A Drosophila model of Friedreich ataxia with CRISPR/Cas9 insertion of GAA repeats in the frataxin gene reveals in vivo protection by N-acetyl cysteine.

Friedreich ataxia (FA) is caused by GAA repeat expansions in the first intron of FXN, the gene encoding frataxin, which results in decreased gene expression. Thanks to the high degree of frataxin conservation, the Drosophila melanogaster fruitfly appears as an adequate animal model to study this disease and to evaluate therapeutic interventions. Here, we generated a Drosophila model of FA with CRISPR/Cas9 insertion of approximately 200 GAA in the intron of the fly frataxin gene fh. These flies exhibit a developmental delay and lethality associated with decreased frataxin expression. We were able to bypass preadult lethality using genetic tools to overexpress frataxin only during the developmental period. These frataxin-deficient adults are short-lived and present strong locomotor defects. RNA-Seq analysis identified deregulation of genes involved in amino-acid metabolism and transcriptomic signatures of oxidative stress. In particular, we observed a progressive increase of Tspo expression, fully rescued by adult frataxin expression. Thus, Tspo expression constitutes a molecular marker of the disease progression in our fly model and might be of interest in other animal models or in patients. Finally, in a candidate drug screening, we observed that N-acetyl cysteine improved the survival, locomotor function, resistance to oxidative stress and aconitase activity of frataxin-deficient flies. Therefore, our model provides the opportunity to elucidate in vivo, the protective mechanisms of this molecule of therapeutic potential. This study also highlights the strength of the CRISPR/Cas9 technology to introduce human mutations in endogenous orthologous genes, leading to Drosophila models of human diseases with improved physiological relevance.

Genetic Screen in Adult Drosophila Reveals That dCBP Depletion in Glial Cells Mitigates Huntington Disease Pathology through a Foxo-Dependent Pathway.

Huntington's disease (HD) is a progressive and fatal autosomal dominant neurodegenerative disease caused by a CAG repeat expansion in the first exon of the huntingtin gene (HTT). In spite of considerable efforts, there is currently no treatment to stop or delay the disease. Although HTT is expressed ubiquitously, most of our knowledge has been obtained on neurons. More recently, the impact of mutant huntingtin (mHTT) on other cell types, including glial cells, has received growing interest. It is currently unclear whether new pathological pathways could be identified in these cells compared to neurons. To address this question, we performed an in vivo screen for modifiers of mutant huntingtin (HTT-548-128Q) induced pathology in Drosophila adult glial cells and identified several putative therapeutic targets. Among them, we discovered that partial nej/dCBP depletion in these cells was protective, as revealed by strongly increased lifespan and restored locomotor activity. Thus, dCBP promotes the HD pathology in glial cells, in contrast to previous opposite findings in neurons. Further investigations implicated the transcriptional activator Foxo as a critical downstream player in this glial protective pathway. Our data suggest that combinatorial approaches combined to specific tissue targeting may be required to uncover efficient therapies in HD.

Impact of Drosophila Models in the Study and Treatment of Friedreich's Ataxia.

Drosophila melanogaster has been for over a century the model of choice of several neurobiologists to decipher the formation and development of the nervous system as well as to mirror the pathophysiological conditions of many human neurodegenerative diseases. The rare disease Friedreich's ataxia (FRDA) is not an exception. Since the isolation of the responsible gene more than two decades ago, the analysis of the fly orthologue has proven to be an excellent avenue to understand the development and progression of the disease, to unravel pivotal mechanisms underpinning the pathology and to identify genes and molecules that might well be either disease biomarkers or promising targets for therapeutic interventions. In this review, we aim to summarize the collection of findings provided by the Drosophila models but also to go one step beyond and propose the implications of these discoveries for the study and cure of this disorder. We will present the physiological, cellular and molecular phenotypes described in the fly, highlighting those that have given insight into the pathology and we will show how the ability of Drosophila to perform genetic and pharmacological screens has provided valuable information that is not easily within reach of other cellular or mammalian models.

