Preferential deletion of exons in Duchenne and Becker muscular dystrophies

Duchenne and Becker muscular dystrophy (DMD and BMD) genes are located in Xp21 on the short arm of the X chromosome. DMD patients display a much more severe clinical course than BMD patients, and yet about 10% of cases of each have been reported to have deletions for parts of the gene. Using a complementary DNA subclone of the DMD gene we have screened 66 DMD and BMD patients who had not previously shown deletions with the probes then available. Fifteen patients have a deletion of this part of the gene, indicating a higher deletion frequency in this region (22%). Exons were deleted in five severely affected DMD patients and in ten BMD patients. Significantly, most of these deletions begin in the same region of the cDNA, which implies that there is a common mechanism for the generation of many of these mutations. An apparently identical deletion in one family gave classical BMD in two brothers (presenting in their teens) and only very mild muscle weakness in their 86-year-old great-great-uncle. Taking these data together with data using the probes previously published, we are able to detect deletions directly in 40% of our families requiring antenatal diagnosis or carrier detection.     

Deletion of brain dystroglycan recapitulates aspects of congenital muscular dystrophy

Fukuyama congenital muscular dystrophy (FCMD), muscle-eye-brain disease (MEB), and Walker-Warburg syndrome are congenital muscular dystrophies (CMDs) with associated developmental brain defects. Mutations reported in genes of FCMD and MEB patients suggest that the genes may be involved in protein glycosylation. Dystroglycan is a highly glycosylated component of the muscle dystrophin-glycoprotein complex that is also expressed in brain, where its function is unknown. Here we show that brain-selective deletion of dystroglycan in mice is sufficient to cause CMD-like brain malformations, including disarray of cerebral cortical layering, fusion of cerebral hemispheres and cerebellar folia, and aberrant migration of granule cells. Dystroglycan-null brain loses its high-affinity binding to the extracellular matrix protein laminin, and shows discontinuities in the pial surface basal lamina (glia limitans) that probably underlie the neuronal migration errors. Furthermore, mutant mice have severely blunted hippocampal long-term potentiation with electrophysiologic characterization indicating that dystroglycan might have a postsynaptic role in learning and memory. Our data strongly support the hypothesis that defects in dystroglycan are central to the pathogenesis of structural and functional brain abnormalities seen in CMD.     

An agrin minigene rescues dystrophic symptoms in a mouse model for congenital muscular dystrophy

Congenital muscular dystrophy is a heterogeneous and severe, progressive muscle-wasting disease that frequently leads to death in early childhood. Most cases of congenital muscular dystrophy are caused by mutations in LAMA2, the gene encoding the alpha2 chain of the main laminin isoforms expressed by muscle fibres. Muscle fibre deterioration in this disease is thought to be caused by the failure to form the primary laminin scaffold, which is necessary for basement membrane structure, and the missing interaction between muscle basement membrane and the dystrophin-glycoprotein complex (DGC) or the integrins. With the aim to restore muscle function in a mouse model for this disease, we have designed a minigene of agrin, a protein known for its role in the formation of the neuromuscular junction. Here we show that this mini-agrin-which binds to basement membrane and to alpha-dystroglycan, a member of the DGC-amends muscle pathology by a mechanism that includes agrin-mediated stabilization of alpha-dystroglycan and the laminin alpha5 chain. Our data provides in vivo evidence that a non-homologous protein in combination with rational protein design can be used to devise therapeutic tools that may restore muscle function in human muscular dystrophies.     

神经退行性疾病相关蛋白的翻译后修饰

特定靶蛋白的翻译后修饰对其执行细胞功能有重要作用,是细胞对生长、分化和应激等信号刺激所产生的调节功能的一种反应.翻译后修饰包括磷酸化修饰、乙酰化、甲基化、泛素化、类泛素化等不同的修饰.在神经退行性疾病的研究中,翻译后修饰对疾病的发生和病理影响日益受到人们的重视,我们对磷酸化、泛素化和类泛素化(SUMO化)修饰与神经退行疾病的关系及本实验室的工作进行介绍.     

微藻细胞破壁方法研究进展

微藻具有光合作用效率高、环境适应性强、生长快、生物质产率高和环境效益显著等优点,在体内还能积累虾青素、叶黄素、高不饱和脂肪酸、生物柴油等重要产物,近年来成为人们关注和研究的热点。微藻细胞破壁是提取这些产物的关键及困难环节。从3种常用微藻细胞壁的结构入手,分析总结了机械破壁法、基于波的细胞破壁法、热解破壁法、化学法以及生物法等微藻破壁技术的研究现状与发展趋势。认为从现实角度出发,将化学法与机械法结合使用,即先采用化学法进行预处理,再采用机械法破壁,可解决大部分藻细胞的破壁问题,是一种比较可行的产业化破壁技术路线;从发展前景来看,生物法破壁具有能量消耗较低、条件温和等优势,对于绝大多数藻类来说具有经济可行性和技术理论可行性,是一种最值得期待的破壁方法。     

