脊肌萎缩症研究进展

脊肌萎缩症是一组常见的引起婴幼儿死亡的遗传病, 因为缺乏治疗手段,该病研究曾不受重视。自1995年确定脊肌萎缩症致病基因是一种看家基因---运动神经元生存基因（SMN1）以来,围绕在这种疾病背后的谜团吸引了多国学者的兴趣,成为近年遗传病研究的一个热点,本文就脊肌萎缩症遗传基础,SMN蛋白生物功能,脊肌萎缩症携带者检测及治疗方面新策略等内容做一综述。     

脊肌萎缩症研究进展

脊肌萎缩症是一组常见的引起婴幼儿死亡的遗传病,因为缺乏治疗手段,该病研究曾不受重视.自1995年确定脊肌萎缩症致病基因是一种看家基因--运动神经元生存基因(SMN1)以来,围绕在这种疾病背后的谜团吸引了多国学者的兴趣,成为近年遗传病研究的一个热点,本文就脊肌萎缩症遗传基础,SMN蛋白生物功能,脊肌萎缩症携带者检测及治疗方面新策略等内容作一综述.     

脊肌萎缩症研究进展

脊肌萎缩症是一组常见的引起婴幼儿死亡的遗传病,因为缺乏治疗手段,该病研究曾不受重视.自1995年确定脊肌萎缩症致病基因是一种看家基因--运动神经元生存基因(SMN1)以来,围绕在这种疾病背后的谜团吸引了多国学者的兴趣,成为近年遗传病研究的一个热点,本文就脊肌萎缩症遗传基础,SMN蛋白生物功能,脊肌萎缩症携带者检测及治疗方面新策略等内容作一综述.     

脊肌萎缩症研究进展

脊肌萎缩症是一组常见的引起婴幼儿死亡的遗传病,因为缺乏治疗手段,该病研究曾不受重视.自1995年确定脊肌萎缩症致病基因是一种看家基因--运动神经元生存基因(SMN1)以来,围绕在这种疾病背后的谜团吸引了多国学者的兴趣,成为近年遗传病研究的一个热点,本文就脊肌萎缩症遗传基础,SMN蛋白生物功能,脊肌萎缩症携带者检测及治疗方面新策略等内容作一综述.     

脊肌萎缩症研究进展

脊肌萎缩症是一组常见的引起婴幼儿死亡的遗传病,因为缺乏治疗手段,该病研究曾不受重视.自1995年确定脊肌萎缩症致病基因是一种看家基因--运动神经元生存基因(SMN1)以来,围绕在这种疾病背后的谜团吸引了多国学者的兴趣,成为近年遗传病研究的一个热点,本文就脊肌萎缩症遗传基础,SMN蛋白生物功能,脊肌萎缩症携带者检测及治疗方面新策略等内容作一综述.     

脊肌萎缩症研究进展

脊肌萎缩症是一组常见的引起婴幼儿死亡的遗传病,因为缺乏治疗手段,该病研究曾不受重视.自1995年确定脊肌萎缩症致病基因是一种看家基因--运动神经元生存基因(SMN1)以来,围绕在这种疾病背后的谜团吸引了多国学者的兴趣,成为近年遗传病研究的一个热点,本文就脊肌萎缩症遗传基础,SMN蛋白生物功能,脊肌萎缩症携带者检测及治疗方面新策略等内容作一综述.     

脊肌萎缩症研究进展

脊肌萎缩症是一组常见的引起婴幼儿死亡的遗传病,因为缺乏治疗手段,该病研究曾不受重视.自1995年确定脊肌萎缩症致病基因是一种看家基因--运动神经元生存基因(SMN1)以来,围绕在这种疾病背后的谜团吸引了多国学者的兴趣,成为近年遗传病研究的一个热点,本文就脊肌萎缩症遗传基础,SMN蛋白生物功能,脊肌萎缩症携带者检测及治疗方面新策略等内容作一综述.     

脊肌萎缩症研究进展

脊肌萎缩症是一组常见的引起婴幼儿死亡的遗传病,因为缺乏治疗手段,该病研究曾不受重视.自1995年确定脊肌萎缩症致病基因是一种看家基因--运动神经元生存基因(SMN1)以来,围绕在这种疾病背后的谜团吸引了多国学者的兴趣,成为近年遗传病研究的一个热点,本文就脊肌萎缩症遗传基础,SMN蛋白生物功能,脊肌萎缩症携带者检测及治疗方面新策略等内容作一综述.     

