Loss of DMP1 causes rickets and osteomalacia and identifies a role for osteocytes in mineral metabolism

The osteocyte, a terminally differentiated cell comprising 90%-95% of all bone cells, may have multiple functions, including acting as a mechanosensor in bone (re)modeling. Dentin matrix protein 1 (encoded by DMP1) is highly expressed in osteocytes and, when deleted in mice, results in a hypomineralized bone phenotype. We investigated the potential for this gene not only to direct skeletal mineralization but also to regulate phosphate (P(i)) homeostasis. Both Dmp1-null mice and individuals with a newly identified disorder, autosomal recessive hypophosphatemic rickets, manifest rickets and osteomalacia with isolated renal phosphate-wasting associated with elevated fibroblast growth factor 23 (FGF23) levels and normocalciuria. Mutational analyses showed that autosomal recessive hypophosphatemic rickets family carried a mutation affecting the DMP1 start codon, and a second family carried a 7-bp deletion disrupting the highly conserved DMP1 C terminus. Mechanistic studies using Dmp1-null mice demonstrated that absence of DMP1 results in defective osteocyte maturation and increased FGF23 expression, leading to pathological changes in bone mineralization. Our findings suggest a bone-renal axis that is central to guiding proper mineral metabolism.     

Rescue of a deficiency in ATP synthesis by transfer of MTATP6, a mitochondrial DNA-encoded gene, to the nucleus

A T-->G transversion at nt 8993 in mitochondrial DNA of MTATP6 (encoding ATPase 6 of complex V of the respiratory chain) causes impaired mitochondrial ATP synthesis in two related mitochondrial disorders: neuropathy, ataxia and retinitis pigmentosa and maternally inherited Leigh syndrome. To overcome the biochemical defect, we expressed wildtype ATPase 6 protein allotopically from nucleus-transfected constructs encoding an amino-terminal mitochondrial targeting signal appended to a recoded ATPase 6 gene (made compatible with the universal genetic code) that also contained a carboxy-terminal FLAG epitope tag. After transfection of human cells, the precursor polypeptide was expressed, imported into and processed within mitochondria, and incorporated into complex V. Allotopic expression of stably transfected constructs in cytoplasmic hybrids (cybrids) homoplasmic with respect to the 8993T-->G mutation showed a significantly improved recovery after growth in selective medium as well as a significant increase in ATP synthesis. This is the first successful demonstration of allotopic expression of an mtDNA-encoded polypeptide in mammalian cells and could form the basis of a genetic approach to treat a number of human mitochondrial disorders.     

Turning of nerve growth cones induced by localized increases in intracellular calcium ions

Guidance of developing axons involves turning of the motile tip, the growth cone, in response to a variety of extracellular cues. Little is known about the intracellular mechanism by which the directional signal is transduced. Ca2+ is a key second messenger in growth cone extension and has been implicated in growth-cone turning. Here I report that a direct, spatially restricted elevation of intracellular Ca2+ concentration ([Ca2+]i) on one side of the growth cone by focal laser-induced photolysis (FLIP) of caged Ca2+ consistently induced turning of the growth cone to the side with elevated [Ca2+]i (attraction). Furthermore, when the resting [Ca2+]i at the growth cone was decreased by the removal of extracellular Ca2+, the same focal elevation of [Ca2+]i by FLIP induced repulsion. These results provide direct evidence that a localized Ca2+ signal in the growth cone can provide the intracellular directional cue for extension and is sufficient to initiate both attraction and repulsion. By integrating local and global Ca2+ signals, a growth cone could thus generate different turning responses under different environmental conditions during guidance.     

荷载JQ1/紫杉醇PLGA纳米粒的制备

研究荷载JQ1/紫杉醇PLGA纳米粒的制备,并考察其对黑色素瘤细胞表面PD-L1表达情况的影响。采用乳化溶剂蒸发法制备荷载JQ1/紫杉醇的PLGA纳米粒,并对所制备的纳米粒进行粒径、形貌等理化性质表征;尾静脉注射荷载JQ-1/紫杉醇PLGA纳米粒后,考察大鼠体内的药动学参数;以B16黑色素瘤细胞为模型,应用流式细胞术分析PLGA纳米粒对B16细胞表面PD-L1表达情况的影响。结果表明,所制备的PLGA纳米粒平均粒径为210 nm,其外观呈光滑圆球状。大鼠体内单次静脉注射PLGA纳米粒后,呈二室模型分布,紫杉醇与JQ1主要的药动学参数如下:分布相半衰期为0.142 8、0.169 9 h,消除相半衰期为5.27、2.37 h,血药浓度曲线下面积为8.155、3.793 (μg·h)/mL,清除率为122.612、131.795 mL/(h·kg),表观分布体积为766.07、396.25 mL/kg。流式分析结果表明经PLGA纳米粒组处理后,可降低B16黑色素瘤细胞表面PD-L1的表达。表明所制备的PLGA纳米粒可作为紫杉醇与JQ1两种药物共递送的传输载体,有望提高免疫治疗肿瘤的效果。     

An efficient algorithm for mining closed itemsets

This paper presents a new efficient algorithm for mining frequent closed itemsets. It enumerates the closed set of frequent itemsets by using a novel compound frequent itemset tree that facilitates fast growth and efficient pruning of search space. It also employs a hybrid approach that adapts search strategies, representations of projected transaction subsets, and projecting methods to the characteristics of the dataset. Efficient local pruning, global subsumption checking, and fast hashing methods are detailed in this paper. The principle that balances the overheads of search space growth and pruning is also discussed. Extensive experimental evaluations on real world and artificial datasets showed that our algorithm outperforms CHARM by a factor of five and is one to three orders of magnitude more efficient than CLOSET and MAFIA.     

