trunk extension strength (7 and 2, respectively), trunk flexion strength (4 and 1, respectively) and back muscle endurance (7 and 0, respectively). Changes in disability showed no correlation with changes in mobility in three studies and a weak correlation in two; for strength, the numbers were four (no correlation) and two (weak correlation), respectively.

CONCLUSIONS

The findings do not support the notion that the treatment effects of exercise therapy in cLBP are directly attributable to changes in the musculoskeletal system. Future research aimed at increasing the effectiveness of exercise therapy in cLBP should explore the coincidental factors influencing symptom improvement.

[Development and evaluation of a German version of the Lysholm score for measuring outcome after anterior cruciate ligament injuries]

BACKGROUND

The Lysholm score is a questionnaire that assesses knee function after conservatively or operatively treated anterior cruciate ligament (ACL) injuries. Its original version is in English and consists of eight items (limping, support, locking, instability, pain, swelling, stair-climbing, squatting). The aim of this study was to translate the Lysholm score in the German language, to test discriminative validity and reliability of this German version and, thus, to provide a validated German version of the Lysholm score to be applied in further studies.

METHODS

The cross-cultural adaptation to the German language was performed according to recommended guidelines in the literature. Validity and reliability of the German version were tested in two patient groups in the acute (< 3 months post incident/operation; n = 12) and late rehabilitation phase after ACL injury (3 - 12 months post incident/operation, n = 16), respectively as well as in a control group without any knee problems (n = 22). The subjects filled in the questionnaire twice within three days.

RESULTS

With respect to validity, the control group (total score 96.8 ± 5.1 points) differed significantly from the total patient group (p < 0.001) as well as from the patient group in the acute (75.3 ± 16.8 points) (p < 0.001) and the late (82.7 ± 12.8 Punkte) (p < 0.001) rehabilitation phase, respectively. Test-retest reliability of the total Lysholm score was good for the total patient group (intraclass correlation coefficient (ICC) = 0.82) as well as for the patients in the acute (ICC = 0.82) and in the late (ICC = 0.84) rehabilitation phase, respectively. The Cronbachs Alpha was 0.73.

CONCLUSION

The psychometric properties of the German version of the Lysholm score are comparable to the English version. It is a valid and reliable instrument for the objective assessment of rehabilitation outcome after ACL injury at least in the German speaking part of Switzerland. Based on these first results, its application for further research projects in all German speaking countries is recommended.

Congenital heart disease is a feature of severe infantile spinal muscular atrophy

OBJECTIVE

Homozygous deletions/mutations of the SMN1 gene cause infantile spinal muscular atrophy (SMA). The presence of at least one SMN2 gene copy is required for normal embryogenesis. Lack of SMN protein results in degeneration of motor neurons, while extraneuronal manifestations have been regarded as a chance association with SMA. We report on heart defects in the subgroup of congenital SMA type I patients.

METHODS

Data were recruited from 65 unselected SMA I patients whose diagnosis had been confirmed genetically within the first 6 months of age. SMN2 copy numbers were analysed retrospectively and correlated with clinical findings including heart malformations.

RESULTS

Four (6%) patients had one copy of SMN2, 56 (86%) had two and five (8%) had three SMN2 copies. Three out of four (75%) patients with a single SMN2 copy had congenital SMA with haemodynamically relevant atrial or ventricular septal defects.

CONCLUSIONS

Previous case reports of SMA I patients with congenital heart defects did not clarify whether the cardiac malformations were coincidental. Given the respective incidences of congenitally lethal SMA with a single SMN2 copy and of cardiac septal defects in humans, a chance association of both conditions would occur in less than one out of 50 million individuals. Our findings suggest that the SMN protein is relevant for normal cardiogenesis.