脊肌萎缩症研究进展

脊肌萎缩症是一组常见的引起婴幼儿死亡的遗传病,因为缺乏治疗手段,该病研究曾不受重视.自1995年确定脊肌萎缩症致病基因是一种看家基因--运动神经元生存基因(SMN1)以来,围绕在这种疾病背后的谜团吸引了多国学者的兴趣,成为近年遗传病研究的一个热点,本文就脊肌萎缩症遗传基础,SMN蛋白生物功能,脊肌萎缩症携带者检测及治疗方面新策略等内容作一综述.     

脊肌萎缩症研究进展

脊肌萎缩症是一组常见的引起婴幼儿死亡的遗传病,因为缺乏治疗手段,该病研究曾不受重视.自1995年确定脊肌萎缩症致病基因是一种看家基因--运动神经元生存基因(SMN1)以来,围绕在这种疾病背后的谜团吸引了多国学者的兴趣,成为近年遗传病研究的一个热点,本文就脊肌萎缩症遗传基础,SMN蛋白生物功能,脊肌萎缩症携带者检测及治疗方面新策略等内容作一综述.     

The distribution of SMN protein complex in human fetal tissues and its alteration in spinal muscular atrophy

Spinal muscular atrophy (SMA) is a common autosomal recessive neuromuscular disorder characterized by degeneration of motor neurons of the spinal cord and muscular atrophy. SMA is caused by alterations to the survival of motor neuron (SMN) gene, the function of which has hitherto been unclear. Here, we present immunoblot analyses showing that normal SMN protein expression undergoes a marked decay in the postnatal period compared with fetal development. Morphological and immunohistochemical analyses of the SMN protein in human fetal tissues showed a general distribution in the cytoplasm, except in muscle cells, where SMN protein was immunolocalized to large cytoplasmic dot-like structures and was tightly associated with membrane-free heavy sedimenting complexes. These cytoplasmic structures were similar in size to gem. The SMN protein was markedly deficient in tissues derived from type I SMA fetuses, including skeletal muscles and, as previously shown, spinal cord. While our data do not help decide whether SMA results from impaired SMN expression in spinal cord, skeletal muscle or both, they suggest a requirement for SMN protein during embryo-fetal development.      

The spinal muscular atrophy disease protein SMN is linked to the Rho-kinase pathway via profilin

Spinal muscular atrophy (SMA), a frequent neurodegenerative disease, is caused by reduced levels of functional survival of motoneuron (SMN) protein. SMN is involved in multiple pathways, including RNA metabolism and splicing as well as motoneuron development and function. Here we provide evidence for a major contribution of the Rho-kinase (ROCK) pathway in SMA pathogenesis. Using an in vivo protein interaction system based on SUMOylation of proteins, we found that SMN is directly interacting with profilin2a. Profilin2a binds to a stretch of proline residues in SMN, which is heavily impaired by a novel SMN2 missense mutation (S230L) derived from a SMA patient. In different SMA models, we identified differential phosphorylation of the ROCK-downstream targets cofilin, myosin-light chain phosphatase and profilin2a. We suggest that hyper-phosphorylation of profilin2a is the molecular link between SMN and the ROCK pathway repressing neurite outgrowth in neuronal cells. Finally, we found a neuron-specific increase in the F-/G-actin ratio that further support the role of actin dynamics in SMA pathogenesis.     

The RNA-binding properties of SMN: deletion analysis of the zebrafish orthologue defines domains conserved in evolution

Spinal muscular atrophy (SMA) is a common autosomal recessive disorder that results in the degeneration of spinal motor neurons. SMA is caused by alterations of the survival motor neuron ( SMN ) gene which encodes a novel protein of hitherto unclear function. The SMN protein associates with ribonucleoprotein particles involved in RNA processing and exhibits an RNA-binding capacity. We have isolated the zebrafish Danio rerio and nematode Caenorhabditis elegans orthologues and have found that the RNA-binding capacity is conserved across species. Purified recombinant SMN proteins from both species showed selectivity to poly(G) homopolymer RNA in vitro, similar to that of the human protein. Studying deletions of the zebrafish SMN protein, we defined an RNA-binding element in exon 2a, which is highly conserved across species, and revealed that its binding activity is modulated by protein domains encoded by exon 2b and exon 3. Finally, the deleted recombinant zebrafish protein mimicking an SMA frameshift mutation showed a dramatic change in vitro in the formation of the RNA-protein complexes. These observations indicate that the RNA-binding capacity of SMN is an evolutionarily conserved function and further support the view that defects in RNA metabolism most likely account for the pathogenesis of SMA.     

