RNAi-mediated gene silencing in non-human primates

The opportunity to harness the RNA interference (RNAi) pathway to silence disease-causing genes holds great promise for the development of therapeutics directed against targets that are otherwise not addressable with current medicines. Although there are numerous examples of in vivo silencing of target genes after local delivery of small interfering RNAs (siRNAs), there remain only a few reports of RNAi-mediated silencing in response to systemic delivery of siRNA, and there are no reports of systemic efficacy in non-rodent species. Here we show that siRNAs, when delivered systemically in a liposomal formulation, can silence the disease target apolipoprotein B (ApoB) in non-human primates. APOB-specific siRNAs were encapsulated in stable nucleic acid lipid particles (SNALP) and administered by intravenous injection to cynomolgus monkeys at doses of 1 or 2.5 mg kg(-1). A single siRNA injection resulted in dose-dependent silencing of APOB messenger RNA expression in the liver 48 h after administration, with maximal silencing of >90%. This silencing effect occurred as a result of APOB mRNA cleavage at precisely the site predicted for the RNAi mechanism. Significant reductions in ApoB protein, serum cholesterol and low-density lipoprotein levels were observed as early as 24 h after treatment and lasted for 11 days at the highest siRNA dose, thus demonstrating an immediate, potent and lasting biological effect of siRNA treatment. Our findings show clinically relevant RNAi-mediated gene silencing in non-human primates, supporting RNAi therapeutics as a potential new class of drugs.     

高容量温盘驱动器伺服码同步时钟录写技术

提出了可变频时钟写入方法和锁相环倍频时钟写入方法，给出了这两种写入法的读／写电路，并分析了其性能。结果证明，可变频时钟写入方法电路简单，刻写时钟周期短；锁相环倍频时钟写入过程较前者长，但其频率范围容易调整。两者均适合高密度小型温盘的时钟录写。     

The ELF3 zeitnehmer regulates light signalling to the circadian clock

The circadian system regulates 24-hour biological rhythms and seasonal rhythms, such as flowering. Long-day flowering plants like Arabidopsis thaliana, measure day length with a rhythm that is not reset at lights-off, whereas short-day plants measure night length on the basis of circadian rhythm of light sensitivity that is set from dusk, early flowering 3 (elf3) mutants of Arabidopsis are aphotoperiodic and exhibit light-conditional arrhythmias. Here we show that the elf3-7 mutant retains oscillator function in the light but blunts circadian gating of CAB gene activation, indicating that deregulated phototransduction may mask rhythmicity. Furthermore, elf3 mutations confer the resetting pattern of short-day photoperiodism, indicating that gating of phototransduction may control resetting. Temperature entrainment can bypass the requirement for normal ELF3 function for the oscillator and partially restore rhythmic CAB expression. Therefore, ELF3 specifically affects light input to the oscillator, similar to its function in gating CAB activation, allowing oscillator progression past a light-sensitive phase in the subjective evening. ELF3 provides experimental demonstration of the zeitnehmer ('time-taker') concept.     

Inactivation of the apoptosis effector Apaf-1 in malignant melanoma

Metastatic melanoma is a deadly cancer that fails to respond to conventional chemotherapy and is poorly understood at the molecular level. p53 mutations often occur in aggressive and chemoresistant cancers but are rarely observed in melanoma. Here we show that metastatic melanomas often lose Apaf-1, a cell-death effector that acts with cytochrome c and caspase-9 to mediate p53-dependent apoptosis. Loss of Apaf-1 expression is accompanied by allelic loss in metastatic melanomas, but can be recovered in melanoma cell lines by treatment with the methylation inhibitor 5-aza-2'-deoxycytidine (5aza2dC). Apaf-1-negative melanomas are invariably chemoresistant and are unable to execute a typical apoptotic programme in response to p53 activation. Restoring physiological levels of Apaf-1 through gene transfer or 5aza2dC treatment markedly enhances chemosensitivity and rescues the apoptotic defects associated with Apaf-1 loss. We conclude that Apaf-1 is inactivated in metastatic melanomas, which leads to defects in the execution of apoptotic cell death. Apaf-1 loss may contribute to the low frequency of p53 mutations observed in this highly chemoresistant tumour type.     

The p53 tumour suppressor gene

The cell cycle is composed of a series of steps which can be negatively or positively regulated by various factors. Chief among the negative regulators is the p53 protein. Alteration or inactivation of p53 by mutation, or by its interactions with oncogene products of DNA tumour viruses, can lead to cancer. These mutations seem to be the most common genetic change in human cancers.     

Partial deficiency of erythrocyte spectrin in hereditary spherocytosis

Hereditary spherocytosis (HS) is a common, clinically heterogeneous haemolytic anaemia in which the primary erythrocyte defect is believed to be some abnormality in the spectrin-actin membrane skeleton, leading to loss of surface membrane. Recessively inherited spectrin deficiency with extreme erythrocyte fragility and spherocytosis has been identified in certain mutant mice and two severely anaemic humans. Although suspected, deficiency of spectrin has not been demonstrated in less severe forms of human HS. We not report the quantitation of erythrocytes spectrin by radioimmunoassay. We found that normal erythrocytes contained 240,000 copies of spectrin heterodimer, whereas erythrocytes from 14 patients with a variety of types of HS were all partially deficient in spectrin (range 74,000-200,000 copies), the magnitude of the deficiency correlating with the severity of the disease. Spectrin deficiency of varying degrees is common in HS and probably represents the principal structural defect leading to loss of surface membrane.     

嵌套式建模支持

阐述了人的建模思维机制。引入等价关系和划分作为问题粒度研究的基础，定义了逆商集，使之与商集一起，构成了对问题不同粒度的完整描述，并讨论了粒度的性质，借助拓扑分析，给出了问题可分解、可细化和粗化、细化等一系列定义，在问题簇和模型簇概念的基础上，提出了嵌套式建模（支持）作为面向复杂系统的建模支持方法论，具体给出了其实施步骤，这是一个人机交互的启发式过程，将嵌套式建模与传统式建模作了比较，此外还作了若干说明。     

A general model for ontogenetic growth.

Several equations have been proposed to describe ontogenetic growth trajectories for organisms justified primarily on the goodness of fit rather than on any biological mechanism. Here, we derive a general quantitative model based on fundamental principles for the allocation of metabolic energy between maintenance of existing tissue and the production of new biomass. We thus predict the parameters governing growth curves from basic cellular properties and derive a single parameterless universal curve that describes the growth of many diverse species. The model provides the basis for deriving allometric relationships for growth rates and the timing of life history events.     

Direct detection of more than 50% of the Duchenne muscular dystrophy mutations by field inversion gels

Duchenne muscular dystrophy (DMD) is an X-linked disorder affecting about 1 in 3,500 males. It is allelic with the milder Becker muscular dystrophy. The biochemical basis for both diseases is unknown and no effective treatment is available. Long-range physical mapping has shown that the DMD gene, localized in Xp21, is extremely large, exceeding 2 million base pairs. Until now, carrier detection and prenatal diagnosis has involved the use of linked restriction fragment length polymorphism markers which detect muscular dystrophy-associated deletions in about 10% of the cases. Field inversion gel electrophoresis (FIGE) allows the detection of structural rearrangements in 21 out of 39 of the DMD patients studied (54%), of which 14 (65%) were not detected by conventional methods. Large deletions seem to make up a much higher fraction of the DMD mutations than so far indicated by other methods. A region prone to deletion was located in the distal half of the gene. FIGE analysis could provide a valuable extension of information for carrier detection and prenatal diagnosis. The technique should be generally applicable to the study of diseases involving structural chromosomal rearrangements.