Frataxin inactivation leads to steroid deficiency in flies and human ovarian cells.

Friedreich ataxia (FA), the most common inherited autosomal-recessive ataxia in Caucasians, is characterized by progressive degeneration of the central and peripheral nervous system, hypertrophic cardiomyopathy and increased incidence of diabetes. FA is caused by a GAA repeat expansion in the first intron of the gene encoding frataxin, an evolutionarily conserved mitochondrial protein, which results in decreased gene expression. Ubiquitous inactivation of the fly frataxin ortholog dfh blocks the transition from larval to pupal stages. In this study, we show that this phenotype is due to ecdysteroid deficiency and that feeding larvae with the 20-hydroxyecdysone steroid hormone rescues this developmental blockage. In mammals, adrenodoxin, the ferredoxin FDX1, is an Fe-S-containing protein essential for the synthesis of various steroid hormones. We show here that the two fly ferredoxins, Fdxh and Fdxh2 (encoded by CG1319), are also involved in steroidogenesis. This provides a potent mechanism by which frataxin, known to be involved in Fe-S cluster biosynthesis, could affect steroidogenesis through reduced ferredoxin activity. Finally, we show that frataxin inactivation decreases progesterone synthesis in human KGN ovarian granulosa cells. Thus, the involvement of frataxin in steroid synthesis appears to be a conserved function of the protein from flies to human and our data suggest that steroidogenesis could be affected in FA patients.

Methylene blue rescues heart defects in a Drosophila model of Friedreich's ataxia.

Friedreich's ataxia (FRDA), the most common hereditary ataxia, is characterized by progressive degeneration of the central and peripheral nervous system, hypertrophic cardiomyopathy and a high risk of diabetes. FRDA is caused by abnormally low levels of frataxin, a highly conserved mitochondrial protein. Drosophila has been previously successfully used to model FRDA in various cell types, including neurons and glial cells. Here, we report the development of a Drosophila cardiac model of FRDA. In vivo heart imaging revealed profound impairments in heart function in frataxin-depleted Drosophila, including a strong increase in end-systolic and end-diastolic diameters and a decrease in fractional shortening (FS). These features, reminiscent of pathological phenotypes in humans, are fully rescued by complementation with human frataxin, suggesting conserved cardiac functions of frataxin between the two organisms. Oxidative stress is not a major factor of heart impairment in frataxin-depleted flies, suggesting the involvement of other pathological mechanisms notably mitochondrial respiratory chain (MRC) dysfunction. Accordingly, we report that methylene blue (MB), a compound known to act as an alternative electron carrier that bypasses mitochondrial complexes I-III, was able to prevent heart dysfunction. MB also partially rescued the phenotype when administered post-symptomatically. Analysis of MB derivatives demonstrates that only compounds with electron carrier properties are able to prevent the heart phenotype. Thus MB, a compound already used for several clinical applications, appears promising for the treatment of the heart dysfunctions that are a major cause of death of FRDA patients. This work provides the grounds for further evaluation of MB action in mammals.

dJun and Vri/dNFIL3 are major regulators of cardiac aging in Drosophila.

Cardiac aging is a complex process, which is influenced by both environmental and genetic factors. Deciphering the mechanisms involved in heart senescence therefore requires identifying the molecular pathways that are affected by age in controlled environmental and genetic conditions. We describe a functional genomic investigation of the genetic control of cardiac senescence in Drosophila. Molecular signatures of heart aging were identified by differential transcriptome analysis followed by a detailed bio-informatic analysis. This approach implicated the JNK/dJun pathway and the transcription factor Vri/dNFIL3 in the transcription regulatory network involved in cardiac senescence and suggested the possible involvement of oxidative stress (OS) in the aging process. To validate these predictions, we developed a new in vivo assay to analyze heart performance in various contexts of adult heart-specific gene overexpression and inactivation. We demonstrate that, as in mammals, OS plays a central role in cardiac senescence, and we show that pharmacological interventions impinging on OS slow heart senescence. These observations strengthen the idea that cardiac aging is controlled by evolutionarily conserved mechanisms, further validating Drosophila as a model to study cardiac senescence. In addition, we demonstrate that Vri, the ortholog of the vertebrate NFIL3/E4B4 transcription factor, is a major genetic regulator of cardiac aging. Vri overexpression leads to major heart dysfunctions, but its loss of function significantly reduces age-related cardiac dysfunctions. Furthermore, we unambiguously show that the JNK/AP1 pathway, the role of which in cardiac aging in mammals is controversial, is activated during cardiac aging and has a detrimental effect on cardiac senescence. This data-driven functional genomic analysis therefore led to the identification of key components of the Gene Regulatory Network of cardiac aging in Drosophila and may prompt to investigate the involvement of their counterparts in the cardiac aging process in mammals.

