Regulation of C. elegans life-span by insulinlike signaling in the nervous system

An insulinlike signaling pathway controls Caenorhabditis elegans aging, metabolism, and development. Mutations in the daf-2 insulin receptor-like gene or the downstream age-1 phosphoinositide 3-kinase gene extend adult life-span by two- to threefold. To identify tissues where this pathway regulates aging and metabolism, we restored daf-2 pathway signaling to only neurons, muscle, or intestine. Insulinlike signaling in neurons alone was sufficient to specify wild-type life-span, but muscle or intestinal signaling was not. However, restoring daf-2 pathway signaling to muscle rescued metabolic defects, thus decoupling regulation of life-span and metabolism. These findings point to the nervous system as a central regulator of animal longevity.     

Quantitative mass spectrometry identifies insulin signaling targets in C. elegans

DAF-2, an insulin receptor-like protein, regulates metabolism, development, and aging in Caenorhabditis elegans. In a quantitative proteomic study, we identified 86 proteins that were more or less abundant in long-lived daf-2 mutant worms than in wild-type worms. Genetic studies on a subset of these proteins indicated that they act in one or more processes regulated by DAF-2, including entry into the dauer developmental stage and aging. In particular, we discovered a compensatory mechanism activated in response to reduced DAF-2 signaling, which involves the protein phosphatase calcineurin.     

Mutations that increase the life span of C. elegans inhibit tumor growth

Mutations in gld-1 cause lethal germline tumors in the nematode Caenorhabditis elegans. We find that a wide variety of mutations that extend C. elegans' life span confer resistance to these tumors. The long life spans of daf-2/insulin-receptor mutants were not shortened at all by gld-1 mutations; we attribute this finding to decreased cell division and increased DAF-16/p53-dependent apoptosis within the tumors. Mutations that increase life span by restricting food intake or inhibiting respiration did not affect apoptosis but reduced tumor cell division. Unexpectedly, none of these longevity mutations affected mitosis in normal germlines; this finding suggests that cellular changes that lead to longevity preferentially antagonize tumor cell growth.     

A mutant Drosophila insulin receptor homolog that extends life-span and impairs neuroendocrine function

The Drosophila melanogaster gene insulin-like receptor (InR) is homologous to mammalian insulin receptors as well as to Caenorhabditis elegans daf-2, a signal transducer regulating worm dauer formation and adult longevity. We describe a heteroallelic, hypomorphic genotype of mutant InR, which yields dwarf females with up to an 85% extension of adult longevity and dwarf males with reduced late age-specific mortality. Treatment of the long-lived InR dwarfs with a juvenile hormone analog restores life expectancy toward that of wild-type controls. We conclude that juvenile hormone deficiency, which results from InR signal pathway mutation, is sufficient to extend life-span, and that in flies, insulin-like ligands nonautonomously mediate aging through retardation of growth or activation of specific endocrine tissue.     

Autophagy genes are essential for dauer development and life-span extension in C. elegans

Both dauer formation (a stage of developmental arrest) and adult life-span in Caenorhabditis elegans are negatively regulated by insulin-like signaling, but little is known about cellular pathways that mediate these processes. Autophagy, through the sequestration and delivery of cargo to the lysosomes, is the major route for degrading long-lived proteins and cytoplasmic organelles in eukaryotic cells. Using nematodes with a loss-of-function mutation in the insulin-like signaling pathway, we show that bec-1, the C. elegans ortholog of the yeast and mammalian autophagy gene APG6/VPS30/beclin1, is essential for normal dauer morphogenesis and life-span extension. Dauer formation is associated with increased autophagy and also requires C. elegans orthologs of the yeast autophagy genes APG1, APG7, APG8, and AUT10. Thus, autophagy is a cellular pathway essential for dauer development and life-span extension in C. elegans.     

Timing requirements for insulin/IGF-1 signaling in C. elegans

The insulin/IGF-1 (where IGF-1 is insulin-like growth factor-1) signaling pathway influences longevity, reproduction, and diapause in many organisms. Because of the fundamental importance of this system in animal physiology, we asked when during the animal's life it is required to regulate these different processes. We find that in Caenorhabditis elegans, the pathway acts during adulthood, to relatively advanced ages, to influence aging. In contrast, it regulates diapause during development. In addition, the pathway controls longevity and reproduction independently of one another. Together our findings show that life-span regulation can be dissociated temporally from phenotypes that might seem to decrease the quality of life.     

