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Lecture 3
• Cell Biology of Drosophila Development
• Drosophila Genetics
• Screen for Zygotic Lethals
• Screen for Maternal Effect Mutants
Lab 3 Engrailed staining
Elyse will open the teaching lab at 9:00AM
Read instructions in manual and on the board in the lab
If you start at 9:00AM you can be finished by about 4:00PM
Get yourselves organized or it will be a very long day.
Next week’s reading
DiNardo paper is missing a page and pages 1222 and 1223 are reversed. Can get the missing page on the web site.
Cell Biology of Drosophila Development
Structure of the egg
Dorsal appendage
Chorion
VitellineMicropyle
Structure of the egg
Dorsal appendage
Chorion
VitellineMicropyle
D
V
A P
Syncytial blastoderm
2nd cleavage
Campos-Ortega and Hartenstein 1985
Syncytial blastoderm
9th cleavage
Campos-Ortega and Hartenstein 1985
Pole cells
Germ-line soma division
Cellular Blastoderm
Hartenstein 1993
Blastoderm fate map
Hartenstein 1993
Gastrulation 3 hours
Hartenstein 1993
2:50 h
3:40 h
4:20 h
Mesoderm and the ventral furrow
Hartenstein 1993
QuickTime™ and aYUV420 codec decompressor
are needed to see this picture.
QuickTime™ and aYUV420 codec decompressor
are needed to see this picture.
Gastrulation and germ band retraction
Flybase
Germ band retraction
7:20 h
9:20 h
10:20 h
Hartenstein 1993
Development of the Brain
Hartenstein 1993
The Drosophila life cycle represents the differentiation of two distinct forms: the larva and the Imago (adult).
Embryogenesis: differentiation of the larva
Metamorphosis:differentiation ofthe imago (adult)
Imaginal cells are the cellsof the adult or imago.
Kalthoff 2001
Origin and differentiation of Imaginal cells
Embryonic Origin Differentiation
The resulting Imago
Hartenstein 1993
Oogenesis
Kalthoff 2001
Yamashita, Y. M. et al. J Cell Sci 2005;118:665-672
GSC niches in the Drosophila ovary and testis
Development and structure of the Cyst
Ring canals
Kalthoff 2001
Oogenesis
Anterior
Posterior
Kalthoff 2001
Later stages of Oogenesis
A
PA
A
P
P
Haploid versus Diploid Genetics
Haploidgenetics
Diploidgenetics
Genetic organization of Drosophila
Y 1stX
2nd 3rd 4th
1% of genome
Most information on 1, 2 and 3 chromosomes
Males and females
XY or X0 maleX/A ratio 0.5
XX femaleX/A ratio 1
Properties of Balancer Chromosomes
• Multiple inversions to suppress the recovery of recombinants.
• Recessive visible markers
• Dominant visible marker(s)
• Second and Third balancers homozygous lethal; first chromosome balancers homozygous female sterile.
Balancers
chromosome First Second Third
name FMBasc
CyOSM
TM
Dominantmarkers
Bar Curly StubbleSerrateUltrabithorax
Balancer chromosomes
Balancer homolog
Both the balancer and homolog chromosomes segregateas single mendelian units: the chromosome is a stable geneticunit.
Maternal versus Zygotic genomes
Maternal genomeOogenesis
Zygote and Zygoticgenome
SpermPaternal genome
Screens for Pattern Formation Mutants
Zygotic lethal screens: screens for activities expressedfrom the zygotic genome required for correct pattern formation.
Maternal effect screens: screens for activities expressed from the maternal genome required for correct pattern formation.
Basic steps of a screen
1 Mutagenesis
2 Separating the mutant chromosomes
3 Amplifying the mutant chromosomes
4 Testing for mutant phenotypes
Zygotic screenF0
DTS91 pr cn sca/CyO virgin females X cn bw sp males
EMS
DTS91: dominant temperature sensitive mutationDies at 29 C.