Glial overexpression of Tspo extends lifespan and protects against frataxin deficiency in Drosophila.

The translocator protein TSPO is an evolutionary conserved mitochondrial protein overexpressed in various contexts of neurodegeneration. Friedreich Ataxia (FA) is a neurodegenerative disease due to GAA expansions in the FXN gene leading to decreased expression of frataxin, a mitochondrial protein involved in the biosynthesis of iron-sulfur clusters. We previously reported that Tspo was overexpressed in a Drosophila model of this disease generated by CRISPR/Cas9 insertion of approximately 200 GAA in the intron of fh, the fly frataxin gene. Here, we describe a new Drosophila model of FA with 42 GAA repeats, called fh-GAAs. The smaller expansion size allowed to obtain adults exhibiting hallmarks of the FA disease, including short lifespan, locomotory defects and hypersensitivity to oxidative stress. The reduced lifespan was fully rescued by ubiquitous expression of human FXN, confirming that both frataxins share conserved functions. We observed that Tspo was overexpressed in heads and decreased in intestines of these fh-GAAs flies. Then, we further overexpressed Tspo specifically in glial cells and observed improved survival. Finally, we investigated the effects of Tspo overexpression in healthy flies. Increased longevity was conferred by glial-specific overexpression, with opposite effects in neurons. Overall, this study highlights protective effects of glial TSPO in Drosophila both in a neurodegenerative and a healthy context.

Drosophila CRISPR/Cas9 mutants as tools to analyse cardiac filamin function and pathogenicity of human FLNC variants.

Filamins are large proteins with actin-binding properties. Mutations in FLNC, one of the three filamin genes in humans, have recently been implicated in dominant cardiomyopathies, but the underlying mechanisms are not well understood. Here, we aimed to use Drosophila melanogaster as a new in vivo model to study these diseases. First, we show that adult-specific cardiac RNAi-induced depletion of Drosophila Filamin (dFil) induced cardiac dilatation, impaired systolic function and sarcomeric alterations, highlighting its requirement for cardiac function and maintenance of sarcomere integrity in the adult stage. Next, we introduced in the cheerio gene, using CRISPR/Cas9 gene editing, three missense variants, previously identified in patients with hypertrophic cardiomyopathy. Flies carrying these variants did not exhibit cardiac defects or increased propensity to form filamin aggregates, arguing against their pathogenicity. Finally, we show that deletions of the C-term part of dFil carrying the last four Ig-like domains are dispensable for cardiac function. Collectively, these results highlight the relevance of this model to explore the cardiac function of filamins and increase our understanding of physio-pathological mechanisms involved in FLNC-related cardiomyopathies. This article has an associated First Person interview with the first author of the paper.

G. sinense and P. notoginseng Extracts Improve Healthspan of Aging Flies and Provide Protection in A Huntington Disease Model.

