Lecture 6
• Anterior posterior axis formation-the
posterior signal
• Anterior posterior axis formation-down
the hierarchy
Lab 3
208 or 210: P{hsp ftz D273-303 ry+}
226: P{hsp ftz 3-413 ry+}
Lab 5
166 refers to embryos laid by DH502 females
crossed with DH302 males.
167 refers to embryos laid by DH502 females
crossed with DH301 males.
Consult Hyduk and Percival-Smith for the
genotypes associated with the above strain
names. See Table 1 and Figure 5.
The mutant allele used for the engrailed
and wingless experiments was ftz13.
Pole cell transplantation
Mosaic analysis
Cellular Blastoderm
Egg chamber
Example
pipe (pip)
Toll (Tll)
What cells, follicle or germ-line, are pipe
and Toll required in?
Pole cell transplantation
Mosaic analysis
OvoD
No eggs
Pole cell transplantation
Mosaic analysis
Wild type
OvoD
Pole cell transplantation
Mosaic analysis
Wild type
OvoD
Wild type
Active egg chamber
get eggs produced
Toll
Genotype of follicle cells
lf
Genotype
of oocyte
pole cells
Tll
wt
Tll lf dorsalized dorsalized
wt wt
wt
pipe
Genotype of follicle cells
Genotype
of oocyte
pole cells
pipelf
wt
lf
pipe dorsalized wt
wt dorsalized wt
Posterior signal
Three classes of maternal effect phenotypes
Nusslein-Volhard et al., Science 238, 1675-1681
Nusslein-Volhard et al., Science 238, 1675-1681
What was done to show that nanos
was the best candidate to encode the
posterior signal?
Pole cell formation
Locus
Pole cells
nanos
+
pumilio
+
oskar
-
staufen
-
vasa
-
tudor
-
valois
-
Injection of oocyte cytoplasm
nanos
Injection of nurse cell cytoplasm
nanos
Injection of stage 10 cytoplasm
Genotype of Oocyte
donor
% rescue
wild-type
40
Nurse cell
% rescue
66
nanos
0
0
pumilio
33
56
oskar
74
66
staufen
52
87
vasa
72
95
valois
31
100
tudor
9
35
Nanos isolation
expression
Wang and Lehmann Cell 66, 637-647
Nanos isolation
localization
Wang and Lehmann Cell 66, 637-647
Nanos isolation
rescue
Wang and Lehmann Cell 66, 637-647
Nanos and maternal Hunchback expression
Nanos
Hunchback
Expression of Hunchback from maternal mRNA
Nanos
Maternal Hunchback expression
Larvae lacking both maternal and zygotic hb exhibit a
stronger phenotype
hb/hb
Irish et al., Nature 338, 646-648
Larvae lacking both maternal and zygotic hb exhibit a
stronger phenotype
hb/hb
Pole cell
transplantation
hbhb/hb
OvoD
mat hbhb+
Irish et al., Nature 338, 646-648
Larvae lacking both maternal and zygotic hb exhibit a
stronger phenotype
hb/hb
hbmat hb-
Irish et al., Nature 338, 646-648
Maternal Hunchback is dispensable for normal
development
hb/hb
hbmat hbhb+
Irish et al., Nature 338, 646-648
Nanos phenotype
Irish et al., Nature 338, 646-648
Nanos has no role when mat hb is removed
Pole cell
transplantation
hb/hb
nos/nos
hb+
OvoD
Irish et al., Nature 338, 646-648
mat nos- hb-
Two polar centers regulate Hunchback expression
Wharton and Struhl Cell 67,
955-967
Nanos regulatory sequences in the 3’ UTR of mat hb
Wharton and Struhl Cell 67,
955-967
Hunchback expression
Wharton and Struhl Cell 67,
955-967
Nanos represses bicoid translation
mRNA
protein
Wang and Lehmann Cell 66, 637-647
What Nanos and Pumilio do to suppress Hunchback
Gilbert Developmental Biology 7th ed
Microtubules and the transport of Nanos and Bicoid mRNA
Gilbert Developmental Biology 7th ed
Hunchback lacks anterior segments
Nusslein-Volhard
and Wieschaus
1980 Nature 287,
795
Gap proteins
Transcription factors
Hunchback is a morphogen
Delineate blocks of pattern along the A-P axis
Gap information used to set up the striped
expression of pair-rule genes
Expression of some Gap proteins
HB
TLLa
100%
GTa
Kr
egg length
Kni
GTp
TLLp
0%
Posterior signal is permissive because the terminal
protein Tailless supresses GT expression. The
termini provide polarity.
HB
TLLa
100%
GT Kni
Kr
egg length
Kni
GT
TLLp
0%
Hunchback gradient and the regulation of gap genes
HB
Kr
100%
egg length
Kni
GTp
0%
Hunchback gradient and the regulation of gap genes
Regulatory rules
medium [HB] activates Kr
medium [HB] represses Kni
low [HB] represses gtp
Outcome of the regulatory rules
HB
Kr
100%
egg length
Kni
GTp
0%
Expression of FTZ and EVE
Lawrence The making of a fly
Eve stripe 2 regulatory element
Gilbert Developmental Biology 7th ed
Stripe two element expression
lacZ
HB
BCD
GTa
100%
Kr
egg length
0%
HB
EVE stripe two
BCD
GTa
100%
Kr
egg length
0%
Stripe 2 regulatory rules
BIC and HB activate EVE stripe 2 expression
KR and GT repress EVE stripe 2 expression
Stripe 2 cis-regulatory elements
BCD
KR
GT
HB
lacZ
lacZ
lacZ
lacZ
lacZ
HB
EVE stripe two
BCD
GTa
100%
Kr
egg length
0%
Stripe 2 cis-regulatory elements
BCD
KR
GT
HB
lacZ
lacZ
lacZ
lacZ
lacZ
Stripe 2 trans-regulatory factors
BCD
KR
GT
HB
lacZ
lacZ
hb/hb
lacZ
gt/gt
lacZ
Kr/Kr
Expression of FTZ and EVE
The expression of pair-rule gene is the first evidence
of segmentation; however, the cellular blastoderm
embryo is not overtly segmented morphologically.
Prepattern.
Lawrence The making of a fly
Establishing wingless and engrailed expression
Gilbert Developmental Biology 7th ed
Maintaining the boundary
Gilbert Developmental Biology 7th ed
You are segmented but not all segments are equal.
Homeotic selector genes are required for
determining segmental identity.
Homeosis
Homeotic mutation
Antennapedia can be misexpressed either by spontaneous
mutation or by genetic engineering.
Antenna to second leg transformation
The classic Ultrabithorax phenotype:
the four winged fly
wild type
Ubx
Proboscipedia
pb
tarsus
proboscis
Homeotic gene complexes and expression
Gilbert Developmental Biology 7th ed