Genetic visualization of notch signaling in mammalian neurogenesis

Notch signaling plays crucial roles in fate determination and the differentiation of neural stem cells in embryonic and adult brains. It is now clear that the notch pathway is under more complex and dynamic regulation than previously thought. To understand the functional details of notch signaling more precisely, it is important to reveal when, where, and how notch signaling is dynamically communicated between cells, for which the visualization of notch signaling is essential. In this review, we introduce recent technical advances in the visualization of notch signaling during neural development and in the adult brain, and we discuss the physiological significance of dynamic regulation of notch signaling.     

Oncogenic mutations of ALK kinase in neuroblastoma

Neuroblastoma in advanced stages is one of the most intractable paediatric cancers, even with recent therapeutic advances. Neuroblastoma harbours a variety of genetic changes, including a high frequency of MYCN amplification, loss of heterozygosity at 1p36 and 11q, and gain of genetic material from 17q, all of which have been implicated in the pathogenesis of neuroblastoma. However, the scarcity of reliable molecular targets has hampered the development of effective therapeutic agents targeting neuroblastoma. Here we show that the anaplastic lymphoma kinase (ALK), originally identified as a fusion kinase in a subtype of non-Hodgkin's lymphoma (NPM-ALK) and more recently in adenocarcinoma of lung (EML4-ALK), is also a frequent target of genetic alteration in advanced neuroblastoma. According to our genome-wide scans of genetic lesions in 215 primary neuroblastoma samples using high-density single-nucleotide polymorphism genotyping microarrays, the ALK locus, centromeric to the MYCN locus, was identified as a recurrent target of copy number gain and gene amplification. Furthermore, DNA sequencing of ALK revealed eight novel missense mutations in 13 out of 215 (6.1%) fresh tumours and 8 out of 24 (33%) neuroblastoma-derived cell lines. All but one mutation in the primary samples (12 out of 13) were found in stages 3-4 of the disease and were harboured in the kinase domain. The mutated kinases were autophosphorylated and displayed increased kinase activity compared with the wild-type kinase. They were able to transform NIH3T3 fibroblasts as shown by their colony formation ability in soft agar and their capacity to form tumours in nude mice. Furthermore, we demonstrate that downregulation of ALK through RNA interference suppresses proliferation of neuroblastoma cells harbouring mutated ALK. We anticipate that our findings will provide new insights into the pathogenesis of advanced neuroblastoma and that ALK-specific kinase inhibitors might improve its clinical outcome.     

Thyrotrophin in the pars tuberalis triggers photoperiodic response

Molecular mechanisms regulating animal seasonal breeding in response to changing photoperiod are not well understood. Rapid induction of gene expression of thyroid-hormone-activating enzyme (type 2 deiodinase, DIO2) in the mediobasal hypothalamus (MBH) of the Japanese quail (Coturnix japonica) is the earliest event yet recorded in the photoperiodic signal transduction pathway. Here we show cascades of gene expression in the quail MBH associated with the initiation of photoinduced secretion of luteinizing hormone. We identified two waves of gene expression. The first was initiated about 14 h after dawn of the first long day and included increased thyrotrophin (TSH) beta-subunit expression in the pars tuberalis; the second occurred approximately 4 h later and included increased expression of DIO2. Intracerebroventricular (ICV) administration of TSH to short-day quail stimulated gonadal growth and expression of DIO2 which was shown to be mediated through a TSH receptor-cyclic AMP (cAMP) signalling pathway. Increased TSH in the pars tuberalis therefore seems to trigger long-day photoinduced seasonal breeding.     

p53-induced inhibition of Hif-1 causes cardiac dysfunction during pressure overload

Cardiac hypertrophy occurs as an adaptive response to increased workload to maintain cardiac function. However, prolonged cardiac hypertrophy causes heart failure, and its mechanisms are largely unknown. Here we show that cardiac angiogenesis is crucially involved in the adaptive mechanism of cardiac hypertrophy and that p53 accumulation is essential for the transition from cardiac hypertrophy to heart failure. Pressure overload initially promoted vascular growth in the heart by hypoxia-inducible factor-1 (Hif-1)-dependent induction of angiogenic factors, and inhibition of angiogenesis prevented the development of cardiac hypertrophy and induced systolic dysfunction. Sustained pressure overload induced an accumulation of p53 that inhibited Hif-1 activity and thereby impaired cardiac angiogenesis and systolic function. Conversely, promoting cardiac angiogenesis by introducing angiogenic factors or by inhibiting p53 accumulation developed hypertrophy further and restored cardiac dysfunction under chronic pressure overload. These results indicate that the anti-angiogenic property of p53 may have a crucial function in the transition from cardiac hypertrophy to heart failure.     

芯片调试技术中插入点和监听电路区域的研究

根据硬件开销和缺陷的检测能力评估了一种可重构的调试设计方案.对于要调试的目标电路,首先设计并完成了一套由4个32位处理器核组成的多处理机系统,然后评估该调试设计电路的硬件架构.对改变调试电路排列的评估结果表明,调试电路的硬件开销占用所实现的多处理机系统在8.6%～12.7%的范围内.其次,对是否可以通过调试电路发现故障效应进行了评估.在一个16位处理器核上注入了10种不同的故障并且检查其是否会被每一个设置在处理器核上的观测点所发现,同时测量了观察所需的时钟周期数.最后还评估了每一种故障的可观察率以及每一个观察点的可观察率.     

Reduced deformability of erythrocytes exposed to hypercapnia

Summary The effect of hypercapnia on the deformability of erythrocytes was studied by means of a nuclepore membrane filter method. A decrement of the deformability by 20–40% was observed when was increased from 50 mm Hg to 200 mm Hg, accompanied with an increment of 5% in hematocrit value.     

Crystal structure of a stable dimer reveals the molecular basis of serpin polymerization

Repeating intermolecular protein association by means of beta-sheet expansion is the mechanism underlying a multitude of diseases including Alzheimer's, Huntington's and Parkinson's and the prion encephalopathies. A family of proteins, known as the serpins, also forms large stable multimers by ordered beta-sheet linkages leading to intracellular accretion and disease. These 'serpinopathies' include early-onset dementia caused by mutations in neuroserpin, liver cirrhosis and emphysema caused by mutations in alpha(1)-antitrypsin (alpha(1)AT), and thrombosis caused by mutations in antithrombin. Serpin structure and function are quite well understood, and the family has therefore become a model system for understanding the beta-sheet expansion disorders collectively known as the conformational diseases. To develop strategies to prevent and reverse these disorders, it is necessary to determine the structural basis of the intermolecular linkage and of the pathogenic monomeric state. Here we report the crystallographic structure of a stable serpin dimer which reveals a domain swap of more than 50 residues, including two long antiparallel beta-strands inserting in the centre of the principal beta-sheet of the neighbouring monomer. This structure explains the extreme stability of serpin polymers, the molecular basis of their rapid propagation, and provides critical new insights into the structural changes which initiate irreversible beta-sheet expansion.