Mildly affected patients with spinal muscular atrophy are partially protected by an increased SMN2 copy number

Spinal muscular atrophy (SMA) is a recessive neuromuscular disorder caused by loss of the SMN1 gene. The clinical distinction between SMA type I to IV reflects different age of onset and disease severity. SMN2, a nearly identical copy gene of SMN1, produces only 10% of full-length SMN RNA/protein and is an excellent target for a potential therapy. Several clinical trials with drugs that increase the SMN2 expression such as valproic acid and phenylbutyrate are in progress. Solid natural history data for SMA are crucial to enable a correlation between genotype and phenotype as well as the outcome of therapy. We provide genotypic and phenotypic data from 115 SMA patients with type IIIa (age of onset <3 years), type IIIb (age of onset >3 years) and rare type IV (onset >30 years). While 62% of type IIIa patients carry two or three SMN2 copies, 65% of type IIIb patients carry four or five SMN2 copies. Three type IV SMA patients had four and one had six SMN2 copies. Our data support the disease-modifying role of SMN2 leading to later onset and a better prognosis. A statistically significant correlation for > or =4 SMN2 copies with SMA type IIIb or a milder phenotype suggests that SMN2 copy number can be used as a clinical prognostic indicator in SMA patients. The additional case of a foetus with homozygous SMN1 deletion and postnatal measurement of five SMN2 copies illustrates the role of genotypic information in making informed decisions on the management and therapy of such patients.

Molecular and functional analysis of intragenic SMN1 mutations in patients with spinal muscular atrophy

The autosomal recessive spinal muscular atrophy (SMA), a neuromuscular disease and frequent cause of early death in childhood, is caused in 96% of patients by homozygous absence of the survival motor neuron gene (SMN1). The severity of the disease is mainly determined by the copy number of SMN2, a copy gene which predominantly produces exon 7-skipped transcripts and only low amount of full-length transcripts that encode for a protein identical to SMN1. Only about 4% of SMA patients bear one SMN1 copy with an intragenic mutation. A comprehensive molecular genetic analysis of 34 SMA patients who carry one SMN1 gene is presented, including 18 that were previously published. Haplotype analysis with the microsatellite markers Ag1-CA and C212 in these SMA families turned out to be a reliable accessory method in predicting known SMN1 mutations in SMA patients carrying one SMN1 copy. Five novel missense mutations were identified that are localized in: exon 2a c.88G>A (p.D30N) and c.131A>T (p.D44V); exon 3 c.283G>C (p.G95R) and c.332C>G (p.A111G); and exon 6 c.784A>G (p.S262G), respectively. The survival motor neuron (SMN) protein has been shown to be a component of a large complex (termed the SMN complex) that promotes the formation of spliceosomal U small nuclear ribonucleoproteins (snRNPs). Within this complex, SMN forms oligomers and directly interacts via its N-terminus with SMN-interacting protein 1 (SIP1) and via its central Tudor domain with spliceosomal (Sm) proteins. We performed in vitro interaction studies to test whether SMA-causing missense mutations identified in this study interfere with the reported interactions of SMN. Our results show that mutations p.G95R and p.A111G reduce SMN binding to Sm proteins, further confirming the previous finding that the Tudor domain is the essential binding site of SMN to Sm-proteins. However, all mutations, including those in exon 2a, a region shown to be important for the binding of SMN to SIP1, do not disturb the interaction of SMN to SIP1.

Limits of locomotor ability in subjects with a spinal cord injury

STUDY DESIGN

Case-control study with pair-wise matching.

OBJECTIVES

To investigate the level of locomotor performance in spinal cord injury (SCI) subjects.

SETTING

Spinal Cord Injury Center of Balgrist University Hospital in Zurich, Switzerland.

METHODS

Seven well-recovered SCI subjects and controls performed three tests: (1) 6-Min Walk Test (6MWT), (2) treadmill walking with full and restricted vision and (3) repetitive stepping over an obstacle. In the latter task, the subjects had to step over an obstacle as low as possible, without touching it. The subjects performed three blocks of 50 trials each. They received acoustic signals that indicated obstacle approach and foot clearance. During the third block, vision was restricted. The main outcome measures were: (1) distance walked, (2) leg muscle activity, joint kinematics and double-support duration, (3) foot clearance, number of obstacle hits, leg muscle activity, joint kinematics and swing phase duration.

RESULTS

(1) No difference in the 6MWT between the groups. (2) Independent from vision, the double-support duration was increased in SCI subjects. (3) SCI subjects learned generally at a slower rate. They touched the obstacle more frequently when vision became restricted. Furthermore, we observed differences between the groups in rectus femoris and tibialis anterior EMG activity and swing phase duration.

CONCLUSION

It appears that even in well-recovered SCI subjects, small deficiencies in functional gait can be determined, which remain undetected by clinical walking tests. In addition, SCI subjects learned a locomotor task at a slower rate. This indicates that rehabilitation programs should train (adaptive) locomotion in different (sensory) environments.

