Salbutamol increases survival motor neuron (SMN) transcript levels in leucocytes of spinal muscular atrophy (SMA) patients: relevance for clinical trial design.

BACKGROUND: Spinal muscular atrophy (SMA) is a neuromuscular disorder caused by mutations of the SMN1 gene. Based on severity, three forms of SMA are recognised (types I-III). All patients usually have 2-4 copies of a highly homologous gene (SMN2) which produces insufficient levels of functional survival motor neuron (SMN) protein. Recently, evidence has been provided that SMN2 expression can be enhanced in vitro by salbutamol, a ß2-adrenergic agonist. This compound has also been shown to improve motor function of SMA patients in two different pilot trials. AIM: To evaluate the in vivo molecular efficacy of salbutamol in SMA patients. METHODS: Twelve type II-III patients took salbutamol orally for 6 months. SMN2 full length transcript levels were determined in peripheral blood leucocytes by absolute real-time PCR, at baseline and after 3 and 6 months of treatment. RESULTS: A significant and constant increase in SMN2 full length transcript levels was detected; the response was directly proportional to SMN2 gene copy number. CONCLUSIONS: The data strongly support salbutamol as a candidate for treating SMA, and suggest that SMN2 copy number may predict the molecular response to treatment and may be a useful randomisation parameter in a double blind placebo controlled clinical trial design.

Biomarkers in rare disorders: the experience with spinal muscular atrophy.

Spinal muscular atrophy (SMA) is an autosomal recessive neuromuscular disorder caused by homozygous mutations of the SMN1 gene. Based on clinical severity, three forms of SMA are recognized (type I-III). All patients have at least one (usually 2-4) copies of a highly homologous gene (SMN2) which produces insufficient levels of functional SMN protein, due to alternative splicing of exon7. Recently, evidence has been provided that SMN2 expression can be enhanced by different strategies. The availability of potential candidates to treat SMA has raised a number of issues, including the availability of data on the natural history of the disease, the reliability and sensitivity of outcome measures, the duration of the studies, and the number and clinical homogeneity of participating patients. Equally critical is the availability of reliable biomarkers. So far, different tools have been proposed as biomarkers in SMA, classifiable into two groups: instrumental (the Compound Motor Action Potential, the Motor Unit Number Estimation, and the Dual-energy X-ray absorptiometry) and molecular (SMN gene products dosage, either transcripts or protein). However, none of the biomarkers available so far can be considered the gold standard. Preclinical studies on SMA animal models and double-blind, placebo-controlled studies are crucial to evaluate the appropriateness of biomarkers, on the basis of correlations with clinical outcome.

Respiratory failure in infants due to spinal muscular atrophy with respiratory distress type 1.

BACKGROUND: Spinal muscular atrophy with respiratory distress type 1 (SMARD1) is a rare autosomal recessive neuromuscular disease of unknown prevalence characterized by degeneration of anterior horn alpha-motoneurons and manifesting in the first 6months of life as life-threatening irreversible diaphragmatic paralysis associated with progressive symmetrical muscular weakness (distal lower limbs mainly involved), muscle atrophy, and peripheral sensory neuropathy. SETTING: Pediatric intensive care unit of tertiary care hospital. PATIENTS: We present two new cases of SMARD1 and report two new mutations in the gene IGHMBP2 which encodes immunoglobulin mu-binding protein 2 on chromosome 11q13. CONCLUSIONS: SMARD1 is a poor-prognosis disease that should be considered when acute respiratory insufficiency, of suspected neuromuscular or unclear cause, develops during the first 6months of life. Diaphragmatic paralysis, manifesting as dyspnea and paradoxical respiration, is the most prominent presenting sign and diaphragmatic motility should be investigated early by fluoroscopy or ultrasound. Electromyography and nerve conduction studies revealing peripheral motor and sensory neuropathy then suggest the diagnosis which should be confirmed by genetic analysis.

Partial protective effect of CCR5-Delta 32 heterozygosity in a cohort of heterosexual Italian HIV-1 exposed uninfected individuals.

