Study of tauopathies by comparing <Emphasis Type="Italic">Drosophila</Emphasis> and human <Emphasis Type="Italic">tau</Emphasis> in <Emphasis Type="Italic">Drosophila</Emphasis>

The microtubule-binding protein tau has been investigated for its contribution to various neurodegenerative disorders. However, the findings from transgenic studies, using the same tau transgene, vary widely among different laboratories. Here, we have investigated the potential mechanisms underlying tauopathies by comparing Drosophila (d-tau) and human (h-tau) tau in a Drosophila model. Overexpression of a single copy of either tau isoform in the retina results in a similar rough eye phenotype. However, co-expression of Par-1 with d-tau leads to lethality, whereas co-expression of Par-1 with h-tau has little effect on the rough eye phenotype. We have found analogous results by comparing larval proteomes. Through genetic screening and proteomic analysis, we have identified some important potential modifiers and tau-associated proteins. These results suggest that the two tau genes differ significantly. This comparison between species-specific isoforms may help to clarify whether the homologous tau genes are conserved. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. This study was supported by the National Science Foundation of China (30270341; 30630028), the Multidisciplinary Program (Brain and Mind) of the Chinese Academy of Sciences, the Major State Basic Research Program (“973 program”; G2000077800; G2006CB806600; 2006CB911003), the Precedent Project of Important Intersectional Disciplines in the Knowledge Innovation Engineering of the Chinese Academy of Sciences (KJCX1-09-03).     

Substrate regulation of serotonin and dopamine synthesis in <Emphasis Type="Italic">Drosophila</Emphasis>

In Drosophila melanogaster, serotonin (5-hydroxytryptamine, 5-HT) is required for both very early non-neuronal developmental events, and in the CNS as a neurotransmitter to modulate behavior. 5-HT is synthesized, at least in part, by the actions of Drosophila tryptophan-phenylalanine hydroxylase (DTPH), a dual function enzyme that hydroxylates both phenylalanine and tryptophan. DTPH is expressed in numerous tissues as well as dopaminergic and serotonergic neurons, but it does not necessarily function as both enzymes in these tissues. Deficiencies in DTPH could affect the production of dopamine and serotonin, and thus dopaminergic and serotonergic signaling pathways. In this paper, we show that DTPH exhibits differential hydroxylase activity based solely on substrate. When DTPH uses phenylalanine as a substrate, regulatory control (end product inhibition, decreased PAH activity following phosphorylation, catecholamine inhibition) is observed that is not seen when the enzyme uses tryptophan as a substrate. These studies suggest that regulation of DTPH enzymatic activity occurs, at least in part, through the actions of its substrate.     

<Emphasis Type="Italic">Drosophila</Emphasis><Emphasis Type="Italic">P</Emphasis> transposons of the urochordata <Emphasis Type="Italic">Ciona intestinalis</Emphasis>

P transposons belong to the eukaryotic DNA transposons, which are transposed by a cut and paste mechanism using a P-element-coded transposase. They have been detected in Drosophila, and reside as single copies and stable homologous sequences in many vertebrate species. We present the P elements Pcin1, Pcin2 and Pcin3 from Ciona intestinalis, a species of the most primitive chordates, and compare them with those from Ciona savignyi. They showed typical DNA transposon structures, namely terminal inverted repeats and target site duplications. The coding region of Pcin1 consisted of 13 small exons that could be translated into a P-transposon-homologous protein. C. intestinalis and C. savignyi displayed nearly the same phenotype. However, their P elements were highly divergent and the assumed P transposase from C. intestinalis was more closely related to the transposase from Drosophila melanogaster than to the transposase of C. savignyi. The present study showed that P elements with typical features of transposable DNA elements may be found already at the base of the chordate lineage. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

<Emphasis Type="Italic">Drosophila</Emphasis> by the dozen

A report of the 48th Annual Drosophila Research Conference, Philadelphia, USA, 7-11 March 2007.     

Various <Emphasis Type="Italic">Wolbachia</Emphasis> genotypes differently influence host <Emphasis Type="Italic">Drosophila</Emphasis> dopamine metabolism and survival under heat stress conditions

Background

One of the most widespread prokaryotic symbionts of invertebrates is the intracellular bacteria of Wolbachia genus which can be found in about 50% of insect species. Wolbachia causes both parasitic and mutualistic effects on its host that include manipulating the host reproductive systems in order to increase their transmission through the female germline, and increasing the host fitness. One of the mechanisms, promoting adaptation in biological organisms, is a non-specific neuroendocrine stress reaction. In insects, this reaction includes catecholamines, dopamine, serotonin and octopamine, which act as neurotransmitters, neuromodulators and neurohormones. The level of dopamine metabolism correlates with heat stress resistance in Drosophila adults.

