Download Drosophila melanogaster

Drosophila melanogaster
Source: Zdenék Berger
Mating
adult
Egg-laying
Life Cycle
pupa
(10 days)
Embryo
larva
Drosophila natural history
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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
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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”
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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
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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
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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?
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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