Extended longevity in mice lacking the insulin receptor in adipose tissue

Caloric restriction has been shown to increase longevity in organisms ranging from yeast to mammals. In some organisms, this has been associated with a decreased fat mass and alterations in insulin/insulin-like growth factor 1 (IGF-1) pathways. To further explore these associations with enhanced longevity, we studied mice with a fat-specific insulin receptor knockout (FIRKO). These animals have reduced fat mass and are protected against age-related obesity and its subsequent metabolic abnormalities, although their food intake is normal. Both male and female FIRKO mice were found to have an increase in mean life-span of approximately 134 days (18%), with parallel increases in median and maximum life-spans. Thus, a reduction of fat mass without caloric restriction can be associated with increased longevity in mice, possibly through effects on insulin signaling.     

松乳菇子实体两个发育时期的转录组分析

以松乳菇子实体为研究材料,采用de novo测序对松乳菇子实体进行测序与生物信息学分析,探究松乳菇子实体生长发育过程中幼菇期(LDG-1)和成熟期(LDG-2)基因表达的差异,并探寻影响松乳菇生长发育相关的主要基因和代谢通路。测序结果显示,共获得7.44G(LDG-1)和7.21G(LDG-2)的分析数据(clean reads)。KOG功能注释结果显示,松乳菇在幼菇期(LDG-1)和成熟期(LDG-2)具有全面而复杂的基因功能类别。GO富集结果提示,松乳菇在不同生长阶段(LDG-1和LDG-2)的生物代谢功能存在一定的差异。基因表达水平与聚类分析显示,ATP酶、多功能伴侣蛋白等家族基因为LDG-1和LDG-2主要高表达基因,在能量代谢与参与调控细胞周期中起重要作用。分析差异表达基因发现,相较于LDG-1期,LDG-2期有16 789个差异表达基因,其中7 635个基因上调,9 154个基因下调。差异表达基因KEGG富集通路分析结果显示,氧化磷酸化途径是松乳菇幼菇期生长发育过程中能量代谢的关键途径。进一步分析显示,MAPK信号通路是影响松乳菇子实体发育的关键信号通路,在促进松乳菇子实体进行有性生殖和调控菌丝体的极性生长中起重要作用。     

Extension of life-span by loss of CHICO, a Drosophila insulin receptor substrate protein

The Drosophila melanogaster gene chico encodes an insulin receptor substrate that functions in an insulin/insulin-like growth factor (IGF) signaling pathway. In the nematode Caenorhabditis elegans, insulin/IGF signaling regulates adult longevity. We found that mutation of chico extends fruit fly median life-span by up to 48% in homozygotes and 36% in heterozygotes. Extension of life-span was not a result of impaired oogenesis in chico females, nor was it consistently correlated with increased stress resistance. The dwarf phenotype of chico homozygotes was also unnecessary for extension of life-span. The role of insulin/IGF signaling in regulating animal aging is therefore evolutionarily conserved.     

根癌农杆菌胁迫下多花蔷薇（Rosa multiflora'Inermis 4'）的基因表达分析

  多花蔷薇无刺4号（Rosa multiflora'Inermis 4'）对根癌病有较强抗性。以根癌农杆菌(Agrobacterium tumefaciens)接种多花蔷薇无刺4号为目的材料,刺伤处理为对照,采用抑制差减杂交（suppression subtractive hybridization,SSH）方法,构建了富集多花蔷薇根癌病抗性相关基因的差减cDNA文库。差异筛选差减cDNA文库后,随机选取增强表达的92个克隆进行测序,去除冗余的cDNA和病菌的基因片段,共得到53个单一序列。利用GenBank数据库进行核酸和蛋白质同源性比较,获得的cDNA片段功能涉及：细胞分裂、生长（22个克隆）,逆境防御、信号转导及激素调节（11个克隆）以及初生与次生代谢（10个克隆）。另有10个基因片段功能未知,可能为新的EST。根据测序及比对分析结果,对多花蔷薇无刺4号抗根癌病的分子机理进行了探讨。     

