果蝇长寿基因methuselah的研究进展

果蝇Drosophila 3号染色体上methuselah （mth）基因发生突变后, 成年果蝇的平均寿命会延长约35%, 并且对一系列外界胁迫因素如饥饿、 高温、 百草枯（可产生强氧化性自由基）的耐受性会显著增强。研究表明mth编码的Mth蛋白属于B家族G蛋白偶联受体（G protein-coupled receptor, GPCR）, 其内源性配体是sun基因编码的小分子肽Stunted。现已发现敲除sun基因或者过表达Mth受体的肽类拮抗剂均能延长果蝇的寿命。Mth受体是目前发现的首个与动物衰老调控相关的GPCR, 该受体除了具有GPCR典型的7次跨膜结构外, 还具有其独特的胞外结构域, 该胞外结构域能够与多种配体结合。Mth受体的生理功能主要体现为： 维持生物体内环境稳态和新陈代谢的平衡, 参与调控果蝇的寿命、 应激反应、 雄性种系干细胞数量和感知运动能力等。目前对Mth受体的研究尚处于起步阶段, 其工作机理的解析对于我们揭示GPCR如何参与寿命的调节具有重要意义, 为我们开发延长人类寿命的新药提供了可能。鉴于此, 本文主要对果蝇Mth受体的结构功能、 配体及其寿命调控信号转导通路等方面做了总结, 并对Mth受体寿命调控信号通路的实用研究价值做了一些展望。     

共生表皮葡萄球菌促进果蝇胚后发育

【背景】动物体定殖有多种共生微生物,这些共生微生物严重影响着宿主生理和病理,日益成为研究热点之一。【目的】分离与鉴定黑腹果蝇共生菌,探究表皮葡萄球菌对黑腹果蝇的发育影响和潜在作用机制。【方法】用CEM培养基(Carotenoid expression medium)从果蝇肠道内分离细菌,通过16SrRNA基因序列比对鉴定菌株;以发育时间和幼虫表面积检测果蝇的发育时期和生长速率;利用实时定量PCR检测果蝇促前胸腺激素与胰岛素通路的激活。【结果】从果蝇体内分离到的菌株为表皮葡萄球菌,该菌可以有效定殖于果蝇的肠道。表皮葡萄球菌通过提高果蝇生长速率而显著促进其发育。在分子水平上,表皮葡萄球菌激活PTTH和胰岛素信号以刺激宿主的生长发育。【结论】表皮葡萄球菌是果蝇的一种共生菌,可以通过调控PTTH和胰岛素信号而刺激果蝇生长发育。     

果蝇心脏发育研究三十年进展

果蝇(Drosophila melanogaster)作为最早用于研究心脏发育基因调控的模式生物,已经走过三十年的历程。果蝇心脏发育过程经历了胚胎期、幼虫期和成虫期三大阶段。在胚胎早期, Tinman、Dorsocross和Pannier等基因是关键的调控因子。Tinman参与最早的心脏前体细胞分化和心脏细胞形成,而Dorsocross和Pannier则影响心脏前体细胞的定向分化和心脏管腔的形成。进入胚胎晚期和幼虫期,果蝇的心管经历进一步的发展和重塑,该过程主要受到转录因子Hand、Mef2以及Hox基因家族的调控。在成虫期, Hox基因家族和Tinman依旧发挥重要作用。虽然果蝇心脏与脊椎动物成熟心脏存在形态上的差异,但两者心脏的早期发育过程以及调控基因和信号通路都有保守性。本文综述了果蝇心脏发育基因调控研究的三十年进展以及利用果蝇模型研究人类心脏相关疾病的潜在希望。     