Differential evolution of the Saccharomyces cerevisiae DUP240 paralogs and implication of recombination in phylogeny

Multigene families are observed in all genomes sequenced so far and are the reflection of key evolutionary mechanisms. The DUP240 family, identified in Saccharomyces cerevisiae strain S288C, is composed of 10 paralogs: seven are organized as two tandem repeats and three are solo ORFs. To investigate the evolution of the three solo paralogs, YAR023c, YCR007c and YHL044w, we performed a comparative analysis between 15 S.cerevisiae strains. These three ORFs are present in all strains and the conservation of synteny indicates that they are not frequently involved in chromosomal reshaping, in contrast to the DUP240 ORFs organized in tandem repeats. Our analysis of nucleotide and amino acid variations indicates that YAR023c and YHL044w fix mutations more easily than YCR007c, although they all belong to the same multigene family. This comparative analysis was also conducted with five arbitrarily chosen Ascomycetes-specific genes and five arbitrarily chosen common genes (genes that have a homolog in at least one non-Ascomycetes organism). Ascomycetes-specific genes appear to be diverging faster than common genes in the S.cerevisiae species, a situation that was previously described between different yeast species. Our results point to the strong contribution, during DNA sequence evolution, of allelic recombination besides nucleotide substitution.

Valproic acid increases the SMN2 protein level: a well-known drug as a potential therapy for spinal muscular atrophy

Proximal spinal muscular atrophy (SMA) is a common neuromuscular disorder causing infant death in half of all patients. Homozygous absence of the survival motor neuron gene (SMN1) is the primary cause of SMA, while SMA severity is mainly determined by the number of SMN2 copies. One SMN2 copy produces only about 10% of full-length protein identical to SMN1, whereas the majority of SMN2 transcripts is aberrantly spliced due to a silent mutation within an exonic splicing enhancer in exon 7. However, correct splicing can be restored by over-expression of the SR-like splicing factor Htra2-beta 1. We show that in fibroblast cultures derived from SMA patients treated with therapeutic doses (0.5-500 microM) of valproic acid (VPA), the level of full-length SMN2 mRNA/protein increased 2- to 4-fold. Importantly, this up-regulation of SMN could be most likely attributed to increased levels of Htra2-beta 1 which facilitates the correct splicing of SMN2 RNA as well as to an SMN gene transcription activation. Especially at low VPA concentrations, the restored SMN level depended on the number of SMN2 copies. Moreover, VPA was able to increase SMN protein levels through transcription activation in organotypic hippocampal brain slices from rats. Finally, VPA also increased the expression of further SR proteins, which may have important implications for other disorders affected by alternative splicing. Since VPA is a drug highly successfully used in long-term epilepsy therapy, our findings open the exciting perspective for a first causal therapy of an inherited disease by elevating the SMN2 transcription level and restoring its correct splicing.

Classical infantile spinal muscular atrophy with SMN deficiency causes sensory neuronopathy

OBJECTIVE

Classic infantile spinal muscular atrophy (SMA) is believed to be a purely motor disorder, affecting neurons of the spinal anterior horn and nuclei of the lower cranial nerves. Other organ malformations or peripheral nerve involvement have been regarded as exclusion criteria for infantile SMA. Whether SMN protein deficiency can also lead to loss of sensory neurons has not been systematically addressed.

METHODS

The authors evaluated the sural nerve biopsies of 19 patients with infantile SMA of varying severity. The diagnosis of SMA was confirmed by the presence of a homozygous deletion of the SMN1 gene in all patients.

RESULTS

In seven unrelated infants with SMA type I, axonal degeneration of the sural nerve was noted. Five patients showed abnormal sensory conduction, thus prompting sural nerve biopsy. Sural nerves showed different degrees of axonal loss: fiber density ranged from 3.482 to 22.076/mm2 and was markedly reduced in four patients. There was no evidence of primary demyelination: the ratio of total myelinated fiber thickness to axon diameter (g-ratio) was normal in the patients examined. In seven patients with SMA II and five patients with SMA III, no sural nerve alterations were seen, and conduction velocity was normal. In addition to SMN1 gene deletions, homozygous NAIP gene deletions were detected in six out of seven infants with peripheral neuropathy, whereas there was no evidence of a large deletion including the multicopy markers C212 and Ag1-CA in two out of three families tested.