Despite multiple sexual exposure to HIV-1 virus, some individuals remain HIV-1 seronegative (exposed seronegative, ESN). The mechanisms underlying this resistance remain still unclear, although a multifactorial pathogenesis can be hypothesised. Although several genetic factors have been related to HIV-1 resistance, the homozigosity for a mutation in CCR5 gene (the 32 bp deletion, i.e. CCR5-Delta32 allele) is presently considered the most relevant one. In the present study we analysed the genotype at CCR5 locus of 30 Italian ESN individuals (case group) who referred multiple unprotected heterosexual intercourse with HIV-1 seropositive partner(s), for at least two years. One hundred and twenty HIV-1 infected patients and 120 individuals representative of the general population were included as control groups. Twenty percent of ESN individuals had heterozygous CCR5-Delta 32 genotype, compared to 7.5% of HIV-1 seropositive and 10% of individuals from the general population, respectively. None of the analysed individuals had CCR5-Delta 32 homozygous genotype. Sequence analysis of the entire open reading frame of CCR5 was performed in all ESN subjects and no polymorphisms or mutations were identified. Moreover, we determined the distribution of C77G variant in CD45 gene, which has been previously related to HIV-1 infection susceptibility. The frequency of the C77G variant showed no significant difference between ESN subjects and the two control groups. In conclusion, our data show a significantly higher frequency of CCR5-Delta 32 heterozygous genotype (p = 0.04) among the Italian heterosexual ESN individuals compared to HIV-1 seropositive patients, suggesting a partial protective role of CCR5-Delta 32 heterozygosity in this cohort.

Phenylbutyrate increases SMN gene expression in spinal muscular atrophy patients.

Spinal muscular atrophy (SMA) is caused by insufficient levels of survival motor neuron (SMN) protein. Recently, we found that sodium 4-phenylbutyrate (PB), a well-tolerated FDA approved drug, enhances SMN gene expression in vitro. We provide here the first evidence that oral administration of PB (triButyrate significantly increases SMN expression in leukocytes of SMA patients. This finding provides a strong rationale to further investigate the effects of PB as also supported by preliminary clinical data.

Phenylbutyrate increases SMN expression in vitro: relevance for treatment of spinal muscular atrophy.

Spinal muscular atrophy (SMA) is an autosomal recessive neuromuscular disease, characterized by degeneration of the anterior horn cells of the spinal cord. SMA presents with a highly variable phenotype ranging from very severe to mild (type I-III). No cure for SMA is available at present. All forms of SMA are caused by homozygous loss of the functional survival motor neuron (SMN1) gene. However, all patients have one or more copies of the SMN2 gene, nearly identical to SMN1. Both genes encode the SMN protein but the level produced by SMN2 is insufficient to protect from disease. Increasing SMN2 gene expression could be of considerable therapeutic importance. The aim of this study was to assess whether SMN2 gene expression can be increased by 4-phenylbutyrate (PBA). Fibroblast cell cultures from 16 SMA patients affected by different clinical severities were treated with PBA, and full-length SMN2 transcripts were measured by real-time PCR. In all cell cultures, except one, PBA treatment caused an increase in full-length SMN2 transcripts, ranging from 50 to 160% in type I and from 80 to 400% in type II and III cultures. PBA was found also effective in enhancing SMN protein levels and the number of SMN-containing nuclear structures (gems). These data show that SMN expression is considerably increased by PBA, and suggest that the compound, owing also to its favorable pharmacological properties, could be a good candidate for the treatment of SMA.

Pilot trial of phenylbutyrate in spinal muscular atrophy.

The aim of this study was to evaluate tolerability and efficacy of phenylbutyrate (PB) in patients with spinal muscular atrophy (SMA). Ten patients with SMA type II confirmed by DNA studies (age range 2.6-12.7 years, mean age 6.01) were started on oral PB (triButyrate) in powder or tablets. The dosage was 500 mg/kg per day (maximum dose 19 g/d), divided in five doses (every 4 h, skipping one night-dose) using an intermittent schedule (7 days on and 7 days off). Measures of efficacy were the change in motor function from baseline to 3 and 9 weeks, by means of the Hammersmith functional motor scale. In children older than 5 years, muscle strength, assessed by myometry, and forced vital capacity were also measured. We found a significant increase in the scores of the Hammersmith functional scale between the baseline and both 3-weeks (P < 0.012) and 9-weeks assessments (P < 0.004). Our results indicate that PB might be beneficial to SMA patients without producing any major side effect. Larger prospective randomised, double-blind, placebo controlled trials are needed to confirm these preliminary findings.

