共查询到20条相似文献,搜索用时 0 毫秒
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Coudreuse DY Roël G Betist MC Destrée O Korswagen HC 《Science (New York, N.Y.)》2006,312(5775):921-924
Wnt proteins function as morphogens that can form long-range concentration gradients to pattern developing tissues. Here, we show that the retromer, a multiprotein complex involved in intracellular protein trafficking, is required for long-range signaling of the Caenorhabditis elegans Wnt ortholog EGL-20. The retromer functions in EGL-20-producing cells to allow the formation of an EGL-20 gradient along the anteroposterior axis. This function is evolutionarily conserved, because Wnt target gene expression is also impaired in the absence of the retromer complex in vertebrates. These results demonstrate that the ability of Wnt to regulate long-range patterning events is dependent on a critical and conserved function of the retromer complex within Wnt-producing cells. 相似文献
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Inamori K Yoshida-Moriguchi T Hara Y Anderson ME Yu L Campbell KP 《Science (New York, N.Y.)》2012,335(6064):93-96
Posttranslational modification of alpha-dystroglycan (α-DG) by the like-acetylglucosaminyltransferase (LARGE) is required for it to function as an extracellular matrix (ECM) receptor. Mutations in the LARGE gene have been identified in congenital muscular dystrophy patients with brain abnormalities. However, the precise function of LARGE remains unclear. Here we found that LARGE could act as a bifunctional glycosyltransferase, with both xylosyltransferase and glucuronyltransferase activities, which produced repeating units of [-3-xylose-α1,3-glucuronic acid-β1-]. This modification allowed α-DG to bind laminin-G domain-containing ECM ligands. 相似文献
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MeCP2, a key contributor to neurological disease, activates and represses transcription 总被引:2,自引:0,他引:2
Chahrour M Jung SY Shaw C Zhou X Wong ST Qin J Zoghbi HY 《Science (New York, N.Y.)》2008,320(5880):1224-1229
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Centrins are highly conserved components of the centrosome, which in the parasitic protozoan T. brucei comprises the basal body and nucleates the flagellum used for locomotion. Here, we found TbCentrin2 in an additional bi-lobed structure near to the Golgi apparatus. One lobe was associated with the old Golgi, and the other became associated with the newly forming Golgi as the cell grew. Depletion of TbCentrin1 inhibited duplication of the basal body, whereas depletion of TbCentrin2 also inhibited duplication of the Golgi. Thus, a Centrin2-containing structure distinct from the basal body appears to mark the site for new Golgi assembly. 相似文献
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Ectodermal Wnt function as a neural crest inducer 总被引:1,自引:0,他引:1
Neural crest cells, which generate peripheral nervous system and facial skeleton, arise at the neural plate/ectodermal border via an inductive interaction between these tissues. Wnts and bone morphogenetic proteins (BMPs) play roles in neural crest induction in amphibians and zebrafish. Here, we show that, in avians, Wnt6 is localized in ectoderm and in vivo inhibition of Wnt signaling perturbs neural crest formation. Furthermore, Wnts induce neural crest from naive neural plates in vitro in a defined medium without added factors, whereas BMPs require additives. Our data suggest that Wnt molecules are necessary and sufficient to induce neural crest cells in avian embryos. 相似文献
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Reversible cryogenic blockade of neural systems in the brain may be accomplished by local cooling. A small cryoprobe is described which may be implanted in the brain of an unrestrained, behaving animal. Cooling may be restricted to the tip of the cryoprobe and the temperature of the tip and the shaft may be regulated and monitored independently by miniature thermocouples and appropriate control and indicator devices. Electrophysiological results are presented which show that the cryogenic blocking effect may be localized to within a few millimeters of the tip of the cryoprobe and that the size of the region blocked is proportional to the tip temperature. The system described has been shown to be effective in both electrophysiological and behavioral studies. 相似文献