Subgroup-specific structural variation across 1,000 medulloblastoma genomes

Medulloblastoma, the most common malignant paediatric brain tumour, is currently treated with nonspecific cytotoxic therapies including surgery, whole-brain radiation, and aggressive chemotherapy. As medulloblastoma exhibits marked intertumoural heterogeneity, with at least four distinct molecular variants, previous attempts to identify targets for therapy have been underpowered because of small samples sizes. Here we report somatic copy number aberrations (SCNAs) in 1,087 unique medulloblastomas. SCNAs are common in medulloblastoma, and are predominantly subgroup-enriched. The most common region of focal copy number gain is a tandem duplication of SNCAIP, a gene associated with Parkinson's disease, which is exquisitely restricted to Group 4α. Recurrent translocations of PVT1, including PVT1-MYC and PVT1-NDRG1, that arise through chromothripsis are restricted to Group 3. Numerous targetable SCNAs, including recurrent events targeting TGF-β signalling in Group 3, and NF-κB signalling in Group 4, suggest future avenues for rational, targeted therapy.     

Fitness costs of R-gene-mediated resistance in Arabidopsis thaliana

Resistance genes (R-genes) act as an immune system in plants by recognizing pathogens and inducing defensive pathways. Many R-gene loci are present in plant genomes, presumably reflecting the need to maintain a large repertoire of resistance alleles. These loci also often segregate for resistance and susceptibility alleles that natural selection has maintained as polymorphisms within a species for millions of years. Given the obvious advantage to an individual of being disease resistant, what prevents these resistance alleles from being driven to fixation by natural selection? A cost of resistance is one potential explanation; most models require a lower fitness of resistant individuals in the absence of pathogens for long-term persistence of susceptibility alleles. Here we test for the presence of a cost of resistance at the RPM1 locus of Arabidopsis thaliana. Results of a field experiment comparing the fitness of isogenic strains that differ in the presence or absence of RPM1 and its natural promoter reveal a large cost of RPM1, providing the first evidence that costs contribute to the maintenance of an ancient R-gene polymorphism.     

Hierarchical planning for a surface mounting machine placement

For a surface mounting machine (SMM) in printed circuit board (PCB) assembly line, there are four problems, e.g. CAD data conversion, nozzle selection, feeder assignment and placement sequence determination. A hierarchical planning for them to maximize the throughput rate of an SMM is presented here. To minimize set-up time, a CAD data conversion system was first applied that could automatically generate the data for machine placement from CAD design data files. Then an effective nozzle selection approach implemented to minimize the time of nozzle changing. And then, to minimize picking time, an algorithm for feeder assignment was used to make picking multiple components simultaneously as much as possible. Finally, in order to shorten pick-and-place time, a heuristic algorithm was used to determine optimal component placement sequence according to the decided feeder positions. Experiments were conducted on a four head SMM. The experimental results were used to analyse the assembly line performance.     

Expression and significance of cyclin D1, p27kip1 protein in bronchioloalveolar carcinoma

PURPOSE: To investigate the relationship between expression of cell cycle-related protein cyclin D1, p27kip1 and the pathogenesis of bronchioloalveolar carcinoma (BAC) and the value of prediction of prognosis. METHODS: Cyclin D1 and p27kip1 protein were detected by immunohistochemical En Vision method in 43 BACs. RESULTS: The positivity of cyclin D1 in BAC was 65.1% (28/43), which was significantly higher than that in normal pulmonary tissue (0/13), P<0.01. No statistically significant association was found between cyclin D1 expression data and sex, age, tobacco-use history, histologic subtype (mucinous vs nonmucinous), stromal fibrosis, lymph node metastasis, clinical stage or postoperative survival period (P>0.05), while cyclin D1 expression was found to be negatively correlated with tumor size (P<0.05). The positivity of p27kip1 in BACs was 51.2% (22/43), significantly lower than that in normal pulmonary tissue (12/13), P<0.01. p27kip1 expression level was not associated with sex, age, tobacco-use history, tumor size or histologic subtype (P>0.05), but was negatively correlated with stromal fibrosis, lymph node metastasis and clinical stage (P<0.05); and positively associated with postoperative survival period (P<0.01). The survival rate of p27kip1 positive group was significantly higher than that of p27kip1 negative group (P<0.01). No statistically significant correlation was found between cyclin D1 and p27kip1 expression. CONCLUSIONS: Increased cyclin D1 expression and decreased p27kip1 expression are related to the pathogenesis of BAC; decreased p27kip1 expression is associated with metastasis progression; immunodetection of p27kip1 is useful for assessment of prognosis.