In the last decades, the strong increase in the proportion of older people worldwide, and the increased prevalence of age associated degenerative diseases, have put a stronger focus on aging biology. In spite of important progresses in our understanding of the aging process, an integrative view is still lacking and there is still need for efficient anti-aging interventions that could improve healthspan, reduce incidence of age-related disease and, eventually, increase the lifespan. Interestingly, some compounds from traditional medicine have been found to possess anti-oxidative and anti-inflammatory properties, suggesting that they could play a role as anti-aging compounds, although in depth in vivo investigations are still scarce. In this study we used one the major aging model organisms, Drosophila melanogaster, to investigate the ability of four herb extracts (HEs: Dendrobium candidum, Ophiopogon japonicum, Ganoderma sinense and Panax notoginseng) widely used in traditional Chinese medicine (TCM) to slow down aging and improve healthspan of aged animals. Combining multiple approaches (stress resistance assays, lifespan and metabolic measurements, functional heart characterizations and behavioral assays), we show that these four HEs provide in vivo protection from various insults, albeit with significant compound-specific differences. Importantly, extracts of P. notoginseng and G. sinense increase the healthspan of aging animals, as shown by increased activity during aging and improved heart function. In addition, these two compounds also provide protection in a Drosophila model of Huntington's disease (HD), suggesting that, besides their anti-aging properties in normal individuals, they could be also efficient in the protection against age-related diseases.

A conditional pan-neuronal Drosophila model of spinocerebellar ataxia 7 with a reversible adult phenotype suitable for identifying modifier genes.

Spinocerebellar ataxia 7 (SCA7) is a neurodegenerative disease caused by a polyglutamine (polyQ) expansion in the ataxin 7 (ATXN7) protein, a member of a multiprotein complex involved in histone acetylation. We have created a conditional Drosophila model of SCA7 in which expression of truncated ATXN7 (ATXN7T) with a pathogenic polyQ expansion is induced in neurons in adult flies. In this model, mutant ATXN7T accumulated in neuronal intranuclear inclusions containing ubiquitin, the 19S proteasome subunit, and HSP70 (heat shock protein 70), as in patients. Aggregation was accompanied by a decrease in locomotion and lifespan but limited neuronal death. Disaggregation of the inclusions, when expression of expanded ATXN7T was stopped, correlated with improved locomotor function and increased lifespan, suggesting that the pathology may respond to treatment. Lifespan was then used as a quantitative marker in a candidate gene approach to validate the interest of the model and to identify generic modulators of polyQ toxicity and specific modifiers of SCA7. Several molecular pathways identified in this focused screen (proteasome function, unfolded protein stress, caspase-dependent apoptosis, and histone acetylation) were further studied in primary neuronal cultures. Sodium butyrate, a histone deacetylase inhibitor, improved the survival time of the neurons. This model is therefore a powerful tool for studying SCA7 and for the development of potential therapies for polyQ diseases.

Identification of cardioprotective drugs by medium-scale in vivo pharmacological screening on a Drosophila cardiac model of Friedreich's ataxia.

Friedreich's ataxia (FA) is caused by reduced levels of frataxin, a highly conserved mitochondrial protein. There is currently no effective treatment for this disease, which is characterized by progressive neurodegeneration and cardiomyopathy, the latter being the most common cause of death in patients. We previously developed a Drosophila melanogaster cardiac model of FA, in which the fly frataxin is inactivated specifically in the heart, leading to heart dilatation and impaired systolic function. Methylene Blue (MB) was highly efficient to prevent these cardiac dysfunctions. Here, we used this model to screen in vivo the Prestwick Chemical Library, comprising 1280 compounds. Eleven drugs significantly reduced the cardiac dilatation, some of which may possibly lead to therapeutic applications in the future. The one with the strongest protective effects was paclitaxel, a microtubule-stabilizing drug. In parallel, we characterized the histological defects induced by frataxin deficiency in cardiomyocytes and observed strong sarcomere alterations with loss of striation of actin fibers, along with full disruption of the microtubule network. Paclitaxel and MB both improved these structural defects. Therefore, we propose that frataxin inactivation induces cardiac dysfunction through impaired sarcomere assembly or renewal due to microtubule destabilization, without excluding additional mechanisms. This study is the first drug screening of this extent performed in vivo on a Drosophila model of cardiac disease. Thus, it also brings the proof of concept that cardiac functional imaging in adult Drosophila flies is usable for medium-scale in vivo pharmacological screening, with potent identification of cardioprotective drugs in various contexts of cardiac diseases.

