Drosophila

Drosophila melanogaster

The use of the fruit fly Drosophila melanogaster as an animal model imparts many advantages for studying the molecular and cellular mechanisms of Parkinson’s Disease (PD) due to its short life span (30 days), small size (2.5 mm), short generation time (10 days), large number of progeny, high degree of conserved biological pathways due to comparable fly and human genomes and well-defined genetic & pharmacological techniques.  The completion of sequencing the Drosophila genome, expanding collection of mutant strains, development of RNA-interference technologies & targeted gene disruption techniques and transcriptional & proteome profiling studies all facilitated the amenability of the fly animal model to the study of PD¹.

The characteristic pathological lesions of PD contain inclusion bodies composed of intracellular protein aggregates called Lewy bodies, which are constituted of alpha-synuclein aggregates.  Post-translational modifications of alpha-synuclein have been shown to modulate aggregate formation and the severity of neuronal degeneration in several fly studies.  In addition to the underlying genetic factors that contribute to the pathogenesis of PD, environment factors have also been implicated.  Drug compounds that increase the production of reactive oxygen species (ROS), including paraquat and rotenone, has been shown to induce DA degeneration in several fly models.  These PD phenotypes are exemplified when the transgenic fly that harbors a mutation or gene implicated in familial PD are treated with ROS-inducing agents, indicating that both genetic and environmental risk factors are critical components that attribute to the etiology of PD. Drosophila transgenic studies can be extended to include quantitative proteomic and metabolic analyses to identify molecular pathways that are potentially perturbed in PD and could serve as potential biomarkers or diagnostic targets. These research findings indicate that the Drosophila system has enormous potential to gain a greater mechanistic understanding of PD through the identification of genes involved in familial PD, environmental agents involved in sporadic PD and the search of novel genes, pathways and compounds that may prevent PD pathogenesis.

 

Research Highlights:

• Phosphorylation of a key residue (Ser129) in alpha-synuclein was found to mediate neurotoxicity and inclusion formation²
• Alteration of Ser129 to a phosphorylation-incompetent residue attenuates alpha-synuclein toxicity (DA cell loss), while mutation of Ser129 to a residue to mimic phosphorylation enhanced alpha-synuclein toxicity²
• Alpha-synuclein induced phenotypes can be rescued through the inhibition of the histone deacetylase SIRT2 (protection against DA cell death)³, co-expression of the Cu/Zn superoxide dismutase (protection against both DA neuronal loss & locomotor disabilities)⁴ or co-expression of kinase PINK1 (loss of climbing ability)⁵
• Quantitative proteome analysis of transgenics expressing human alpha-synuclein found that proteins associated with cellular metabolism and signaling were differentially expressed⁶
• RNAi-mediated inhibition of the fly DJ-1 homologue (DJ-1 alpha) resulted in the cellular accumulation of ROS, hypersensitivity to oxidative stress and dysfunction/degeneration of both DA and photoreceptor neurons, which is supressed by phosphatidylinositol 3-kinase (PI3K)/Akt-signaling expression⁷
• Loss-of-function DJ-1 beta transgenics demonstrated an extended survival of DA neurons, resistance to paraquat stress and sensitivity to hydrogen peroxide treatment, while DJ-1 alpha overexpression in DA neurons is sufficient to confer protection against paraquat⁸
• DJ-1 alpha and DJ-1 beta double knockout flies display selective sensitivity to the ROS-inducing agents, paraquat and rotenone⁹
• Expression of human LRRK2 or LRRK2-G2019S, the most common mutation associated with PD, in Drosophila neurons produced adult-onset selective loss of DA neurons, locomotor dysfunction and early mortality¹⁰
• PINK1 (a PTEN-induced putative kinase 1) deficient flies exhibit DA neuronal degeneration, locomotive defects, mitochondrial defects and increased sensitivity to oxidative stress, which can be partially suppressed or rescued by the expression of Parkin(an ubiquitin E3 ligase)^11,12,13
• PINK1 and Parkin null mutants indicate a role for the PINK1-Parkin pathway in promoting mitochondrial fission by negatively regulating Mitofusin & Optic atrophy 1 function and inhibiting fusion by positively regulating Dynamin-related protein 1^14,15,16

 

References:

1              Whitworth AJ, Wes PD, Pallanck LJ. Drosophila models pioneer a new approach to drug discovery for Parkinson's disease. Drug Discov Today. 2006 Feb;11(3-4):119-26. {Abstract}