Increased susceptibility of spinal muscular atrophy fibroblasts to camptothecin-induced cell death

Spinal muscular atrophy (SMA) is a neuromuscular disease caused by deletions or mutations in the telomeric copy of the survival motor neuron (SMN1) gene. Although the SMN protein has been implicated in the biogenesis of ribonucleoprotein complexes and RNA processing, it is not clear how these functions contribute to the pathogenesis of SMA. To gain a further understanding of SMN function, we have investigated its role in cell survival in skin fibroblasts derived from SMA patients and age-matched controls. SMA fibroblasts exposed to camptothecin, a specific inhibitor of DNA topoisomerase I, consistently showed cell death at a lower concentration than normal controls. Treatment with other cell death-inducing agents did not cause differences in survival of SMA fibroblasts as compared with control fibroblasts. Camptothecin treatment resulted in activation of caspase-3 with generation of the caspase-3 cleavage product, poly ADP-ribose polymerase (PARP). Depletion of SMN protein by RNA interference in control fibroblasts increased caspase-3 activity, whereas transfection of SMA fibroblasts with wild-type SMN decreased caspase-3 activity. Our data demonstrate that SMA fibroblasts are more prone to some, but not all, death-stimuli. Vulnerability to death-stimuli is associated with decreased levels of SMN protein and is mediated by activation of caspase-3.     

The exon 2b region of the spinal muscular atrophy protein, SMN, is involved in self-association and SIP1 binding

Spinal muscular atrophy (SMA) is caused by mutations in the SMN (survival of motor neurons) gene and there is a correlation between disease severity and levels of functional SMN protein. Studies of structure-function relationships in SMN protein may lead to a better understanding of SMA pathogenesis. Self-association of the spinal muscular atrophy protein, SMN, is important for its function in RNA splicing. Biomolecular interaction analysis core analysis now shows that SMN self-association occurs via SMN regions encoded by exons 2b and 6, that exon 2b encodes a binding site for SMN-interacting protein-1 and that interaction occurs between exon 2- and 4-encoded regions within the SMN monomer. The presence of two separate self-association sites suggests a novel mechanism by which linear oligomers or closed rings might be formed from SMN monomers.     

Refined characterization of the expression and stability of the SMN gene products

Spinal muscular atrophy (SMA) is characterized by degeneration of lower motor neurons and caused by mutations of the SMN1 gene. SMN1 is duplicated in a homologous gene called SMN2, which remains present in patients. SMN has an essential role in RNA metabolism, but its role in SMA pathogenesis remains unknown. Previous studies suggested that in neurons the protein lacking the C terminus (SMN(Delta7)), the major product of the SMN2 gene, had a dominant-negative effect. We generated antibodies specific to SMN(FL) or SMN(Delta7). In transfected cells, the stability of the SMN(Delta7) protein was regulated in a cell-dependent manner. Importantly, whatever the human tissues examined, SMN(Delta7) protein was undetectable because of the instability of the protein, thus excluding a dominant effect of SMN(Delta7) in SMA. A similar decreased level of SMN(FL) was observed in brain and spinal cord samples from human SMA, suggesting that SMN(FL) may have specific targets in motor neurons. Moreover, these data indicate that the vulnerability of motor neurons cannot simply be ascribed to the differential expression or a more dramatic reduction of SMN(FL) in spinal cord when compared with brain tissue. Improving the stability of SMN(Delta7) protein might be envisaged as a new therapeutic strategy in SMA.     

The role of the SMN gene in proximal spinal muscular atrophy

Childhood spinal muscular atrophy (SMA) is a common recessive autosomal disorder that results in degeneration of lower motor neurons. The identification of the disease gene, Survival of Motor Neuron (SMN), was a major advance in understanding the molecular basis underlying this devastating neuromuscular disease. This finding has greatly improved the genetic counselling of SMA families. Recently, biochemical studies demonstrated its involvement in the biogenesis of spliceosomal snRNPs, suggesting a critical role of SMN in RNA processing. Surprisingly, other studies showed a putative role of SMN in an anti-apoptotic pathway involving Bcl-2. The function of SMN protein is not fully understood. These observations emphasized the difficulty in elucidating the function of any novel protein. Therefore, multidisciplinary approaches are required to understand the pathogenesis of SMA.