Results

To examine Wolbachia effect on Drosophila survival under heat stress and dopamine metabolism we used five strains carrying the nuclear background of interbred Bi90 strain and cytoplasmic backgrounds with different genotype variants of Wolbachia (produced by 20 backcrosses of Bi90 males with appropriate source of Wolbachia). Non-infected Bi90 strain (treated with tetracycline for 3 generations) was used as a control group. We demonstrated that two of five investigated Wolbachia variants promote changes in Drosophila heat stress resistance and activity of enzymes that produce and degrade dopamine, alkaline phosphatase and dopamine-dependent arylalkylamine N-acetyltransferase. What is especially interesting, wMelCS genotype of Wolbachia increases stress resistance and the intensity of dopamine metabolism, whereas wMelPop strain decreases them. wMel, wMel2 and wMel4 genotypes of Wolbachia do not show any effect on the survival under heat stress or dopamine metabolism. L-DOPA treatment, known to increase the dopamine content in Drosophila, levels the difference in survival under heat stress between all studied groups.

Conclusions

The genotype of symbiont determines the effect that the symbiont has on the stress resistance of the host insect.

     

Revealing the anti-HRP epitope in <Emphasis Type="Italic">Drosophila</Emphasis> and <Emphasis Type="Italic">Caenorhabditis</Emphasis>

Antibodies are very often used as specific cell and/or tissue markers. An example of this is anti-horseradish peroxidase (HRP), an antibody raised against a plant glycoprotein, which was shown some twenty-five years ago to specifically stain neural tissue in an animal, Drosophila melanogaster. This peculiar finding was later expanded to other invertebrate species including Caenorhabditis elegans, which were also shown to bear anti-HRP epitopes. Initial experiments indicated that the epitopes recognised by anti-HRP in invertebrates are of carbohydrate nature. Indeed, more recent experiments have characterised relevant core α1-3-fucosylated N-glycan structures that act as epitopes in various model and parasitic organisms. Moreover, a number of enzymes required for the synthesis of such structures have been identified. Over the years, medically-relevant roles of these structures have become apparent as regards allergenicity and immunoregulation. Although major advances have been made in understanding of the underlying mechanisms and structures related to the anti-HRP epitope, the in vivo role of the relevant epitopes in neural and other tissues is yet to be resolved. Current understanding of the anti-HRP epitopes synthesis and their relevance is discussed and elaborated.

Allozyme polymorphism in <Emphasis Type="Italic">Drosophila</Emphasis>

Every population possesses genetic variations which are achieved through gene mutation, genetic recombination, hybridization, gene duplication etc. These genetic variations provide raw materials for evolutionary forces to create a better surviving species. Genetic polymorphism is reflected at every level in the populations, for example, at phenotypic, chromosomal, protein and DNA levels. Protein or enzyme polymorphisms have been well studied in various organisms including Drosophila and humans. Drosophila has proven to be a good model organism for carrying out polymorphism studies. Among the different species of Drosophila, there is a wide variation in the levels of allozyme polymorphisms and heterozygosities which depends upon species, geographical regions, number and nature of loci in question etc. In Drosophila, the average polymorphic enzyme loci and average heterozygosity ranges from 35 to 70 percent and 10 to 20 percent respectively. The genetic differentiation as observed through allozyme or isozyme variation affords an important parameter in evaluating the phylogenetic relationships between different species of Drosophila and also for discussing the adaptive significance of allozyme polymorphisms. Therefore, this review attempts to compile all studies on allozyme polymorphism in Drosophila that have been undertaken so far.     

<Emphasis Type="Italic">Sex combs reduced</Emphasis> (<Emphasis Type="Italic">Scr</Emphasis>) regulatory region of <Emphasis Type="Italic">Drosophila</Emphasis> revisited

The Hox gene Sex combs reduced (Scr) is responsible for the differentiation of the labial and prothoracic segments in Drosophila. Scr is expressed in several specific tissues throughout embryonic development, following a complex path that must be coordinated by an equally complex regulatory region. Although some cis-regulatory modules (CRMs) have been identified in the Scr regulatory region (~75 kb), there has been no detailed and systematic study of the distinct regulatory elements present within this region. In this study, the Scr regulatory region was revisited with the aim of filling this gap. We focused on the identification of Initiator elements (IEs) that bind segmentation factors, Polycomb response elements (PREs) that are recognized by the Polycomb and Trithorax complexes, as well as insulators and tethering elements. To this end, we summarized all currently available information, mainly obtained from high throughput ChIP data projects. In addition, a bioinformatic analysis based on the evolutionary conservation of regulatory sequences using the software MOTEVO was performed to identify IE and PRE candidates in the Scr region. The results obtained by this combined strategy are largely consistent with the CRMs previously identified in the Scr region and help to: (i) delimit them more accurately, (ii) subdivide two of them into different independent elements, (iii) identify a new CRM, (iv) identify the composition of their binding sites and (v) better define some of their characteristics. These positive results indicate that an approach that integrates functional and bioinformatic data might be useful to characterize other regulatory regions.     