胰岛素信号转导、昆虫发育与老化

胰岛素及其信号转导的探讨为当代生物学一大热点,研究显示:从线虫到果蝇、小鼠及其人类其胰岛素信号转导路径十分类似。昆虫胰岛素的研究开始于家蚕,在20世纪80年代,日本学者在分离家蚕促前胸腺激素(prothoracictropic hormone,简称PTTH)时,发现所纯化的为一称为家蚕素的神经激素,该激素之氨基酸排列顺序与高等动物体内的胰岛素部分相似,但是家蚕素的生理功能至今仍不是很清楚。而果蝇的分子遗传学研究则显示,胰岛素及其信号转导调控果蝇的生长、发育、寿命等许许多多的生理现象。专一性地改变果蝇前胸腺之胰岛素信号转导,会严重影响幼虫的蜕皮与变态。而作者利用家蚕所进行的研究更显示,将牛的胰岛素注射于家蚕幼虫体内可显着提高其蜕皮激素的分泌,离体培养前胸腺时加入牛胰岛素也可直接增加其激素的分泌,牛胰岛素可直接活化家蚕前胸腺细胞之胰岛素受体及信号分子Akt的磷酸化。另外,从线虫、果蝇到小鼠胰岛素及其信号转导突变体的研究结果显示了胰岛素信号转导调控寿命的重要性。利用猴子及人所进行的研究结果显示,低卡路里摄取之所以会延长寿命是因为卡路里的摄取与胰岛素信号转导的变化有关。因此,不同物种利用相同的胰岛素信号转导通路调控发育及老化机制,该发现大大鼓舞了科学家们利用低等的生物来研究复杂的生命现象。     

甲醛对果蝇发育和繁殖的影响

甲醛已被广泛用于人们的日常生活中,成为室内环境的主要污染源.为探讨甲醛对动物不同发育阶段的毒性,本文以模式生物果蝇Drosophila melanogaster为对象,研究了饲料中添加不同浓度甲醛对果蝇生长发育的影响.结果显示,当对照组发育至3龄幼虫（孵化后3d）时,与未添加甲醛的对照组相比,饲料中添加0.25％或0....     

灵活操控果蝇翅芽中wingless基因表达水平的策略

【目的】灵活操控靶基因的表达水平对于研究基因的功能十分重要。Gal4/UAS系统已被广泛应用于调控基因表达,可研究果蝇Drosophila等模式生物复杂的生物学问题。受采用载体的特性及插入位点的影响,Gal4或UAS转基因品系在构建好之后,其调控靶基因的能力基本是确定的。本研究旨在在现有Gal4/UAS系统的基础上,开发一种新的策略,实现在果蝇翅芽中灵活操控wingless(wg)基因的表达水平。【方法】用遗传学手段将黑腹果蝇Drosophila melanogaster品系的UAS-wg和UAS-wg-RNAi转基因重组到同一黑腹果蝇品系中。将该重组黑腹果蝇品系与dpp-Gal4黑腹果蝇品系杂交,同时驱动UAS-wg和UAS-wg-RNAi在果蝇幼虫翅芽中共表达。杂交子代幼虫分别放置在不同的温度(18, 25和30℃)下培养。将幼虫翅芽解剖并进行免疫组化染色,测量染色的荧光强度,分析翅芽中wg的表达水平。【结果】在低温(18℃)下,UAS-wg在基因表达调控中起主要作用,wg表现为超表达,但其超表达的效率可被UAS-wg-RNAi有效地削弱。相反,在高温(30℃)下,UAS-wg-RNAi起主导作用,wg的表达受到抑制。并且通过转换温度,可实现wg在翅芽发育的不同阶段在超表达和抑制之间相互转化,从而灵活地操控wg基因在翅芽中的表达水平。【结论】该方法可以灵活操控果蝇翅芽中wg基因的表达水平,对于调控转基因的表达有重要的意义。     

猪背最长肌中胰岛素样生长因子(IGFs)系统基因的发育表达模式

采用荧光定量PCR技术检测了长白猪和梅山猪的背最长肌组织中胰岛素样生长因子1和2(IGF-1和-2)、胰岛素样生长因子1受体和2受体(IGF-1R和-2R)、胰岛素样生长因子结合蛋白3和5(IGFBP-3和-5)基因mRNA丰度在初生(0月龄)、1、2、3、4和5月龄间的表达变化并分析品种间和不同月龄间基因表达的差异及其对肌肉生长发育的影响。结果表明: 两猪种出生后IGF-1 mRNA表达量均表现为逐渐上调, 而IGF-2则恰好相反, 表现为逐渐下调。这与IGF-2主要在胚胎期发挥作用, 而IGF-1则主要在动物个体出生后才发挥促进细胞增殖和个体发育功能的特点相符。IGFRs mRNA与IGFs mRNA 表达的发育性变化模式并不相似, 提示背最长肌组织中IGFRs mRNA 的表达可能没有受到组织局部产生的IGFs调节。长白猪的IGF-1R、IGF-2R 和IGFBP-3 mRNA表达量均在2月龄时达到最高峰, 提示2月龄可能是长白猪IGFs系统发挥作用最为明显的生长发育阶段。以上结果初步揭示猪生长发育过程中胰岛素样生长因子系统基因表达的发育性变化模式和品种差异, 为深入研究胰岛素样生长因子系统基因的相互调控机制提供了基础数据。     

