Drosophila melanogaster Source: Zdenék Berger

Mating adult Egg-laying Life Cycle (10 days) pupa 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 Worm Fly Mouse Human Genome (Mb) 4.6 150 3000 100 12 # Genes 4000 6000 19000 15000 30000? # Neurons (1) 302 10 5 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