CONCLUSIONS

In this series of patients with SMA I through III who underwent sural nerve biopsy, there was significant sensory nerve pathology in severely affected patients with SMA type I, whereas there were no sensory nerve alterations clinically or morphologically in patients with milder SMA type II or III.

Best practice guidelines for molecular analysis in spinal muscular atrophy

With a prevalence of approximately 1/10 000, and a carrier frequency of 1/40-1/60 the proximal spinal muscular atrophies (SMAs) are among the most frequent autosomal recessive hereditary disorders. Patients can be classified clinically into four groups: acute, intermediate, mild, and adult (SMA types I, II, III, and IV, respectively). The complexity and instability of the genomic region at chromosome 5q13 harbouring the disease-causing survival motor neuron 1 (SMN1) gene hamper molecular diagnosis in SMA. In addition, affected individuals with SMA-like phenotypes not caused by SMN1, and asymptomatic individuals with two mutant alleles exist. The SMN gene is present in at least one telomeric (SMN1) and one centromeric copy (SMN2) per chromosome in normal (non-carrier) individuals, although chromosomes containing more copies of SMN1 and/or SMN2 exist. Moreover, the two SMN genes (SMN1 and SMN2) are highly homologous and contain only five base-pair differences within their 3' ends. Also, a relatively high de novo frequency is present in SMA. Guidelines for molecular analysis in diagnostic applications, carrier detection, and prenatal analysis using direct and indirect approaches are described. Overviews of materials used in the molecular diagnosis as well as Internet resources are included.

The critical incident stress debriefing process for the Los Angeles County Fire Department: automatic and effective

Los Angeles County Fire Department has one of the oldest Critical Incident Stress Management (CISM) programs in the country. One core component for the LACoFD has been the Critical Incident Stress Debriefing (CISD). Two important questions for the emergency managers are: 1) Do individuals find a significant difference in symptom reduction for events that were debriefed? 2) Does helpfulness of a debriefing for a specific individual correlate with recommending the process for others? A Department-wide evaluative survey was conducted in 1996 to determine the satisfaction and effectiveness of the debriefing program. Individuals reported a significant difference in the speed of symptom reduction for incidents that were debriefed versus incidents that were not debriefed. The majority of individuals would recommend the debriefing process to others regardless of whether they personally found the process helpful or not. Based on this, the recommendations are to continue the debriefing process for specific events and to make the process mandatory; furthermore, it is recommended that the term "mandatory" be changed to "automatic." By using the term "automatic," debriefings become standard operating procedures. By doing so, a method to protect the psychological welfare of emergency personnel becomes as automatic as putting on safety protection equipment [International Journal of Emergency Mental Health, 2000, 2(4), 249-257].

Co-regulation of survival of motor neuron (SMN) protein and its interactor SIP1 during development and in spinal muscular atrophy

Spinal muscular atrophy (SMA) is a neuromuscular disease characterized by the degeneration of motor neurons in the spinal cord. The disease is caused by mutations of the survival of motor neuron 1 gene (SMN1), resulting in a reduced production of functional SMN protein. A major question unanswered thus far is why reduced amounts of ubiquitously expressed SMN protein specifically cause the degeneration of motor neurons without affecting other somatic cell types. In a first attempt to address this issue we have investigated the Smn interacting protein 1 (Sip1), with an emphasis on its developmental expression and subcellular distribution in spinal motor neurons in relation to Smn. By confocal immunofluorescence studies we provide evidence that a significant amount of Smn does not co-localize with Sip1 in neurites of motor neurons, indicating that Smn may exert motor neuron-specific functions that are not dependent on Sip1. Sip1 is highly expressed in the spinal cord during early development and expression decreases in parallel with Smn during postnatal development. Strikingly, reduced production of Smn as observed in cell lines derived from SMA patients or in a mouse model for SMA coincides with a simultaneous reduction of Sip1. The finding that expression of Sip1 and Smn is tightly co-regulated, together with the unique localization of Smn in neurites, may help in understanding the motor neuron-specific defects observed in SMA patients.