昆虫糖脂代谢研究进展

肥胖症和糖尿病的日趋流行已经成为世界范围内的公共健康问题,其病因主要在于体内血糖/血脂含量升高引起的能量代谢紊乱。大量的证据表明,昆虫可以作为研究人类代谢疾病的理想模型,它不仅能合成与哺乳动物同源的糖脂代谢相关激素(如胰岛素样肽和脂动激素),而且还具有进化保守的代谢信号通路(如雷帕霉素靶蛋白信号通路)及相关器官与组织(如中肠和脂肪体)。本文主要介绍了昆虫糖脂代谢的过程与调控机制,重点涉及脂肪体和绛色细胞的生理功能、胰岛素样肽/脂动激素对血糖的拮抗调节、参与营养物质代谢的胰岛素-胰岛素样生长因子信号通路以及与类固醇激素合成相关的胆固醇代谢等内容,并结合最新研究成果对黑腹果蝇Drosophila melanogaster糖脂代谢相关基因及其功能进行了总结,以期为昆虫生理学和人类代谢疾病研究提供参考。     

类肠膜魏斯氏菌通过调节蜕皮激素和胰岛素通路促进黑腹果蝇生长发育（英文）

【目的】本研究旨在揭示果蝇乳酸菌类肠膜魏斯氏菌Weisellas paramesenteroides对黑腹果蝇Drosophila melanogaster生长发育的影响。【方法】利用选择性培养基分离黑腹果蝇成虫肠道乳酸菌,通过16S rRNA基因序列比对鉴定菌株。通过统计从卵至蛹化和羽化的时间检测果蝇发育历期,并以幼虫体表面积为指标检测果蝇生长速率。利用qPCR检测产卵后不同时间生长激素信号通路基因(dib,E74B和PTTH)及胰岛素信号通路基因(DILP2,DILP3和InR)的表达。通过葡萄糖氧化酶法检测3龄幼虫血淋巴中的葡萄糖水平。【结果】从黑腹果蝇成虫肠道内分离到类肠膜魏斯氏菌,并可以在果蝇肠道内有效定殖。类肠膜魏斯氏菌通过提高果蝇生长速率缩短果蝇卵至蛹化和羽化的时间。qPCR结果显示,类肠膜魏斯氏菌增加了dib,E74B和PTTH的表达量,同时增加了DILP2和DILP3的表达量,降低了InR表达量和幼虫血淋巴中的葡萄糖水平。【结论】类肠膜魏斯氏菌是黑腹果蝇的一种共生菌,通过激活蜕皮激素和胰岛素信号通路,促进生长发育。     

蜕皮激素和IIS-TORC1信号的分子互作

蜕皮激素信号主导调控昆虫的蜕皮和变态,决定昆虫的发育时间;IIS-TORC1信号整合生长因子、激素、营养和能量信号,决定昆虫的生长速率。蜕皮激素和IIS-TORC1信号之间发生3种分子互作:(1)IIS-TORC1信号促进前胸腺和卵巢合成蜕皮激素前体。(2)在蜕皮和变态期间,蜕皮激素抑制脂肪体细胞内IIS-TORC1信号、Myc的转录、细胞生长及其内分泌功能,导致脑神经分泌细胞分泌胰岛素样肽的功能减弱,从而降低昆虫全身性的IIS-TORC1信号。(3)在幼虫摄食期间,胰岛素信号抑制FOXO的转录活性,降低了蜕皮激素受体EcR的转录共激活因子DOR编码基因的转录水平,从而阻碍了蜕皮激素信号传导。蜕皮激素信号和IIS-TORC1信号协同调控发育时间和生长速率共同决定昆虫的个体大小。     

Nitric Oxide Synthase Regulates Growth Coordination During Drosophila melanogaster Imaginal Disc Regeneration

Mechanisms that coordinate growth during development are essential for producing animals with proper organ proportion. Here we describe a pathway through which tissues communicate to coordinate growth. During Drosophila melanogaster larval development, damage to imaginal discs activates a regeneration checkpoint through expression of Dilp8. This both produces a delay in developmental timing and slows the growth of undamaged tissues, coordinating regeneration of the damaged tissue with developmental progression and overall growth. Here we demonstrate that Dilp8-dependent growth coordination between regenerating and undamaged tissues, but not developmental delay, requires the activity of nitric oxide synthase (NOS) in the prothoracic gland. NOS limits the growth of undamaged tissues by reducing ecdysone biosynthesis, a requirement for imaginal disc growth during both the regenerative checkpoint and normal development. Therefore, NOS activity in the prothoracic gland coordinates tissue growth through regulation of endocrine signals.     