人工劣变处理对玉米种胚差异基因表达的影响

【目的】利用数字基因表达谱技术（digital gene expression tag profiling,DGE）探索人工控制劣变（controlled deterioration treatment,CDT）条件下玉米种胚差异基因的表达变化,为揭示种子劣变的分子机理提供依据。【方法】以玉米杂交种郑单958种子为材料,采用高温（45℃）高湿（相对湿度100%）方法处理72 h,以未处理材料为对照,利用DGE分别进行高通量测序,测序结果与参考基因组和参考基因数据库比对获得表达基因,利用RPKM（Reads Per Kb per Million reads）方法计算基因的表达量,根据FDR（false discovery rate)<0.001和|log2 ratio(T/CK)|≥1的标准筛选差异表达的基因,对获得的差异表达基因（digital expression genes,DEGs）进行GO（gene ontology）和KEGG（kyoto encyclopedia of genes and genomes）数据库功能注释,并对注释结果进行富集分析处理。【结果】对照玉米种胚中检测到32 000多种mRNAs。CDT处理后差异表达基因有4 713个。其中上调表达2 874个,下调表达1 839个。GO富集分析表明,这些基因涉及细胞组分、分子功能和生物学过程方面,其编码的蛋白主要分布在细胞器和细胞膜上,参与能量代谢、信号转导、刺激响应和衰老死亡等过程,具有结合、催化和抗氧化等功能。这些基因中,能被KEGG数据库注释的有2 470个,参与了288条代谢通路,其中有16条通路存在着显著性富集。这些通路中,参与能量代谢的基因共有113个,分别参与糖酵解/糖异生过程（59个）、磷酸戊糖途径（31个）和丙酮酸代谢过程（50个）;其中,调节糖酵解/糖异生过程的烯醇化酶基因、3-磷酸甘油醛脱氢酶基因等、丙酮酸代谢中的丙酮酸激酶基因等和磷酸戊糖途径中的α-L-岩藻糖苷酶基因等上调幅度最大。还发现,调节NADH代谢相关的基因有25个（9个上调,16个下调）;NADPH代谢的有10个（4个上调,6个下调）。这些基因的表达变化能够调节活性氧的产生和积累。【结论】DGE可以作为研究种子劣变和活力丧失的有效手段。CDT能够影响玉米种胚差异基因的表达,进而影响细胞能量代谢相关过程,主要表现在糖酵解途径受到抑制,导致ROS产生和积累,从而加速玉米种胚细胞的衰老及死亡,最终造成种子的劣变和活力丧失。在这个过程中,差异表达基因可能扮演重要角色。     

高低肌内脂肪猪背最长肌关键基因表达差异分析

【目的】筛选出高肌内脂肪(Intramuscular fat,IMF)沉积的关键基因并进行表达验证,为揭示猪肌内脂肪沉积的分子调控机制提供理论依据。【方法】根据NCBI-GEO数据库中高、低肌内脂肪巴克夏群体的转录组数据,利用DESeq2进行差异表达基因筛选(|log₂Fold Change|≥1,FDR<0.05),采用Metascape对差异表达基因进行功能富集分析,通过MCODE筛选及鉴定出高肌内脂沉积的关键基因,并采用实时荧光定量PCR在地方猪(柯乐猪)和外种猪(杜长大猪)上进行关键基因表达量验证。【结果】从高、低肌内脂肪巴克夏群体6个文库中共鉴定出7661个基因,高肌内脂肪群体样本的脂质代谢相关基因总表达量显著高于低肌内脂肪群体样本(P<0.05,下同),其中差异表达基因有133个[110个上调(在高肌内脂肪群体高表达),23个下调(在低肌内脂肪群体高表达)]。上调差异表达基因主要富集于胶原蛋白绑定、细胞外基质组装、脂肪酰辅酶A生物合成过程、固醇代谢过程和脂质代谢调控过程等GO功能条目,以及脂肪乙酰辅酶A生物合成、ChREBP激活代谢基因、脂肪酸代谢等信号通路上;下调基因主要富集于线粒体组装、多细胞生物学过程、辅酶绑定和缺氧反应等GO功能条目,以及基于NFKB的TNFA信号、白细胞介素4和白细胞介素13信号和干扰素信号等信号通路上。通过MCODE分析共筛选获得5个关键基因,分别是SLC25A5、FN1、FASN、ACACA和PRKDC基因;挑选SCD、FASN和ACACA基因进行表达量验证,结果发现这3个基因的相对表达量均表现为柯乐猪高于杜长大猪,其差异达显著或极显著(P<0.01)水平,进一步佐证SCD、FASN和ACACA基因在高肌内脂肪猪群体中高表达。【结论】在巴克夏猪高肌内脂肪群体中高表达的SCD、FASN和ACACA基因,在高肌内脂肪的柯乐猪中也呈显著或极显著高表达,因此这3个关键基因有望作为筛选和培育高肌内脂肪猪品种的分子标记,同时为研究肌内脂肪沉积的分子调控机制提供技术支撑。