Specific age-related signatures in Drosophila body parts transcriptome.

BACKGROUND: During the last two decades progress in the genetics of aging in invertebrate models such as C. elegans and D. melanogaster has clearly demonstrated the existence of regulatory pathways that control the rate of aging in these organisms, such as the insulin-like pathway, the Jun kinase pathway and the Sir2 deacetylase pathway. Moreover, it was rapidly shown that some of these pathways are conserved from yeast to humans. In parallel to genetic studies, genomic expression approaches have given us significant information on the gene expression modifications that occur during aging either in wild type or long-lived mutant animals. But most of the genomic studies of invertebrate models have been performed so far on whole animals, while several recent studies in mammals have shown that the effects of aging are tissue specific. RESULTS: We used oligonucleotide microarrays to address the specificities of transcriptional responses in aging Drosophila in head, thorax or whole body. These fly parts are enriched in transcripts that represent different and complementary sets of genes. We present evidence for both specific and common transcriptional responses during the aging process in these tissues. About half of the genes described as downregulated with age are linked to reproduction and enriched in gonads. Greater downregulation of mitochondrial genes, activation of the JNK pathway and upregulation of proteasome subunits in the thorax of aged flies all suggest that muscle may be particularly sensitive to aging. Simultaneous age-related impairment of synaptic transmission gene expression is observed in fly heads. In addition, a detailed comparison with other microarray data indicates that in aged flies there are significant deviations from the canonical responses to oxidative stress and immune stress. CONCLUSION: Our data demonstrates the advantages and value of regionalized and comparative analysis of gene expression in aging animals. Adding to the age-regulated genes already identified in whole animal studies, it provides lists of new regionalized genes to be studied for their functional role in the aging process. This work also emphasizes the need for such experiments to reveal in greater detail the consequences of the transcriptional modifications induced by aging regulatory pathways.

Methylene Blue Partially Rescues Heart Defects in a Drosophila Model of Huntington's Disease.

BACKGROUND: Huntington's disease (HD) is a Polyglutamine disease caused by the presence of CAG repeats in the first exon of Huntingtin (Htt), a large protein with multiple functions. In addition to neurodegeneration of specific brain regions, notably the striatum, HD also shows alterations in peripheral tissues, such as the heart, skeletal muscles or peripheral endocrine glands. Mutant Huntingtin (mHtt)-driven mitochondrial impairment may underlie some of the CNS and peripheral tissues dysfunctions, especially in tissues with high energy demand such as the heart. OBJECTIVE: The aim of this study is to characterize two new inducible Drosophila HD heart models and to assay the therapeutic potential of methylene blue in these HD models. METHODS: We report the construction of inducible Drosophila HD heart models, expressing two Nter fragments of the protein encompassing either exon 1 or the first 171 amino acids and the characterization of heart phenotypes in vivo. RESULTS: We show that both mHtt fragments are able to impair fly cardiac function with different characteristics. Additionally, expression of mHtt, which was limited to adulthood only, leads to mild heart impairment, as opposed to a strong and age-dependent phenotype observed when mHtt expression was driven during both developmental and adult stages. We report that treatment with methylene blue (MB), a protective compound in mitochondria-related diseases, partially protects the fly's heart against mHtt-induced toxicity, but does not rescue neuronal or glial phenotypes in other fly models of HD. This may be linked to its low penetration through the fly's blood-brain barrier. CONCLUSIONS: Our data suggest that improvement of mitochondrial function by MB, or related compounds, could be an efficient therapeutic strategy to prevent cardiac failure in HD patients.

Automated and portable solid phase extraction platform for immuno-detection of 17ß-estradiol in water.