CyO second chromosome balancer
cn bw mutant combination results in white eyes
Zygotic screenF0
X cn bw sp males
EMSMutagenesis
Generating the random pool of mutagenized chromosomes
Zygotic screenF0-F1
DTS91 pr cn sca/CyO virgin females X cn bw sp males
EMS
F0
DTS91 pr cn sca/CyO virgin females Xcn bw sp*/CyO
cn bw sp*/DTS91 pr cn sca
or
Individual males
* mutagenized chromosomeSet up 10,000 crosses
F1
Zygotic screenF0-F1
cn bw sp*/CyO
cn bw sp*/DTS91 pr cn sca
or
Individual males
Set up 10,000 crosses
F1 separating the mutant chromosomes
Zygotic screenF1-F2
DTS91 pr cn sca/CyO virgin females Xcn bw sp*/CyO
cn bw sp*/DTS91 pr cn sca
or
Individual males
* mutagenized chromosome
10,000 crosses
F1
29 C for 4 days
cn bw sp*/CyO
Males and femalesF2
5,764
Zygotic screenF1-F2
DTS91 pr cn sca/CyO virgin females X cn bw sp*/CyOF1
cn bw sp*/CyOF2
DTS91 pr cn sca/CyO CyO/CyODTS91 pr cn sca/ cn bw sp*
Zygotic screenF1-F2
DTS91 pr cn sca/CyO virgin females X cn bw sp*/CyOF1
cn bw sp*/CyOF2
DTS91 pr cn sca/CyO CyO/CyODTS91 pr cn sca/ cn bw sp*
Dead Dead Dead
Alive
Zygotic screenF1-F2
DTS91 pr cn sca/CyO virgin females Xcn bw sp*/CyO
cn bw sp*/DTS91 pr cn sca
orF1
29 C for 4 days
cn bw sp*/CyO
Males and femalesF2
F1-F2 amplifying the mutant chromosomes
Zygotic screenF2-F3
* mutagenized chromosome
cn bw sp*/CyO
Males and femalesF2
5,764
F3 Screen for vials that have no white eyed flies.
4,217
Zygotic screenF2-F3
* mutagenized chromosome
cn bw sp*/CyO
Males and femalesF2
5,764
F3 Screen for vials that have no white eyed flies.
4,217
F3 started the testing
F3 tests
The 4,217 F3 flies were allowed to lay eggs
CyO/CyO larvae die after hatching
Screen for >25% unhatched eggs
2,843 lines had > 25% unhatched eggs
Test for cuticle defects
272 lines had distinct cuticular changes
Complementation analysis
The 272 mutants identified 61 complementationgroups (genes).
Maternal effect screens
F0 F1 F2 F3
F0 F1 F2 F3
Egg
Maternalgenome
F4
Zygotic screen
Maternal screenMother
Dead embryo
Maternal effect screen
Trudi Schupbach screen on the second chromosome.
Beautiful design: avoids having to sort the flies and collect virgins once the mutagenized chromosomes have been separated.
Maternal effect screen
cn bw sp/ CyO DTS.513 virgins X cn bw males
EMSF0
Maternal effect screen
cn bw sp/ CyO DTS.513 virgins X cn bw males
EMS
F1cn bw*/ CyO DTS.513 virgins
Collect individual virgin female flies
Maternal effect screen
cn bw sp/ CyO DTS.513 virgins X cn bw males
EMS
F1cn bw*/ CyO DTS.513 virgins X Fs(2) D/ CyO DTS.513
Dominant female sterile
males
Maternal effect screen
F1cn bw*/ CyO DTS.513 virgins X Fs(2) D/ CyO DTS.513
males
genotypes females males
cn bw*/ CyO DTS.513
cn bw*/ Fs(2) D
Fs(2) D/ CyO DTS.513
F2
Maternal effect screen
F1cn bw*/ CyO DTS.513 virgins X Fs(2) D/ CyO DTS.513
males
genotypes females males
cn bw*/ CyO DTS.513 fertile
cn bw*/ Fs(2) D sterile
Fs(2) D/ CyO DTS.513 sterile
F2
Maternal effect screen
F1cn bw*/ CyO DTS.513 virgins X Fs(2) D/ CyO DTS.513
males
genotypes females males
cn bw*/ CyO DTS.513 fertile fertile
cn bw*/ Fs(2) D sterile fertile
Fs(2) D/ CyO DTS.513 sterile fertile
F2
Maternal effect screen
genotypes females males
cn bw*/ CyO DTS.513 fertile fertile
cn bw*/ Fs(2) D sterile fertile
Fs(2) D/ CyO DTS.513 sterile fertile
F2
Intermate
F3
29 C lay eggs and develop
Maternal effect screen
F3
29 C lay eggs and develop
genotypes phenotype
cn bw*/ CyO DTS.513
Fs(2) D/ CyO DTS.513
cn bw*/ Fs(2) D
cn bw*/ cn bw*
Maternal effect screen
F3
29 C lay eggs and develop
genotypes phenotype
cn bw*/ CyO DTS.513 dead
Fs(2) D/ CyO DTS.513 dead
cn bw*/ Fs(2) D viable
cn bw*/ cn bw* dead/viable?
Maternal effect screen
F3
29 C lay eggs and develop
genotypes phenotype
cn bw*/ Fs(2) D viable
cn bw*/ cn bw* dead/viable?
Of 10,842 established F3 lines
5,174 gave cn bw*/ cn bw* homozygous viable femalesThese were tested for sterility.
Maternal effect screen29 C lay eggs and develop
Of 18,782 established F3 lines
7,351 gave homozygous viable femalesThese were tested for sterility.
529 were sterile
Combination of numbers from a second screen
Maternal effect screen
Of these 529 mutants 136 laid normal looking eggs that did not develop normally.We are looking at the eggs in the F4 generations.
Maternal effect mutants
These 136 mutations identified 67 complementation groups.
Similar screens were performed on the second and third chromosomes.