Transposon-dependent mutant phenotypes at the Notch locus of Drosophila

Many mutations at complex genetic loci in the fruitfly Drosophila melanogaster are associated with insertions of transposable elements. At the Notch locus, members of one class of insertion-associated mutations, termed glossy-like, produce a recessive viable, smooth-eye phenotype with mottled pigmentation. Members of a second class, facet, produce a recessive viable, rough-eye phenotype with homogeneous pigmentation. Both classes of mutations fail to complement Notch lethal mutations, so they behave as Notch alleles. Here we report that each glossy-like mutation is associated with an insertion of the same transposable element (flea). Each flea insertion occurs in the same orientation, but at different locations within intervening sequences of the Notch locus. In contrast, each facet mutation is associated with insertion of a unique, non-flea, transposable element. Insertions producing a facet phenotype and insertions causing a glossy-like phenotype can break Notch intervening sequences at precisely the same location. This suggests that the type of insertion element rather than its position within an affected gene is the primary determinant of the phenotype observed.     

Reduced sleep in Drosophila Shaker mutants

Most of us sleep 7-8 h per night, and if we are deprived of sleep our performance suffers greatly; however, a few do well with just 3-4 h of sleep-a trait that seems to run in families. Determining which genes underlie this phenotype could shed light on the mechanisms and functions of sleep. To do so, we performed mutagenesis in Drosophila melanogaster, because flies also sleep for many hours and, when sleep deprived, show sleep rebound and performance impairments. By screening 9,000 mutant lines, we found minisleep (mns), a line that sleeps for one-third of the wild-type amount. We show that mns flies perform normally in a number of tasks, have preserved sleep homeostasis, but are not impaired by sleep deprivation. We then show that mns flies carry a point mutation in a conserved domain of the Shaker gene. Moreover, after crossing out genetic modifiers accumulated over many generations, other Shaker alleles also become short sleepers and fail to complement the mns phenotype. Finally, we show that short-sleeping Shaker flies have a reduced lifespan. Shaker, which encodes a voltage-dependent potassium channel controlling membrane repolarization and transmitter release, may thus regulate sleep need or efficiency.     

Frizzled regulation of Notch signalling polarizes cell fate in the Drosophila eye

The Drosophila eye, a paradigm for epithelial organization, is highly polarized with mirror-image symmetry about the equator. The R3 and R4 photoreceptors in each ommatidium are vital in this polarity; they adopt asymmetrical positions in adult ommatidia and are the site of action for several essential genes. Two such genes are frizzled (fz) and dishevelled (dsh), the products of which are components of a signalling pathway required in R3, and which are thought to be activated by a diffusible signal. Here we show that the transmembrane receptor Notch is required downstream of dsh in R3/R4 for them to adopt distinct fates. By using an enhancer for the Notch target gene Enhancer of split mdelta, we show that Notch becomes activated specifically in R4. We propose that Fz/Dsh promotes activity of the Notch ligand Delta and inhibits Notch receptor activity in R3, creating a difference in Notch signalling capacity between R3 and R4. Subsequent feedback in the Notch pathway ensures that this difference becomes amplified. This interplay between Fz/Dsh and Notch indicates that polarity is established through local comparisons between two cells and explains how a signal from one position (for example, the equator in the eye) could be interpreted by all ommatidia in the field.     

Mitochondrial dysfunction in Drosophila PINK1 mutants is complemented by parkin

Autosomal recessive juvenile parkinsonism (AR-JP) is an early-onset form of Parkinson's disease characterized by motor disturbances and dopaminergic neurodegeneration. To address its underlying molecular pathogenesis, we generated and characterized loss-of-function mutants of Drosophila PTEN-induced putative kinase 1 (PINK1), a novel AR-JP-linked gene. Here, we show that PINK1 mutants exhibit indirect flight muscle and dopaminergic neuronal degeneration accompanied by locomotive defects. Furthermore, transmission electron microscopy analysis and a rescue experiment with Drosophila Bcl-2 demonstrated that mitochondrial dysfunction accounts for the degenerative changes in all phenotypes of PINK1 mutants. Notably, we also found that PINK1 mutants share marked phenotypic similarities with parkin mutants. Transgenic expression of Parkin markedly ameliorated all PINK1 loss-of-function phenotypes, but not vice versa, suggesting that Parkin functions downstream of PINK1. Taken together, our genetic evidence clearly establishes that Parkin and PINK1 act in a common pathway in maintaining mitochondrial integrity and function in both muscles and dopaminergic neurons.     

Defective processing and presentation of exogenous antigens in mutants with normal HLA class II genes

Presentation of an exogenous protein antigen to helper (CD4+)T-lymphocytes by antigen presenting cells (APC) generally requires that the APCs degrade the native protein antigen into an immunogenic peptide, a process termed 'antigen processing', and that this peptide bind to a major histocompatibility complex (MHC) class II molecule. The complex of peptide and MHC molecule on the APC surface provides the stimulatory ligand for the alpha beta T cell receptor. The intracellular pathways and molecular mechanisms involved in the generation of the peptide-MHC complex are not well understood. Here, we describe several mutant APCs which are altered in their ability to present native exogenous protein antigens but effectively present immunogenic peptides derived from these proteins. The lesions in these mutants are not in the class II structural genes, but they affect the conformation of mature class II dimers.     

