Institute of Cellular and Developmental Biology

Vári, Greece

Institute of Cellular and Developmental Biology

Vári, Greece

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Kadas D.,National and Kapodistrian University of Athens | Tzortzopoulos A.,Institute of Cellular and Developmental Biology | Skoulakis E.M.C.,Institute of Cellular and Developmental Biology | Consoulas C.,National and Kapodistrian University of Athens
Journal of Neuroscience | Year: 2012

Development of neural circuitry relies on precise matching between correct synaptic partners and appropriate synaptic strength tuning. Adaptive developmental adjustments may emerge from activity and calcium-dependent mechanisms. Calcium/calmodulin-dependent protein kinase II (CaMKII) has been associated with developmental synaptic plasticity, but its varied roles in different synapses and developmental stages make mechanistic generalizations difficult. In contrast, we focused on synaptic development roles of CaMKII in a defined sensory-motor circuit. Thus, different forms of CaMKII were expressed with UAS-Gal4 in distinct components of the giant fiber system, the escape circuit of Drosophila, consisting of photoreceptors, interneurons, motoneurons, and muscles. The results demonstrate that the constitutively active CaMKII-T287D impairs development of cholinergic synapses in giant fiber dendrites and thoracic motoneurons, preventing light-induced escape behavior. The locus of the defects is postsynaptic as demonstrated by selective expression of transgenes in distinct components of the circuit. Furthermore, defects among these cholinergic synapses varied in severity, while the glutamatergic neuromuscular junctions appeared unaffected, demonstrating differential effects of CaMKII misregulation on distinct synapses of the same circuit. Limiting transgene expression to adult circuits had no effects, supporting the role of misregulated kinase activity in the development of the system rather than in acutely mediating escape responses. Overexpression of wild-type transgenes did not affect circuit development and function, suggesting but not proving that the CaMKII-T287D effects are not due to ectopic expression. Therefore, regulated CaMKII autophosphorylation appears essential in central synapse development, and particular cholinergic synapses are affected differentially, although they operate via the same nicotinic receptor. © 2012 the authors.


Gouzi J.Y.,Institute of Cellular and Developmental Biology | Moressis A.,Institute of Cellular and Developmental Biology | Moressis A.,National and Kapodistrian University of Athens | Walker J.A.,Harvard University | And 4 more authors.
PLoS Genetics | Year: 2011

Anaplastic Lymphoma Kinase (Alk) is a Receptor Tyrosine Kinase (RTK) activated in several cancers, but with largely unknown physiological functions. We report two unexpected roles for the Drosophila ortholog dAlk, in body size determination and associative learning. Remarkably, reducing neuronal dAlk activity increased body size and enhanced associative learning, suggesting that its activation is inhibitory in both processes. Consistently, dAlk activation reduced body size and caused learning deficits resembling phenotypes of null mutations in dNf1, the Ras GTPase Activating Protein-encoding conserved ortholog of the Neurofibromatosis type 1 (NF1) disease gene. We show that dAlk and dNf1 co-localize extensively and interact functionally in the nervous system. Importantly, genetic or pharmacological inhibition of dAlk rescued the reduced body size, adult learning deficits, and Extracellular-Regulated-Kinase (ERK) overactivation dNf1 mutant phenotypes. These results identify dAlk as an upstream activator of dNf1-regulated Ras signaling responsible for several dNf1 defects, and they implicate human Alk as a potential therapeutic target in NF1. © 2011 Gouzi et al.


Kalajdzic P.,University of Belgrade | Kalajdzic P.,University of Crete | Oehler S.,Institute of Cellular and Developmental Biology | Oehler S.,Indian Institute of Technology Delhi | And 6 more authors.
PLoS ONE | Year: 2012

Insecticide resistance is a worldwide problem with major impact on agriculture and human health. Understanding the underlying molecular mechanisms is crucial for the management of the phenomenon; however, this information often comes late with respect to the implementation of efficient counter-measures, particularly in the case of metabolism-based resistance mechanisms. We employed a genome-wide insertional mutagenesis screen to Drosophila melanogaster, using a Minos-based construct, and retrieved a line (MiT[w-]3R2) resistant to the neonicotinoid insecticide Imidacloprid. Biochemical and bioassay data indicated that resistance was due to increased P450 detoxification. Deep sequencing transcriptomic analysis revealed substantial over- and under-representation of 357 transcripts in the resistant line, including statistically significant changes in mixed function oxidases, peptidases and cuticular proteins. Three P450 genes (Cyp4p2, Cyp6a2 and Cyp6g1) located on the 2R chromosome, are highly up-regulated in mutant flies compared to susceptible Drosophila. One of them (Cyp6g1) has been already described as a major factor for Imidacloprid resistance, which validated the approach. Elevated expression of the Cyp4p2 was not previously documented in Drosophila lines resistant to neonicotinoids. In silico analysis using the Drosophila reference genome failed to detect transcription binding factors or microRNAs associated with the over-expressed Cyp genes. The resistant line did not contain a Minos insertion in its chromosomes, suggesting a hit-and-run event, i.e. an insertion of the transposable element, followed by an excision which caused the mutation. Genetic mapping placed the resistance locus to the right arm of the second chromosome, within a ~1 Mb region, where the highly up-regulated Cyp6g1 gene is located. The nature of the unknown mutation that causes resistance is discussed on the basis of these results. © 2012 Kalajdzic et al.