Functional conservation of the human <Emphasis Type="Italic">EXT1</Emphasis> tumor suppressor gene and its <Emphasis Type="Italic">Drosophila</Emphasis> homolog <Emphasis Type="Italic">tout</Emphasis><Emphasis Type="Italic">velu</Emphasis>

Heparan sulfate proteoglycans play a vital role in signaling of various growth factors in both Drosophila and vertebrates. In Drosophila, mutations in the tout velu (ttv) gene, a homolog of the mammalian EXT1 tumor suppressor gene, leads to abrogation of glycosaminoglycan (GAG) biosynthesis. This impairs distribution and signaling activities of various morphogens such as Hedgehog (Hh), Wingless (Wg), and Decapentaplegic (Dpp). Mutations in members of the exostosin (EXT) gene family lead to hereditary multiple exostosis in humans leading to bone outgrowths and tumors. In this study, we provide genetic and biochemical evidence that the human EXT1 (hEXT1) gene is conserved through species and can functionally complement the ttv mutation in Drosophila. The hEXT1 gene was able to rescue a ttv null mutant to adulthood and restore GAG biosynthesis.     

A novel family of mitochondrial proteins is represented by the <Emphasis Type="Italic">Drosophila</Emphasis> genes <Emphasis Type="Italic">slmo</Emphasis>, <Emphasis Type="Italic">preli-like</Emphasis> and <Emphasis Type="Italic">real-time</Emphasis>

Mitochondria play essential roles in development and disease. The characterisation of mitochondrial proteins is therefore of particular importance. The slowmo (slmo) gene of Drosophila melanogaster has been shown to encode a novel type of mitochondrial protein, and is essential in the developing central nervous system. The Slmo protein contains a conserved PRELI/MSF1p domain, found in proteins from a wide variety of eukaryotic organisms. However, the function of the proteins of this family is currently unknown. In this study, the evolutionary relationships between members of the PRELI/MSF1p family are described, and we present the first analysis of two novel Drosophila genes predicted to encode proteins of this type. The first of these, preli-like (prel), is expressed ubiquitously during embryonic development, whilst the second, real-time (retm), is expressed dynamically in the developing gut and central nervous system. retm encodes a member of a novel conserved subclass of larger PRELI/MSF1p domain proteins, which also contain the CRAL-TRIO motif thought to mediate the transport of small hydrophobic ligands. Here we provide evidence that, like Slmo, both the Prel and Retm proteins are localised to the mitochondria, indicating that the function of the PRELI/MSF1p domain is specific to this organelle.Edited by P. Simpson     

<Emphasis Type="Italic">Ty</Emphasis>1<Emphasis Type="Italic">/copia</Emphasis>- and <Emphasis Type="Italic">Ty</Emphasis>3<Emphasis Type="Italic">/gypsy</Emphasis>-like DNA sequences in <Emphasis Type="Italic">Helianthus </Emphasis>species

Two repeated DNA sequences isolated from a partial genomic DNA library of Helianthus annuus, p HaS13 and p HaS211, were shown to represent portions of the int gene of a Ty3 /gypsy retroelement and of the RNase-Hgene of a Ty1 /copia retroelement, respectively. Southern blotting patterns obtained by hybridizing the two probes to BglII- or DraI-digested genomic DNA from different Helianthus species showed p HaS13 and p HaS211 were parts of dispersed repeats at least 8 and 7 kb in length, respectively, that were conserved in all species studied. Comparable hybridization patterns were obtained in all species with p HaS13. By contrast, the patterns obtained by hybridizing p HaS211 clearly differentiated annual species from perennials. The frequencies of p HaS13- and p HaS211-related sequences in different species were 4.3x10(4)-1.3x10(5) copies and 9.9x10(2)-8.1x10(3) copies per picogram of DNA, respectively. The frequency of p HaS13-related sequences varied widely within annual species, while no significant difference was observed among perennial species. Conversely, the frequency variation of p HaS211-related sequences was as large within annual species as within perennials. Sequences of both families were found to be dispersed along the length of all chromosomes in all species studied. However, Ty3 /gypsy-like sequences were localized preferentially at the centromeric regions, whereas Ty1/ copia-like sequences were less represented or absent around the centromeres and plentiful at the chromosome ends. These findings suggest that the two sequence families played a role in Helianthusgenome evolution and species divergence, evolved independently in the same genomic backgrounds and in annual or perennial species, and acquired different possible functions in the host genomes.     