A fully automated and portable system for solid phase extraction (SPE) has been developed for the analysis of the natural hormone 17ß-estradiol (E2) in environmental water by enzyme linked immuno-sorbent assay (ELISA). The system has been validated with de-ionized and artificial sea water as model samples and allowed for pre-concentration of E2 at levels of 1, 10 and 100 ng/L with only 100 ml of sample. Recoveries ranged from 24±3% to 107±6% depending on the concentration and sample matrix. The method successfully allowed us to determine the concentration of two seawater samples. A concentration of 15.1±0.3 ng/L of E2 was measured in a sample obtained from a food production process, and 8.8±0.7 ng/L in a sample from the Adriatic Sea. The system would be suitable for continuous monitoring of water quality as it is user friendly, and as the method is reproducible and totally compatible with the analysis of water sample by simple immunoassays and other detection methods such as biosensors.

A Yeast/Drosophila Screen to Identify New Compounds Overcoming Frataxin Deficiency.

Friedreich's ataxia (FA) is a rare neurodegenerative disease which is very debilitating for the patients who progressively lose their autonomy. The lack of efficient therapeutic treatment of the disease strongly argues for urgent need to search for new active compounds that may stop the progression of the disease or prevent the appearance of the symptoms when the genetic defect is diagnosed early enough. In the present study, we used a yeast strain with a deletion of the frataxin homologue gene as a model of FA cells in a primary screen of two chemical libraries, a fraction of the French National Chemical Library (5500 compounds) and the Prestwick collection (880 compounds). We ran a secondary screen on Drosophila melanogaster flies expressing reduced levels of frataxin during larval development. Half of the compounds selected in yeast appeared to be active in flies in this developmental paradigm, and one of the two compounds with highest activities in this assay partially rescued the heart dilatation phenotype resulting from heart specific depletion of frataxin. The unique complementarity of these two frataxin-deficient models, unicellular and multicellular, appears to be very efficient to select new compounds with improved selectivity, bringing significant perspectives towards improvements in FA therapy.

Hedgehog signal transduction proteins: contacts of the Fused kinase and Ci transcription factor with the kinesin-related protein Costal2.

BACKGROUND: Hedgehog signaling proteins play important roles in development by controlling growth and patterning in various animals including Drosophila and mammals. Hedgehog signaling triggers changes in responsive cells through a novel transduction mechanism that ultimately controls the transcription of specific target genes via the activity of zinc finger transcription factors of the Cubitus interruptus/GLI family. In flies, key Hedgehog signal transduction components have been identified including the kinesin-related protein Costal2, the serinethreonine kinase Fused, and the PEST-containing protein Suppressor of Fused. These proteins control Cubitus interruptus cleavage, nucleo-cytoplasmic localization and activation. In fly embryos, Costal2, Fused, Suppressor of Fused and Cubitus interruptus are associated in at least one cytoplasmic complex, which interacts with the microtubules in a Hedgehog-dependent manner. RESULTS: Here we identified and mapped direct interactions between Cos2, Fu, and Ci using an in vitro affinity assay and the yeast two-hybrid system. CONCLUSIONS: Our results provide new insights into the possible mechanism of the cytosolic steps of Hedgehog transduction.

Genome wide analysis of common and specific stress responses in adult drosophila melanogaster.

BACKGROUND: During their life, multicellular organisms are challenged with oxidative stress. It is generated by several reactive oxygen species (ROS), may limit lifespan and has been related to several human diseases. ROS can generate a wide variety of defects in many cellular components and thus the response of the organism challenged with oxidative stress may share some features with other stress responses. Conversely, in spite of recent progress, a complete functional analysis of the transcriptional responses to different oxidative stresses in model organisms is still missing. In addition, the functional significance of observed transcriptional changes is still elusive. RESULTS: We used oligonucleotide microarrays to address the specificities of transcriptional responses of adult Drosophila to different stresses induced by paraquat and H2O2, two oxidative stressors, and by tunicamycin which induces an endoplasmic reticulum (ER) stress. Both specific and common responses to the three stressors were observed and whole genome functional analysis identified several important classes of stress responsive genes. Within some functional classes, we observed that isozymes do not all behave similarly, which may reflect unsuspected functional specificities. Moreover, genetic experiments performed on a subset of lines bearing mutations in genes identified in microarray experiments showed that a significant number of these mutations may affect resistance of adult Drosophila to oxidative stress. CONCLUSIONS: A long term common stress response to paraquat- or H2O2-induced oxidative stresses and ER stress is observed for a significant number of genes. Besides this common response, the unexpected complexity of the stress responses to oxidative and ER stresses in Drosophila, suggest significant specificities in protective properties between genes associated to the same functional classes. According to our functional analysis, a large part of the genome may play a role in protective mechanisms against oxidative stress in Drosophila.