High sugar-induced insulin resistance in Drosophila relies on the lipocalin Neural Lazarillo

In multicellular organisms, insulin/IGF signaling (IIS) plays a central role in matching energy needs with uptake and storage, participating in functions as diverse as metabolic homeostasis, growth, reproduction and ageing. In mammals, this pleiotropy of action relies in part on a dichotomy of action of insulin, IGF-I and their respective membrane-bound receptors. In organisms with simpler IIS, this functional separation is questionable. In Drosophila IIS consists of several insulin-like peptides called Dilps, activating a unique membrane receptor and its downstream signaling cascade. During larval development, IIS is involved in metabolic homeostasis and growth. We have used feeding conditions (high sugar diet, HSD) that induce an important change in metabolic homeostasis to monitor possible effects on growth. Unexpectedly we observed that HSD-fed animals exhibited severe growth inhibition as a consequence of peripheral Dilp resistance. Dilp-resistant animals present several metabolic disorders similar to those observed in type II diabetes (T2D) patients. By exploring the molecular mechanisms involved in Drosophila Dilp resistance, we found a major role for the lipocalin Neural Lazarillo (NLaz), a target of JNK signaling. NLaz expression is strongly increased upon HSD and animals heterozygous for an NLaz null mutation are fully protected from HSD-induced Dilp resistance. NLaz is a secreted protein homologous to the Retinol-Binding Protein 4 involved in the onset of T2D in human and mice. These results indicate that insulin resistance shares common molecular mechanisms in flies and human and that Drosophila could emerge as a powerful genetic system to study some aspects of this complex syndrome.     

Lgr5 Marks Post-Mitotic,Lineage Restricted Cerebellar Granule Neurons during Postnatal Development

Wnt signaling regulates self-renewal and fate commitment of stem and progenitor cells in development and homeostasis. Leucine-rich repeat-containing G-protein coupled receptor 5 (Lgr5) is a co-receptor for Wnt signaling that marks highly proliferative stem and progenitor cells in many epithelial tissue types. Wnt signaling instructs neural developmental and homeostatic processes; however, Lgr5 expression in the developing and adult brain has not been characterized. Here we report that Lgr5 is expressed in the postnatal cerebellum during the maturation and synaptogenesis of cerebellar granule neurons (CGNs), processes controlled by Wnt signaling. Using a transgenic reporter mouse for in vivo Lgr5 expression analysis and lineage tracing, we reveal that Lgr5 specifically identified CGNs and was restricted temporally to the CGN maturation phase within the internal granule layer, but absent in the adult brain. Cells marked by Lgr5 were lineage restricted, post-mitotic and long-lived. The ligand for Lgr5, R-spondin, was secreted in a paracrine fashion that evolved during the maturation of CGNs, which coincided with the Lgr5 expression pattern. Our findings provide potential new insight into the critical regulation of Wnt signaling in the developing cerebellum and support a novel role for Lgr5 in the regulation of post-mitotic cells.     

Drosophila Adiponectin Receptor in Insulin Producing Cells Regulates Glucose and Lipid Metabolism by Controlling Insulin Secretion

Adipokines secreted from adipose tissue are key regulators of metabolism in animals. Adiponectin, one of the adipokines, modulates pancreatic beta cell function to maintain energy homeostasis. Recently, significant conservation between Drosophila melanogaster and mammalian metabolism has been discovered. Drosophila insulin like peptides (Dilps) regulate energy metabolism similarly to mammalian insulin. However, in Drosophila, the regulatory mechanism of insulin producing cells (IPCs) by adipokine signaling is largely unknown. Here, we describe the discovery of the Drosophila adiponectin receptor and its function in IPCs. Drosophila adiponectin receptor (dAdipoR) has high homology with the human adiponectin receptor 1. The dAdipoR antibody staining revealed that dAdipoR was expressed in IPCs of larval and adult brains. IPC- specific dAdipoR inhibition (Dilp2>dAdipoR-Ri) showed the increased sugar level in the hemolymph and the elevated triglyceride level in whole body. Dilps mRNA levels in the Dilp2>dAdipoR-Ri flies were similar with those of controls. However, in the Dilp2>dAdipoR-Ri flies, Dilp2 protein was accumulated in IPCs, the level of circulating Dilp2 was decreased, and insulin signaling was reduced in the fat body. In ex vivo fly brain culture with the human adiponectin, Dilp2 was secreted from IPCs. These results indicate that adiponectin receptor in insulin producing cells regulates insulin secretion and controls glucose and lipid metabolism in Drosophila melanogaster. This study demonstrates a new adipokine signaling in Drosophila and provides insights for the mammalian adiponectin receptor function in pancreatic beta cells, which could be useful for therapeutic application.     