钨在等离子体破裂时的表面损伤

在托卡马克类型的聚变装置中,面向等离子体材料在等离子体破裂过程中要承受剧烈的热负荷,这会使得面向等离子体材料表面受到严重的损伤。实验中将纯钨样品放入HT-7托卡马克的刮削层中,以研究等离子体与纯钨表面的作用。实验后发现样品表面产生了等离子体冲击痕和熔化斑痕。     

Defective membrane repair in dysferlin-deficient muscular dystrophy

Muscular dystrophy includes a diverse group of inherited muscle diseases characterized by wasting and weakness of skeletal muscle. Mutations in dysferlin are linked to two clinically distinct muscle diseases, limb-girdle muscular dystrophy type 2B and Miyoshi myopathy, but the mechanism that leads to muscle degeneration is unknown. Dysferlin is a homologue of the Caenorhabditis elegans fer-1 gene, which mediates vesicle fusion to the plasma membrane in spermatids. Here we show that dysferlin-null mice maintain a functional dystrophin-glycoprotein complex but nevertheless develop a progressive muscular dystrophy. In normal muscle, membrane patches enriched in dysferlin can be detected in response to sarcolemma injuries. In contrast, there are sub-sarcolemmal accumulations of vesicles in dysferlin-null muscle. Membrane repair assays with a two-photon laser-scanning microscope demonstrated that wild-type muscle fibres efficiently reseal their sarcolemma in the presence of Ca2+. Interestingly, dysferlin-deficient muscle fibres are defective in Ca2+-dependent sarcolemma resealing. Membrane repair is therefore an active process in skeletal muscle fibres, and dysferlin has an essential role in this process. Our findings show that disruption of the muscle membrane repair machinery is responsible for dysferlin-deficient muscle degeneration, and highlight the importance of this basic cellular mechanism of membrane resealing in human disease.     

Post-translational insertion of a fragment of the glucose transporter into microsomes requires phosphoanhydride bond cleavage

Most eukaryotic secretory and membrane proteins insert co-translationally into the membrane of the rough endoplasmic reticulum (RER), and are targeted there by one or more NH2-terminal or internal signal sequences. However, little is known about the actual translocation and membrane integration processes. In particular, any energy requirements for targeting and integration have remained obscure because of the inability to uncouple the processes from concomitant protein synthesis. We recently showed that the human glucose transporter (GT), an integral membrane glycoprotein, can insert post-translationally into dog pancreatic microsomes with low but demonstrable efficiency in vitro, and that a fragment corresponding to the NH2-terminal 340 amino acids and 8 of the 12 membrane-spanning alpha-helixes of GT (GT-N) can insert with significantly greater efficiency. We report here that post-translational insertion of GT-N into pancreatic microsomes requires energy in the form of a phosphodiester bond, and suggest that co-translational insertion of proteins into the RER may also require energy independent of that used for polypeptide synthesis.     

需求突变情况下的双渠道供应链协调

研究了在直销和通过零售商的传统销售渠道共存的物流服务模式下,一个生产商和一个零售商的协调关系.以最大化供应商的总利润为目标,在假定需求是价格的线性函数的前提下,研究传统供应链需求突变对整个供应链的影响,以及如何通过改变直销链的价格策略来影响供应链的需求,从而实现整个供应网络的供需协调,并为生产商提供了需求突变下的解决方案.最后对契约模型进行了数值仿真分析,给出了契约的选择及参数的求解方法.研究结果表明,在突变程度和成本满足一定的关系时,生产商可以利用直销链来应对零售商需求订单的突变,反之,生产商会选择与零售商改变契约,来共同应对需求突变.     

Efficient disruption of small asteroids by Earth's atmosphere

Accurate modelling of the interaction between the atmosphere and an incoming bolide is a complex task, but crucial to determining the fraction of small asteroids that actually hit the Earth's surface. Most semi-analytical approaches have simplified the problem by considering the impactor as a strengthless liquid-like object ('pancake' models), but recently a more realistic model has been developed that calculates motion, aerodynamic loading and ablation for each separate particle or fragment in a disrupted impactor. Here we report the results of a large number of simulations in which we use both models to develop a statistical picture of atmosphere-bolide interaction for iron and stony objects with initial diameters up to approximately 1 km. We show that the separated-fragments model predicts the total atmospheric disruption of much larger stony bodies than previously thought. In addition, our data set of >1,000 simulated impacts, combined with the known pre-atmospheric flux of asteroids with diameters less than 1 km, elucidates the flux of small bolides at the Earth's surface. We estimate that bodies >220 m in diameter will impact every 170,000 years.     

基于需求数量突变的供应链协调

研究由一个制造商和一个销售商组成的二级供应链在需求数量突变时的协调.分析了常规运作下、需求数量突变下集成供应链的收益和分散供应链各企业的收益.应用Shapley值法进行需求数量突变时收益的再分配,有效地解决了个体理性和集体理性的冲突,达到了供应链协调的目的.