Kalajdzic P.,University of Belgrade | Kalajdzic P.,University of Crete | Markaki M.,Foundation for Research and Technology Hellas | Oehler S.,Institute of Cellular and Developmental Biology | And 2 more authors.
Food and Chemical Toxicology | Year: 2013

Certain xenobiotics have the capacity to induce the expression of genes involved in various biological phenomena, including insecticide resistance. The induction potential of different chemicals, among them different insecticides, has been documented for a number of insect species. In this study, we have analyzed the induction potential of Imidacloprid, a widely used member of the neonicotinoid insecticide family. Genes Cyp6g1 and Cyp6a2, known to be involved in the resistance of mutant Drosophila melanogaster line MiT[W-]3R2 to Imidacloprid and DDT were included in the analyzed sample. We find that Imidacloprid does not induce expression of the analyzed genes. © 2013 Elsevier Ltd.


Walker J.A.,Harvard University | Walker J.A.,Massachusetts General Hospital | Gouzi J.Y.,Harvard University | Gouzi J.Y.,Institute of Cellular and Developmental Biology | And 10 more authors.
PLoS Genetics | Year: 2013

Neurofibromatosis type 1 (NF1), a genetic disease that affects 1 in 3,000, is caused by loss of a large evolutionary conserved protein that serves as a GTPase Activating Protein (GAP) for Ras. Among Drosophila melanogaster Nf1 (dNf1) null mutant phenotypes, learning/memory deficits and reduced overall growth resemble human NF1 symptoms. These and other dNf1 defects are relatively insensitive to manipulations that reduce Ras signaling strength but are suppressed by increasing signaling through the 3′-5′ cyclic adenosine monophosphate (cAMP) dependent Protein Kinase A (PKA) pathway, or phenocopied by inhibiting this pathway. However, whether dNf1 affects cAMP/PKA signaling directly or indirectly remains controversial. To shed light on this issue we screened 486 1st and 2nd chromosome deficiencies that uncover >80% of annotated genes for dominant modifiers of the dNf1 pupal size defect, identifying responsible genes in crosses with mutant alleles or by tissue-specific RNA interference (RNAi) knockdown. Validating the screen, identified suppressors include the previously implicated dAlk tyrosine kinase, its activating ligand jelly belly (jeb), two other genes involved in Ras/ERK signal transduction and several involved in cAMP/PKA signaling. Novel modifiers that implicate synaptic defects in the dNf1 growth deficiency include the intersectin-related synaptic scaffold protein Dap160 and the cholecystokinin receptor-related CCKLR-17D1 drosulfakinin receptor. Providing mechanistic clues, we show that dAlk, jeb and CCKLR-17D1 are among mutants that also suppress a recently identified dNf1 neuromuscular junction (NMJ) overgrowth phenotype and that manipulations that increase cAMP/PKA signaling in adipokinetic hormone (AKH)-producing cells at the base of the neuroendocrine ring gland restore the dNf1 growth deficiency. Finally, supporting our previous contention that ALK might be a therapeutic target in NF1, we report that human ALK is expressed in cells that give rise to NF1 tumors and that NF1 regulated ALK/RAS/ERK signaling appears conserved in man. © 2013 Walker et al.


Skoulakis E.M.C.,Institute of Cellular and Developmental Biology | Mudher A.,University of Southampton
Biochemical Society Transactions | Year: 2010

Tauopathies are a clinically diverse group of neurodegenerative dementias involving perturbations of the level or phosphorylation state of themicrotubule-binding axonal protein tau. Despite intense effort in recent years, the precise role of tau in the pathology of the various behaviourally and neuropathologically distinct tauopathies, the mechanisms of tau toxicity and the potential functional interaction of tau and amyloid in Alzheimer's disease remain elusive. Nevertheless, novel observations regarding the various aspects of taumisregulation-dependent pathogenesis are emerging from various cellular, vertebrate and invertebrate animal models and are supported by new clinical data. This Focused Meeting brought together scientists working on tau and tauopathies from different disciplines and various experimental models. The aim was to enhance our understanding of the protein itself and disorders associated with its misregulation through synergy. ©The Authors.