Role of arylalkylamine <Emphasis Type="Italic">N</Emphasis>-acetyltransferase in regulation of biogenic amines levels by gonadotropins in <Emphasis Type="Italic">Drosophila</Emphasis>

The effect of 20-hydroxyecdysone (20E) and the juvenile hormone (JH) on the activity of the arylalkylamine N-acetyltransferase (AANAT) was studied in young females of wild-type D. virilis and D. melanogaster. 20E feeding of the flies led to a decrease in AANAT activity in both species when dopamine (DA) was used as substrate, but did not affect the enzyme activity when octopamine (OA) was used as substrate. JH application increased AANAT activity with DA as substrate in both species, but did not change it with OA as substrate. AANAT activity was also measured in young females of a JH-deficient strain of D. melanogaster, apterous ^56f . A decrease in the enzyme activity was observed in the mutant females as compared to wild-type. Mechanisms of regulation of DA level by gonadotropins in Drosophila are discussed.     

<Emphasis Type="Italic">Rab11</Emphasis> is required for myoblast fusion in <Emphasis Type="Italic">Drosophila</Emphasis>

Rab11, an evolutionarily conserved, ubiquitously expressed subfamily of small monomeric Rab GTPases, has been implicated in regulating vesicular trafficking through the recycling of endosomal compartment. In order to gain an insight into the role of this gene in myogenesis during embryonic development, we have studied the expression pattern of Rab11 in mesoderm during muscle differentiation in Drosophila embryo. When dominant-negative or constitutively active Drosophila Rab11 proteins are expressed or Rab11 is reduced via double-stranded RNA in muscle precursors, they cause partial failure of myoblast fusion and show anomalies in the shape of the muscle fibres. Our results suggest that Rab11 plays no role in cell fate specification in muscle precursors but is required late in the process of myoblast fusion. This work was supported by grants from the DST (to J.K.R.) and SRF from ICMR, New Delhi (to T.B.).     

Serendipitous discovery of <Emphasis Type="Italic">Wolbachia</Emphasis> genomes in multiple <Emphasis Type="Italic">Drosophila</Emphasis>species

Background  

The Trace Archive is a repository for the raw, unanalyzed data generated by large-scale genome sequencing projects. The existence of this data offers scientists the possibility of discovering additional genomic sequences beyond those originally sequenced. In particular, if the source DNA for a sequencing project came from a species that was colonized by another organism, then the project may yield substantial amounts of genomic DNA, including near-complete genomes, from the symbiotic or parasitic organism.     

The first complete <Emphasis Type="Italic">Mag</Emphasis> family retrotransposons discovered in <Emphasis Type="Italic">Drosophila</Emphasis>

A retrotransposon of the Mag family was found in the Drosophila simulans genome for the first time. We also identified novel transposable elements representing the Mag family in seven Drosophila species. The high similarity between the 3’ and 5’ long terminal repeats in the found copies of transposable elements indicates that their retrotransposition has occurred relatively recently. Thus, the Mag family of retrotransposons is quite common for the genus Drosophila.     

Safeguarding genetic information in <Emphasis Type="Italic">Drosophila</Emphasis>

Eukaryotic cells employ a plethora of conserved proteins and mechanisms to ensure genome integrity. In metazoa, these mechanisms must operate in the context of organism development. This mini-review highlights two emerging features of DNA damage responses in Drosophila: a crosstalk between DNA damage responses and components of the spindle assembly checkpoint, and increasing evidence for the effect of DNA damage on the developmental program at multiple points during the Drosophila life cycle.     

Independent Origins of New Sex-Linked Chromosomes in the <Emphasis Type="Italic">melanica</Emphasis> and <Emphasis Type="Italic">robusta</Emphasis> Species Groups of <Emphasis Type="Italic">Drosophila</Emphasis>

Background  

Recent translocations of autosomal regions to the sex chromosomes represent important systems for identifying the evolutionary forces affecting convergent patterns of sex-chromosome heteromorphism. Additions to the sex chromosomes have been reported in the melanica and robusta species groups, two sister clades of Drosophila. The close relationship between these two species groups and the similarity of their rearranged karyotypes motivates this test of alternative hypotheses; the rearranged sex chromosomes in both groups are derived through a common origin, or the rearrangements are derived through at least two independent origins. Here we examine chromosomal arrangement in representatives of the melanica and the robusta species groups and test these alternative hypotheses using a phylogenetic approach.     

Recent advances in <Emphasis Type="Italic">Drosophila</Emphasis> genomics

A report on the 45th annual Drosophila Research Conference, Washington DC, USA, 23-28 March 2004.