Control of oxidative stress resistance by IP3 kinase in Drosophila melanogaster.

Oxidative damage is thought to be a major causal factor of aging, and is implicated in several human pathologies such as Alzheimer's and Parkinson's diseases. Nevertheless the genetical determinants of in vivo oxidative stress response are still poorly understood. To identify cellular components whose deregulation leads to oxidative stress resistance, we performed a genetic screen in Drosophila melanogaster. We thus identified in this screen Drosophila Inositol 1,4,5-triphosphate kinase I (D-IP3K1), a Drosophila gene homologous to mammalian IP3Ks. In vertebrates, IP3Ks phosphorylate the second messenger Inositol 1,4,5-triphosphate (IP3) to produce Inositol 1,3,4,5 tetrakiphosphate (IP4). IP3 binding to its receptor (IP3R) triggers Ca(2+) release from the endoplasmic reticulum (ER) to the cytosol, whereas IP4 physiological role remains elusive. We show here that ubiquitous overexpression of D-IP3K1 confers resistance of flies to H(2)O(2)- but not to paraquat-induced oxidative stress. Additional genetic analysis with other members of IP3 and IP4 signaling pathways led us to propose that the D-IP3K1 protective effect is mainly mediated through the reduction of IP3 level (which probably results in reduced Ca(2+) release from internal stores), rather than through the rise of IP4 level.

Mitochondrial electron transport chain dysfunction during development does not extend lifespan in Drosophila melanogaster.

Since the initial identification of reactive oxygen species (ROS) as the major factor in aging, many studies have provided evidence for the central role of mitochondria in longevity. A few years ago, an unexpected finding showed that the inactivation of the mitochondrial respiratory chain (MRC) in Caenorhabditis elegans, during the developmental stages only, extended lifespan. Activation of this mitochondrial pathway affecting aging (MIT) is associated with several phenotypic features: increased longevity, increased time of development, decreased fertility/fecundity and reduced adult size. Here, we investigated this pathway in another model organism, Drosophila melanogaster. To assess the role of mitochondrial activity in the Drosophila aging process, we partially inactivated the MRC using RNA interference (RNAi) during larval stages. Developmental perturbation of the respiratory process prolonged development, increased lethality during developmental stage, reduced both fecundity and fertility and slightly reduced individual weight. However, in contrast to the nematode, this genetic intervention either shortened or had no effect on lifespan, depending on the level of gene inactivation. Thus, the effects of MRC disruption during development on aging differ between species. We discuss the possible origins of such differences.

The steroid hormone receptor EcR finely modulates Drosophila lifespan during adulthood in a sex-specific manner.

The steroid hormone ecdysone influences Drosophila lifespan. Longevity is extended in mutants deficient for ecdysone synthesis or mutants of the ecdysone receptor (EcR). However, the underlying mechanisms remain unclear. Here we conditionally inactivated EcR by RNA interference or expression of dominant negative forms, using the RU486 inducible system. A mild ubiquitous inactivation of EcR during adulthood was sufficient to slow the aging of male flies, whereas a stronger EcR inactivation decreased longevity. Surprisingly, ubiquitous inactivation of EcR strongly decreased female lifespan. This deleterious effect was suppressed in sterile ovo(D1) mutant females, suggesting that EcR represses a negative signal for lifespan produced in ovaries. These results reveal a complex adult and sex-specific control of lifespan by steroid signalling in Drosophila.