Papanikolopoulou K.,Institute of Cellular and Developmental Biology | Kosmidis S.,Institute of Cellular and Developmental Biology | Grammenoudi S.,Institute of Cellular and Developmental Biology | Skoulakis E.M.C.,Institute of Cellular and Developmental Biology
Biochemical Society Transactions | Year: 2010

The heterogeneous pathology of tauopathies and the differential susceptibility of different neuronal types to WT (wild-type) and mutant tau suggest that phosphorylation at particular sites rather than hyperphosphorylation mediates toxicity or dysfunction in a cell-type-specific manner. Pan-neuronal accumulation of tau in the Drosophila CNS (central nervous system) specifically affected the MBs (mushroom body neurons), consistent with neuronal type-specific effects. The MB aberrations depended, at least in part, on occupation of two novel phosphorylation sites: Ser238 and Thr 245. The degree of isoform-specific MB aberrations was paralleled by defects in associative learning, as blocking putative Ser238 and Thr245 phosphorylation yielded structurally normal, but profoundly dysfunctional, MBs, as animals accumulating the mutant protein exhibited strongly impaired associative learning. Similarly dysfunctional MBs were obtained by temporally restricting tau accumulation to the adult CNS, which also altered the tau phosphorylation pattern. Our data clearly distinguish tau-dependent neuronal degeneration and dysfunction and suggest that temporal differences in occupation of the same phosphorylation sites are likely to mediate these distinct effects of tau. ©The Authors.


Papafotiou G.,Institute of Cellular and Developmental Biology | Papafotiou G.,University of Crete | Oehler S.,Institute of Cellular and Developmental Biology | Savakis C.,Institute of Cellular and Developmental Biology | And 3 more authors.
Research in Microbiology | Year: 2011

The maternally inherited obligatory intracellular bacterium Wolbachia is a reproductive parasite of many insect species. Wolbachia evades the host immune system, uses the mitotic apparatus to ensure infection of daughter cells, migrates through the host to the gonads and causes reproductive phenotypes, most commonly cytoplasmic incompatibility (CI), i.e. incompatibility of sperm from infected males and eggs from uninfected females. Due to the interconnected facts that Wolbachia is not ex vivo culturable and that no established transformation system exists, virtually nothing is known about Wolbachia-host interactions at the macromolecular level. Intriguingly, the Wolbachia genome codes for an unusually high number of ankyrin repeat (ANK) proteins. ANKs mediate protein-protein interactions in many different contexts. More common in eukaryotes, they also occur in prokaryotes. Some intracellular pathogenic bacteria export ANK effector proteins to the host cytoplasm. This makes the Wolbachia ANK genes candidates for mediating interactions with host cells. We quantified expression of ANK genes of Wolbachia strain wMel in adult gonads and detected host sex-specific regulation of two wMel ANK genes in the gonads in two different backgrounds. Regulation was tissue-specific and independent of host background. We further analyzed expression of their homologues in strains wAu and wRi and found regulation only in wAu. Regulation was tissue-specific and there was no correlation between regulation of these genes and the ability of a strain to induce CI. © 2011 Institut Pasteur.


PubMed | Institute of Cellular and Developmental Biology
Type: Journal Article | Journal: PLoS genetics | Year: 2011

Anaplastic Lymphoma Kinase (Alk) is a Receptor Tyrosine Kinase (RTK) activated in several cancers, but with largely unknown physiological functions. We report two unexpected roles for the Drosophila ortholog dAlk, in body size determination and associative learning. Remarkably, reducing neuronal dAlk activity increased body size and enhanced associative learning, suggesting that its activation is inhibitory in both processes. Consistently, dAlk activation reduced body size and caused learning deficits resembling phenotypes of null mutations in dNf1, the Ras GTPase Activating Protein-encoding conserved ortholog of the Neurofibromatosis type 1 (NF1) disease gene. We show that dAlk and dNf1 co-localize extensively and interact functionally in the nervous system. Importantly, genetic or pharmacological inhibition of dAlk rescued the reduced body size, adult learning deficits, and Extracellular-Regulated-Kinase (ERK) overactivation dNf1 mutant phenotypes. These results identify dAlk as an upstream activator of dNf1-regulated Ras signaling responsible for several dNf1 defects, and they implicate human Alk as a potential therapeutic target in NF1.


PubMed | Institute of Cellular and Developmental Biology
Type: Journal Article | Journal: Neurobiology of disease | Year: 2011

Cellular and organismal iron storage depends on the function of the ferritin protein complex in insects and mammals alike. In the central nervous system of insects, the distribution and relevance of ferritin remain unclear, though ferritin has been implicated in Drosophila models of Alzheimers and Parkinsons disease and in Aluminum-induced neurodegeneration. Here we show that transgene-derived expression of ferritin subunits in glial cells of Drosophila melanogaster causes a late-onset behavioral decline, characterized by loss of circadian rhythms in constant darkness and impairment of elicited locomotor responses. Anatomical analysis of the affected brains revealed crystalline inclusions of iron-loaded ferritin in a subpopulation of glial cells but not significant neurodegeneration. Although transgene-induced glial ferritin expression was well tolerated throughout development and in young flies, it turned disadvantageous at older age. The flies we characterize in this report contribute to the study of ferritin in the Drosophila brain and can be used to assess the contribution of glial iron metabolism in neurodegenerative models of disease.

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