Detection of virus-specific sequences in Drosophila melanogaster mutants induced by injection of RSV DNA into early embryos

The injection of purified Rous sarcoma virus (RSV) (Prague strain) into Drosophila melanogaster (Oregon R line) eggs changes the fly phenotype in certain cases, and RSV-specific sequences can be identified in the Drosophila genome (ref. 1 and preceding paper). Here we have used Southern blotting to analyse in greater detail the proviral DNA present in several mutant lines of D. melanogaster produced by microinjection of intact RSV or plasmid DNA containing the viral insert. In certain populations of flies, RSV provirus was found to be incorporated into cellular DNA, and in one mutant family the unintegrated form of plasmid DNA was identified. Generally, the presence of injected genetic material in fly cells correlated with morphological changes in Drosophila.     

Presenilin is required for proper morphology and function of neurons in C. elegans

Mutations in the human presenilin genes cause the most frequent and aggressive forms of familial Alzheimer's disease (FAD). Here we show that in addition to its role in cell fate decisions in non-neuronal tissues, presenilin activity is required in terminally differentiated neurons in vivo. Mutations in the Caenorhabditis elegans presenilin genes sel-12 and hop-1 result in a defect in the temperature memory of the animals. This defect is caused by the loss of presenilin function in two cholinergic interneurons that display neurite morphology defects in presenilin mutants. The morphology and function of the affected neurons in sel-12 mutant animals can be restored by expressing sel-12 only in these cells. The wild-type human presenilin PS1, but not the FAD mutant PS1 A246E, can also rescue these morphological defects. As lin-12 mutant animals display similar morphological and functional defects to presenilin mutants, we suggest that presenilins mediate their activity in postmitotic neurons by facilitating Notch signalling. These data indicate cell-autonomous and evolutionarily conserved control of neural morphology and function by presenilins.     

Wolbachia在Drosophila auraria复合种和Drosophila simulans中的感染

用 Ｐ Ｃ Ｒ 方法检测了多种果蝇中共生菌 Ｗ ｏｌｂａｃｈｉａ 的感染,发现 Ｄｒｏｓｏｐｈｉｌａ ａｕｒａｒｉａ 复合种以及采集于北京地区的 Ｄｒｏｓｏｐｈｉｌａ ｓｉｍ ｕｌａｎｓ为 Ｗｏｌｂａｃｈｉａ 所感染, Ｒ Ｆ Ｌ Ｐ分析证实为单一感染．克隆了编码 Ｗ ｏｌｂａｃｈｉａ 外膜蛋白质的 ｗ ｓｐ 基因并进行了序列测定．同时比较了 Ｄｒｏｓｏｐｈｉｌａ ａｕｒａｒｉａ 复合种内 ４ 个种和采集于北京及美国加州的 Ｄｒｏｓｏｐｈｉｌａ ｓｉｍ ｕｌａｎｓ 的线粒体的细胞色素氧化酶 ２ 亚基基因的部分序列． 进而讨论了 Ｗｏｌｂａｃｈｉａ 对 Ｄｒｏｓｏｐｈｉｌａ ａｕｒａｒｉａ 复合种成员之间进化关系的影响．     

PDGF-BB和 Notch1在卵巢癌中的表达

探讨PDGF-BB及Notch 1在卵巢癌发生发展中的作用及与临床病理特征的关系,采用免疫组化SP法检测PDGF-BB及Notch1在卵巢癌组织中的表达情况。在60例卵巢癌组织中,PDGF-BB阳性染色主要位于细胞浆中。60%(36/60)高表达,40%(24/60)低表达。Notch1阳性染色主要位于细胞膜中,细胞核、细胞浆亦有表达。63%(38/60)高表达,37%(22/60)低表达。在10例正常卵巢组织中,PDGF-BB部分染色显示高表达10%(1/10),其余均为低表达。Notch1部分染色显示高表达20%(2/10),其余均为低表达。说明在卵巢癌组织中,PDGF-BB的阳性表达率明显高于正常卵巢组织,提示PDGF-BB的表达与卵巢癌的发生有明确的关系;同时PDGF-BB表达水平与卵巢癌的分期、病理分级及淋巴结转移相关。Notch1的阳性表达率明显高于正常卵巢组织,提示Notch1的表达与卵巢癌的发生有明确的关系;同时Notch1表达水平与卵巢癌的分期、病理分级及淋巴结转移相关。相关性分析发现卵巢癌中PDGF-BB表达与Notch1的表达呈正相关(P0.05)。     

爆炸载荷作用下刻槽炮孔动态裂纹扩展规律

基于准静态爆生气体膨胀和岩石断裂力学理论，建立了不耦合装药刻槽爆破时的脆性断裂爆破模型。对刻槽炮孔内爆生气体压力、临界压力和应力强度因子进行了分析计算，从而得出了刻槽炮孔裂缝在扩展过程中，包括启裂、止裂条件、启裂方向、扩展长度和裂缝扩展速度等的变化规律。此外，论文还对刻槽爆破时的动态效应进行了初步探讨，根据分析结果在大理石切割爆破中进行了刻槽试验，并和普通光面爆破效果进行了比较。