The transcription factor-like nuclear regulator (TFNR) contains a novel 55-amino-acid motif repeated nine times and maps closely to SMN1

The transcription factor-like nuclear regulator (TFNR) is a novel human gene that maps on 5q13, distal to the duplicated region that includes SMN1, the spinal muscular atrophy (SMA) determining gene. The location of TFNR allowed us to design an evolutionary model of the SMA region. The 9.5-kb TFNR transcript is highly expressed in cerebellum and weakly in all other tissues tested. TFNR encodes a protein of 2254 amino acids (aa) and contains nine repeats of a novel 55-aa motif, of yet unknown function. The coding region is organized in 32 exons. Alternative splicing of exon 15 results in a truncated protein of 796 aa. TFNR comprises a series of polypeptides that range from 55 to 250 kDa. Immunocytological studies showed that the TFNR protein is present exclusively in the nucleus, where it is concentrated in several nuclear structures. Amino acids 155-474 show significant homology to TFC5, a subunit of the yeast transcription factor TFIIIB, suggesting that TFNR is a putative transcription factor. Based on its proximity to SMN1 and its expression pattern, TFNR may be a candidate gene for atypical forms of SMA with cerebral atrophy and axonal neuropathy that have been shown to carry large deletions in the SMA region.

Exclusion of Htra2-beta1, an up-regulator of full-length SMN2 transcript, as a modifying gene for spinal muscular atrophy

Spinal muscular atrophy (SMA) is a neurodegenerative disease caused by homozygous mutations of the survival motor neuron gene 1 (SMN1). In rare cases sibs with identical 5q13-homologs and identical SMN1 mutations can show variable phenotypes from unaffected to affected, suggesting the influence of modifying genes. SMN is part of an 800 kDa macromolecular complex that plays an essential role in snRNP biogenesis and pre-mRNA splicing. Due to a single nucleotide difference within SMN1 exon 7 that disrupts an exonic splicing enhancer (ESE), SMN2, a nearly identical copy of SMN1, predominantly expresses alternatively spliced transcripts lacking exon 7, whereas SMN1 mainly produces full-length transcripts. The SR-like trans-acting splicing factor Htra2-beta1 was shown to interact with this ESE and to restore full-length SMN2 expression in vivo in a concentration-dependent manner. Since Htra2-beta1 prevents skipping of exon 7 it is obvious to ask whether mutations within Htra2-beta1 are responsible for the intrafamilial variability of the SMA phenotype. We sequenced either RT-PCR products or genomic DNA covering the complete coding region of Htra2-beta1 as well as the putative promoter of 36 sibs belonging to 15 SMA families with discordant phenotypes but identical genotypes. Neither a mutation nor a polymorphism was found within Htra2-beta1. Additionally, we performed quantitative analysis of Htra2-beta isoforms from 26 sibs without identifying any significant difference between phenotypically discordant sibs. Based on these data, we suggest that the intrafamilial phenotypic variability in SMA families is not caused by polymorphic variants or transcription differences within Htra2-beta1.

Htra2-beta 1 stimulates an exonic splicing enhancer and can restore full-length SMN expression to survival motor neuron 2 (SMN2)

Spinal muscular atrophy (SMA), a common motor neuron disease in humans, results from loss of functional survival motor neuron (SMN1) alleles. A nearly identical copy of the gene, SMN2, fails to provide protection from SMA because of a single translationally silent nucleotide difference in exon 7. This likely disrupts an exonic splicing enhancer and causes exon 7 skipping, leading to abundant production of a shorter isoform, SMN2Delta7. The truncated transcript encodes a less stable protein with reduced self-oligomerization activity that fails to compensate for the loss of SMN1. This report describes the identification of an in vivo regulator of SMN mRNA processing. Htra2-beta1, an SR-like splicing factor and ortholog of Drosophila melanogaster transformer-2, promoted the inclusion of SMN exon 7, which would stimulate full-length SMN2 expression. Htra2-beta1 specifically functioned through and bound an AG-rich exonic splicing enhancer in SMN exon 7. This effect is not species-specific as expression of Htra2-beta1 in human or mouse cells carrying an SMN2 minigene dramatically increased production of full-length SMN2. This demonstrates that SMN2 mRNA processing can be modulated in vivo. Because all SMA patients retain at least one SMN2 copy, these results show that an in vivo modulation of SMN RNA processing could serve as a therapeutic strategy to prevent SMA.