SMN transcript levels in leukocytes of SMA patients determined by absolute real-time PCR.

Spinal muscular atrophy (SMA) is an autosomal recessive neuromuscular disorder caused by homozygous mutations of the SMN1 gene. Three forms of SMA are recognized (type I-III) on the basis of clinical severity. All patients have at least one or more (usually 2-4) copies of a highly homologous gene (SMN2), which produces insufficient levels of functional SMN protein, because of alternative splicing of exon 7. Recently, evidence has been provided that SMN2 expression can be enhanced by pharmacological treatment. However, no reliable biomarkers are available to test the molecular efficacy of the treatments. At present, the only potential biomarker is the dosage of SMN products in peripheral blood. However, the demonstration that SMN full-length (SMN-fl) transcript levels are reduced in leukocytes of patients compared with controls remains elusive (except for type I). We have developed a novel assay based on absolute real-time PCR, which allows the quantification of SMN1-fl/SMN2-fl transcripts. For the first time, we have shown that SMN-fl levels are reduced in leukocytes of type II-III patients compared with controls. We also found that transcript levels are related to clinical severity as in type III patients SMN2-fl levels are significantly higher compared with type II and directly correlated with functional ability in type II patients and with age of onset in type III patients. Moreover, in haploidentical siblings with discordant phenotype, the less severely affected individuals showed significantly higher transcript levels. Our study shows that SMN2-fl dosage in leukocytes can be considered a reliable biomarker and can provide the rationale for SMN dosage in clinical trials.

Increased levels of glial cell-derived neurotrophic factor in CSF of infants with SMA.

The cause of motor neuron death in spinal muscular atrophy is still debated. In experimental animal models, neurotrophic factors have great potency in supporting motor neuron survival and differentiation, but there are no clinical studies on neurotrophin involvement in disease progression and motor neuron dysfunction. The aim of this study was to investigate the expression of three neurotrophic factors: nerve growth factor, brain-derived neurotrophic factor, and glial cell-derived neurotrophic factor in the cerebrospinal fluid of six infants with spinal muscular atrophy type I and six controls. The levels of neurotrophic factors were measured using an immunoenzymatic assay. A statistically significant increase in glial cell-derived neurotrophic factor levels was observed in patients with spinal muscular atrophy, compared with controls, whereas nerve growth factor and brain-derived neurotrophic factor did not show significant differences between groups. Glial cell-derived neurotrophic factor is one of the most powerful survival factors for spinal motor neurons. The increase of glial cell-derived neurotrophic factor may represent a response to the loss and damage of neuronal cells at the site of spinal lesion and is possibly related to axonal sprouting and synaptic reorganization of the damaged spinal motor neurons.

The complex interaction between APOE promoter and AD: an Italian case-control study.

The single nucleotide polymorphisms (SNPs) rs449647, rs769446 and rs405509 in the promoter region of the APOE gene have been variously suggested to be epsilon 4-independent risk factors for Alzheimer's disease (AD). A previous Italian study found that the rs449647 was significantly associated with late-onset AD. The aim of this study was to verify whether these APOE promoter SNPs are genetic risk factors for AD and to investigate their interaction with the common APOE polymorphism. A total of 169 clinically diagnosed AD patients and 99 cognitively intact age-matched controls were included in the study. Significant associations with AD independent from sex, age and APOE/epsilon 4 status were found for rs449647 A/A and rs405509 G/G genotypes (positive), and rs449647 A/T and rs405509 T/T genotypes (negative). Haplotype frequency estimation at the APOE locus showed significant associations for the ATG4, ATT4 and ACG3 (positive) and ATT2, ATT3 and TCG3 (negative) haplotypes. Therefore this study confirms the role of the rs449647 A/A genotype as risk factor for AD in Italy and suggests that promoter genotypes and APOE haplotypes might have a complex function in AD-associated genetic risk factors.

Argl6gly polymorphism of the beta2-adrenoceptor gene (ADRBeta2) as a susceptibility factor for nasal polyposis.