2              Chen L, Feany MB. Alpha-synuclein phosphorylation controls neurotoxicity and inclusion formation in a Drosophila model of Parkinson disease. Nat Neurosci. 2005 May;8(5):657-63. {Abstract}

3              Outeiro TF, Kontopoulos E, Altmann SM, Kufareva I, Strathearn KE, Amore AM, Volk CB, Maxwell MM, Rochet JC, McLean PJ, Young AB, Abagyan R, Feany MB, Hyman BT, Kazantsev AG. Sirtuin 2 inhibitors rescue alpha-synuclein-mediated toxicity in models of Parkinson's disease. Science. 2007 Jul 27;317(5837):516-9. {Abstract}

4              Botella JA, Bayersdorfer F, Schneuwly S. Superoxide dismutase overexpression protects dopaminergic neurons in a Drosophila model of Parkinson's disease. Neurobiol Dis. 2008 Apr;30(1):65-73. {Abstract}

5              Todd AM, Staveley BE. Pink1 suppresses alpha-synuclein-induced phenotypes in a Drosophila model of Parkinson's disease. Genome. 2008 Dec;51(12):1040-1046. {Abstract}

6              Xun Z, Kaufman TC, Clemmer DE. Proteome response to the panneural expression of human wild-type alpha-synuclein: a Drosophila model of Parkinson's disease. J Proteome Res. 2008 Sep;7(9):3911-21. {Abstract}

7              Yang Y, Gehrke S, Haque ME, Imai Y, Kosek J, Yang L, Beal MF, Nishimura I, Wakamatsu K, Ito S, Takahashi R, Lu B. Inactivation of Drosophila DJ-1 leads to impairments of oxidative stress response and phosphatidylinositol 3-kinase/Akt signaling. Proc Natl Acad Sci U S A. 2005 Sep 20;102(38):13670-5. {Abstract}

8              Menzies FM, Yenisetti SC, Min KT. Roles of Drosophila DJ-1 in survival of dopaminergic neurons and oxidative stress. Curr Biol. 2005 Sep 6;15(17):1578-82. {Abstract}

9              Meulener M, Whitworth AJ, Armstrong-Gold CE, Rizzu P, Heutink P, Wes PD, Pallanck LJ, Bonini NM. Drosophila DJ-1 mutants are selectively sensitive to environmental toxins associated with Parkinson's disease. Curr Biol. 2005 Sep 6;15(17):1572-7. {Abstract}

10            Liu Z, Wang X, Yu Y, Li X, Wang T, Jiang H, Ren Q, Jiao Y, Sawa A, Moran T, Ross CA, Montell C, Smith WW. A Drosophila model for LRRK2-linked parkinsonism. Proc Natl Acad Sci U S A. 2008 Feb 19;105(7):2693-8. {Abstract}

11            Park J, Lee SB, Lee S, Kim Y, Song S, Kim S, Bae E, Kim J, Shong M, Kim JM, Chung J. Mitochondrial dysfunction in Drosophila PINK1 mutants is complemented by parkin. Nature. 2006 Jun 29;441(7097):1157-61. {Abstract}

12            Clark IE, Dodson MW, Jiang C, Cao JH, Huh JR, Seol JH, Yoo SJ, Hay BA, Guo M. Drosophila pink1 is required for mitochondrial function and interacts genetically with parkin. Nature. 2006 Jun 29;441(7097):1162-6. {Abstract}

13            Yang Y, Gehrke S, Imai Y, Huang Z, Ouyang Y, Wang JW, Yang L, Beal MF, Vogel H, Lu B. Mitochondrial pathology and muscle and dopaminergic neuron degeneration caused by inactivation of Drosophila Pink1 is rescued by Parkin. Proc Natl Acad Sci U S A. 2006 Jul 11;103(28):10793-8. {Abstract}

14            Poole AC, Thomas RE, Andrews LA, McBride HM, Whitworth AJ, Pallanck LJ. The PINK1/Parkin pathway regulates mitochondrial morphology. Proc Natl Acad Sci U S A. 2008 Feb 5;105(5):1638-43. {Abstract}

15            Deng H, Dodson MW, Huang H, Guo M. The Parkinson's disease genes pink1 and parkin promote mitochondrial fission and/or inhibit fusion in Drosophila. Proc Natl Acad Sci U S A. 2008 Sep 23;105(38):14503-8. {Abstract}

16            Park J, Lee G, Chung J. The PINK1-Parkin pathway is involved in the regulation of mitochondrial remodeling process. Biochem Biophys Res Commun. 2009 Jan 16;378(3):518-23. {Abstract}