An essential SMN interacting protein (SIP1) is not involved in the phenotypic variability of spinal muscular atrophy (SMA)

The survival motor neuron (SMN) protein and the SMN interacting protein 1 (SIP1) are part of a 300 kD protein complex with a crucial role in snRNP biogenesis and pre-mRNA splicing. Both proteins are colocalised in nuclear structures called gems and in the cytoplasm. Approximately 96% of patients with autosomal recessive spinal muscular atrophy (SMA) show mutations in the SMN1 gene, while about 4% fail to show any mutation, despite a typical SMA phenotype. Additionally, sibs with identical 5q13 homologs and homozygous absence of SMN1 can show variable phenotypes which suggest that SMA is modified by other, yet unknown factors. Since both genes, SMN1 and SIP1, belong to the same pathway and are part of the same protein complex, it is obvious to ask whether mutations within SIP1 are responsible for both the phenotypic variability and the appearance of non-SMN mutated SMA patients. First, we identified the chromosomal location of SIP1 and assigned it to chromosomal region 14q13-q21 by fluorescence in situ hybridisation. No SMA related disorder has yet been assigned to this chromosomal region. Next, we determined the exon-intron structure of the SIP1 gene which encompasses 10 exons and identified five transcription isoforms. We sequenced either RT-PCR products or genomic DNA covering the complete coding region from 23 typical SMA patients who had failed to show any SMN1 mutation. No mutation and no polymorphism was found within SIP1. Additionally, we sequenced RT-PCR products or genomic fragments of the entire SIP1 coding region from 26 sibs of 11 SMA families with identical genotypes (delta7SMN/delta7SMN or delta7SMN/other mutation) but different phenotypes and again no mutation was found. Finally, we performed quantitative analysis of RT-PCR products from the same 26 sibs. No difference in expression level of the five isoforms among phenotypically variable sibs was observed. Based on these data, we suggest that neither the phenotypic variability nor the 5q-unlinked SMA are caused by mutations within SIP1.

An update of the mutation spectrum of the survival motor neuron gene (SMN1) in autosomal recessive spinal muscular atrophy (SMA)

Spinal muscular atrophy (SMA) is characterized by degeneration of motor neurons in the spinal cord, causing progressive weakness of the limbs and trunk, followed by muscle atrophy. SMA is one of the most frequent autosomal recessive diseases, with a carrier frequency of 1 in 50 and the most common genetic cause of childhood mortality. The phenotype is extremely variable, and patients have been classified in type I-III SMA based on age at onset and clinical course. All three types of SMA are caused by mutations in the survival motor neuron gene (SMN1). There are two almost identical copies, SMN1 and SMN2, present on chromosome 5q13. Only homozygous absence of SMN1 is responsible for SMA, while homozygous absence of SMN2, found in about 5% of controls, has no clinical phenotype. Ninety-six percent of SMA patients display mutations in SMN1, while 4% are unlinked to 5q13. Of the 5q13-linked SMA patients, 96.4% show homozygous absence of SMN1 exons 7 and 8 or exon 7 only, whereas 3. 6% present a compound heterozygosity with a subtle mutation on one chromosome and a deletion/gene conversion on the other chromosome. Among the 23 different subtle mutations described so far, the Y272C missense mutation is the most frequent one, at 20%. Given this uniform mutation spectrum, direct molecular genetic testing is an easy and rapid analysis for most of the SMA patients. Direct testing of heterozygotes, while not trivial, is compromised by the presence of two SMN1 copies per chromosome in about 4% of individuals. The number of SMN2 copies modulates the SMA phenotype. Nevertheless, it should not be used for prediction of severity of the SMA.

Analysis of the SMN and NAIP genes in slovak spinal muscular atrophy patients

We identified homozygous absence of exon 7 of the telomeric copy of the survival motor neuron gene (telSMN) in 88.4% (38/43) of spinal muscular atrophy (SMA) patients from Slovakia. Additional deletions within the neuronal apoptosis inhibitory protein (NAIP) gene were found in 38.5% of type I, 12.5% of type II and never in type III SMA patients. Neither the SMN nor the NAIP gene was deleted in 81 healthy relatives and 25 controls tested. In one family, pseudodominant inheritance was identified. Both the type III SMA father and type II SMA son carried the homozygous deletion of the telSMN gene. One SMA I patient showed an SMN hybrid gene, probably created by intrachromosomal deletion. In two haploidentical type II SMA sibs, the telSMN exon 7 was absent on one chromosome, while the other carried an A-->G transition 96 bp upstream of exon 7 of the telSMN gene, a potential disease-causing mutation in these patients.