BACKGROUND: Nasal polyposis is probably a multifactorial disease, but so far, no genetic susceptibility factor has been identified. The observed associations between the ADRB2 argl6gly polymorphism and asthma-related phenotypes as well as those between nasal polyposis and asthma have prompted us to evaluate the potential involvement of this polymorphism in sinonasal polyposis. METHODS: We enrolled in our study, 56 patients and 47 sex- and age-matched controls. Genomic DNA from cases and controls was extracted and genotype was assessed by a polymerase chain reaction amplification/Nco I digestion assay. Statistical analysis was performed using JMP software (version 5.1). RESULTS: The "number of arg alleles" is significantly higher in cases than in controls (p = 0.0386 at t-test; substantially confirmed by nonparametric tests, p = 0.0396 by Wilcoxon/Kruskal-Wallis tests). CONCLUSION: Although results of this study are preliminary because of the small size of the sample, the arg16 allele seems to be associated with an increased risk of sinonasal polyposis suggesting ADRB2 as a susceptibility gene. This finding, if confirmed, would have a clinical value in helping to assess the genetic risk for sinonasal polyposis thus opening new perspectives for the study of molecular factors underlying the development of nasal polyps.

Expression of the survival of motor neuron (SMN) gene in primary neurons and increase in SMN levels by activation of the N-methyl-D-aspartate glutamate receptor.

Spinal muscular atrophy (SMA) is a common motor neuron degenerative disease caused by mutations of the survival of motor neuron (SMN) gene. The SMN protein is expressed ubiquitously as part of a 300-kilodalton multi-protein complex, incorporating several proteins critically required in pre-mRNA splicing. Although SMN mutations render SMN defective in this role, the specific alpha-motor neuron degenerative phenotype seen in the disease remains unexplained. During the differentiation process of spinal motor neurons and cerebellar granule cells, the acquisition of mature electrophysiological and molecular properties is linked to the activation of the glutamate receptors of N-methyl-D-aspartate (NMDA) subtype. We have used primary cultures of rat cerebellar granules to study SMN expression during neuronal differentiation in vitro and in response to the activation of the NMDA receptor. We report that the expression of gems, the nuclear structures where SMN concentrates, is developmentally regulated. The highest expression is associated with the cell clustering phase and expression of NMDA receptors. Stimulation of the NMDA receptor induces an increase in gem number and in SMN transcription, through activation of its promoter. These results demonstrate that SMN levels are dependent on synaptic activity, implying that SMN may have important neuron-specific functions downstream of synaptic activation.

Apolipoprotein E epsilon4 allele differently affects the patterns of neuropsychological presentation in early- and late-onset Alzheimer's disease patients.

The presence of the apolipoprotein E (APOE) epsilon4 allele is a definite risk factor for the onset of Alzheimer's disease (AD). Its presence seems to affect especially the memory in the early stage of the disease, but the effect on the progression of the disease and survival is still controversial. Some longitudinal studies could be influenced by variables other than APOE, such as the response to medical treatment, rehabilitation therapy and inclusion of patients at different stages of progression at baseline. Moreover, the inclusion in the same study sample of patients of different ages at onset of the disease (below 65 or above 80 years) appears arbitrary. In our study, we evaluated a population of newly diagnosed untreated AD patients at their first neuropsychological examination and with the onset of their first symptoms not longer than 3 years ago. In order to analyse the different effects of the APOE epsilon4 allele on the different ages at the onset of the disease, we split the study sample into two groups: (1) subjects under 65 years [early-onset AD (EOAD); n = 30] and subjects over 70 years [late-onset AD (LOAD); n = 41], excluding subjects with an age of onset between 66 and 69 years. Our results show that the APOE epsilon4 allele carriers are characterised by a different neuropsychological pattern at the disease onset; however, only in the EOAD group is this effect significant: in EOAD, the epsilon4 allele carriers obtained worse performances in learning, long-term verbal memory and general intelligence tasks. On the contrary, in LOAD patients, the pattern of cognitive impairment at the onset is not dependent on the possession of an epsilon4 allele in the genotype. Such data could suggest a careful control of the study sample concerning age at the onset of the disease since APOE could play a different role in EOAD and LOAD mainly due to the different pathogenic mechanism at the onset and evolution of AD.