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Genes associated with Hirschsprung disease, a failure to form enteric ganglia in the hindgut, were highly up-regulated in gut neural crest stem cells relative to whole-fetus RNA. One of these genes, the glial cell line-derived neurotrophic factor (GDNF) receptor Ret, was necessary for neural crest stem cell migration in the gut. GDNF promoted the migration of neural crest stem cells in culture but did not affect their survival or proliferation. Gene expression profiling, combined with reverse genetics and analyses of stem cell function, suggests that Hirschsprung disease is caused by defects in neural crest stem cell function. 相似文献
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郭宗楼 《浙江大学学报(农业与生命科学版)》2001,27(3):335-338
建立了一个水库水质评价的径向基函数人工神经网络(RBF-ANN)模型,应用一种简便、快速的最小二乘算法训练RBF-ANN.在水库水质评价的应用结果表明,RBF-ANN模型及其算法是合理、有效和通用的. 相似文献
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The cytokine tumor necrosis factor (TNF) is the primary trigger of inflammation. Like many extracellular signaling proteins, TNF is synthesized as a transmembrane protein; the active signal is its ectodomain, which is shed from cells after cleavage by an ADAM family metalloprotease, ADAM17 (TNFα-converting enzyme, TACE). We report that iRhom2 (RHBDF2), a proteolytically inactive member of the rhomboid family, is required for TNF release in mice. iRhom2 binds TACE and promotes its exit from the endoplasmic reticulum. The failure of TACE to exit the endoplasmic reticulum in the absence of iRhom2 prevents the furin-mediated maturation and trafficking of TACE to the cell surface, the site of TNF cleavage. Given the role of TNF in autoimmune and inflammatory diseases, iRhom2 may represent an attractive therapeutic target. 相似文献
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冯芙叶 《西北农林科技大学学报(自然科学版)》2001,29(3):115-116
给出了凸函数极小值点集的几何特征,它是Rn中的一个单连通子集。用神经网络求解优化问题,必须考察的问题是网络的极限点集结构;对梯度神经网络的极限点集进行详细分析,主要结果是对凸函数来说网络的极限点集就是该函数的极小值点集,而这恰是梯度网络求解凸函数总体极值时,网络能够全局稳定收敛的条件。 相似文献
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Soares LM Zanier K Mackereth C Sattler M Valcárcel J 《Science (New York, N.Y.)》2006,312(5782):1961-1965
Discrimination between splice sites and similar, nonsplice sequences is essential for correct intron removal and messenger RNA formation in eukaryotes. The 65- and 35-kD subunits of the splicing factor U2AF, U2AF65 and U2AF35, recognize, respectively, the pyrimidine-rich tract and the conserved terminal AG present at metazoan 3' splice sites. We report that DEK, a chromatin- and RNA-associated protein mutated or overexpressed in certain cancers, enforces 3' splice site discrimination by U2AF. DEK phosphorylated at serines 19 and 32 associates with U2AF35, facilitates the U2AF35-AG interaction and prevents binding of U2AF65 to pyrimidine tracts not followed by AG. DEK and its phosphorylation are required for intron removal, but not for splicing complex assembly, which indicates that proofreading of early 3' splice site recognition influences catalytic activation of the spliceosome. 相似文献
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Gibbons A 《Science (New York, N.Y.)》1990,250(4982):750
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基于思维进化算法径向基函数神经网络的土壤有机质空间异质性研究 总被引:1,自引:0,他引:1
提出一种基于思维进化算法径向基函数神经网络的土壤有机质空间异质性研究方法(MECRBF)。以江西省万年县为案例区,在全县范围内采集耕地表层(0~20 cm)土壤样品954个,分别采用该方法和以邻近信息和地理坐标为输入的径向基函数神经网络方法(RBF-Near),以及普通克里格法来模拟土壤有机质空间分布。以验证样本实测值和预测值的决定系数与逼近误差作为评判标准,对比各方法在县域尺度上土壤有机质空间变异和空间插值方面的效果。对763个采样点进行建模、191个验证样点进行独立验证的预测结果表明,在验证点预测中,MECRBF的均方根误差、平均绝对误差、平均相对误差较RBF-Near分别降低了0.50 g·kg-1、0.39 g·kg-1、1.40百分点,差异显著(P<0.05),较普通克里格法分别降低2.59 g·kg-1、1.89 g·kg-1、7.76百分点,差异显著(P<0.05)。从模拟效果来看,MECRBF的决定系数最高,逼近误差最小;从空间分布模拟图来看,MECRBF能更好地表达土壤有机质空间异质性。提出的MECRBF可为县域尺度下土壤性质空间异质性研究提供方法参考。 相似文献
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Nodulation signaling in legumes requires NSP2, a member of the GRAS family of transcriptional regulators 总被引:1,自引:0,他引:1
Kaló P Gleason C Edwards A Marsh J Mitra RM Hirsch S Jakab J Sims S Long SR Rogers J Kiss GB Downie JA Oldroyd GE 《Science (New York, N.Y.)》2005,308(5729):1786-1789
Rhizobial bacteria enter a symbiotic interaction with legumes, activating diverse responses in roots through the lipochito oligosaccharide signaling molecule Nod factor. Here, we show that NSP2 from Medicago truncatula encodes a GRAS protein essential for Nod-factor signaling. NSP2 functions downstream of Nod-factor-induced calcium spiking and a calcium/calmodulin-dependent protein kinase. We show that NSP2-GFP expressed from a constitutive promoter is localized to the endoplasmic reticulum/nuclear envelope and relocalizes to the nucleus after Nod-factor elicitation. This work provides evidence that a GRAS protein transduces calcium signals in plants and provides a possible regulator of Nod-factor-inducible gene expression. 相似文献
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