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Drosophila melanogaster Source: Zdenék Berger Mating adult Egg-laying Life Cycle pupa (10 days) Embryo larva Drosophila natural history • • • • • Originated in Africa Probably spread by human activity Now found most places where we live Likes compost, rotting fruit, yeast Some features conserved, others a reflection of its life strategy • Harmless (mostly) • Most lab strains derived from isolates collected before 1940’s • Strains collected subsequently have P transposable elements and can’t easily be used Model Organisms - a trainspotter’s guide E. coli Yeast Genome (Mb) 4.6 12 # Genes 4000 6000 # Neurons 0 (1) Worm Fly Mouse Human 100 150 3000 3000 19000 15000 30000? 302 5 10 30000? 10 11 Where our pet flies live… Mice - 75c/day 150k$/yr Flies ~ 20k$/yr (consumables and labour) Can’t be stored frozen :-( Source: John Roote What are flies useful for? Fly pushing Early 1900’s - Drosophila contributes to our understanding of heredity Mid 1900’s - Grows in popularity among developmental biologists Homozygous lethal mutations can be kept indefinitely as heterozygous balanced stocks 1970’s - 1980’s - Molecular biology, cloning of Hsp, Hox 1970’s - 1980’s - Large screens for developmental mutants 1982 - Transformation by injection of marked P transposable element into syncytial embryos; transgenic flies identified by marker in F1 1988 - Easy mobilisation of P made possible by stable transposase-producing strains Recent articles from PubMed C.J. O’Kane (2003). Seminars in Cell and Developmental Biology 14:3-10. Source: Claude Everaerts What’s different? • More gene redundancy in humans & mammals • Some organisation of tissues and organs • Cardiovascular system • Acquired immunity (antibody response) • We’re studying them, instead of them studying us Insertional mutagenesis: many ways to kill a gene… Fly Gene Disruption Projects • • • • • • • • Based on transposable element insertion Allows further local mutagenesis Non-directed - like Venter’s sequencing strategy Not random ~ 15000 target genes include ~ 4000 vital genes Requires ~ 1 insertion per 8 kb Coverage perhaps 25% of that, more on their way into public domain FlyBase www.flybase.org Other ways to make “mutants” • • • • • • EMS - still has its attractions Targeted knockouts for reverse genetics Imprecise excisions for reverse genetics RNAi for reverse or forward genetics Deletion kits in defined backgrounds Ask a fellow flypusher Getting round early lethality • GAL4 x UAS-X for targeted expression Can be used for regulated RNAi expression GAL4 enhancer traps Getting round early lethality • GAL4 x UAS-X for targeted expression • Enhancer/suppressor screens Identifying genes in receptor tyrosine kinase signalling - screening for enhancers of sevenlessts Getting round early lethality • GAL4 x UAS-X for targeted expression • Enhancer/suppressor screens • Mitotic clones (using FLP recombinase) Mutant screens using mitotic clones Getting round early lethality • • • • • GAL4 x UAS-X for targeted expression Enhancer/suppressor screens Mitotic clones (using FLP recombinase) Temperature-sensitive point mutations RNAi screens in cultured cells Shared biology - shared diseases • • • • • • Cancer Ageing Neurodegeneration Infectious disease Models for disease vectors Behaviour Flies and “your” disease • Do flies have disease-gene homologs? • Do flies have basic cellular processes related to the disease? • Be nice to a friendly fly geneticist The future? • • • • • • More insertions UAS-RNAi collections SNPs, better mapping of point mutations Temperature-sensitive alleles for cell biology Screens take more work in flies than in worms Some things only possible in flies and not worms physiology, some development, some cell biology • “Hopping in” takes about $20k investment, or a friendly fly lab to drop in on