Epithelial cell-turnover ensures robust coordination of tissue growth in Drosophila ribosomal protein mutants

Highly reproducible tissue development is achieved by robust, time-dependent coordination of cell proliferation and cell death. To study the mechanisms underlying robust tissue growth, we analyzed the developmental process of wing imaginal discs in Drosophila Minute mutants, a series of heterozygous mutants for a ribosomal protein gene. Minute animals show significant developmental delay during the larval period but develop into essentially normal flies, suggesting there exists a mechanism ensuring robust tissue growth during abnormally prolonged developmental time. Surprisingly, we found that both cell death and compensatory cell proliferation were dramatically increased in developing wing pouches of Minute animals. Blocking the cell-turnover by inhibiting cell death resulted in morphological defects, indicating the essential role of cell-turnover in Minute wing morphogenesis. Our analyses showed that Minute wing discs elevate Wg expression and JNK-mediated Dilp8 expression that causes developmental delay, both of which are necessary for the induction of cell-turnover. Furthermore, forced increase in Wg expression together with developmental delay caused by ecdysone depletion induced cell-turnover in the wing pouches of non-Minute animals. Our findings suggest a novel paradigm for robust coordination of tissue growth by cell-turnover, which is induced when developmental time axis is distorted.     

Insulin- and Warts-Dependent Regulation of Tracheal Plasticity Modulates Systemic Larval Growth during Hypoxia in Drosophila melanogaster

Adaptation to dynamic environmental cues during organismal development requires coordination of tissue growth with available resources. More specifically, the effects of oxygen availability on body size have been well-documented, but the mechanisms through which hypoxia restricts systemic growth have not been fully elucidated. Here, we characterize the larval growth and metabolic defects in Drosophila that result from hypoxia. Hypoxic conditions reduced fat body opacity and increased lipid droplet accumulation in this tissue, without eliciting lipid aggregation in hepatocyte-like cells called oenocytes. Additionally, hypoxia increased the retention of Dilp2 in the insulin-producing cells of the larval brain, associated with a reduction of insulin signaling in peripheral tissues. Overexpression of the wildtype form of the insulin receptor ubiquitously and in the larval trachea rendered larvae resistant to hypoxia-induced growth restriction. Furthermore, Warts downregulation in the trachea was similar to increased insulin receptor signaling during oxygen deprivation, which both rescued hypoxia-induced growth restriction, inhibition of tracheal molting, and developmental delay. Insulin signaling and loss of Warts function increased tracheal growth and augmented tracheal plasticity under hypoxic conditions, enhancing oxygen delivery during periods of oxygen deprivation. Our findings demonstrate a mechanism that coordinates oxygen availability with systemic growth in which hypoxia-induced reduction of insulin receptor signaling decreases plasticity of the larval trachea that is required for the maintenance of systemic growth during times of limiting oxygen availability.     

Drosophila ALS regulates growth and metabolism through functional interaction with insulin-like peptides

In metazoans, factors of the insulin family control growth, metabolism, longevity, and fertility in response to environmental cues. In Drosophila, a family of seven insulin-like peptides, called Dilps, activate a common insulin receptor. Some Dilp peptides carry both metabolic and growth functions, raising the possibility that various binding partners specify their functions. Here we identify dALS, the fly ortholog of the vertebrate insulin-like growth factor (IGF)-binding protein acid-labile subunit (ALS), as a Dilp partner that forms a circulating trimeric complex with one molecule of Dilp and one molecule of Imp-L2, an IgG-family molecule distantly related to mammalian IGF-binding proteins (IGFBPs). We further show that dALS antagonizes Dilp function to control animal growth as well as carbohydrate and fat metabolism. These results lead us to propose an evolutionary perspective in which ALS function appeared prior to the separation between metabolic and growth effects that are associated with vertebrate insulin and IGFs.