Anterior posterior axis formation-the posterior signal

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Lecture 6

• Anterior posterior axis formation-the posterior
  signal
• Anterior posterior axis formation-down the
  hierarchy

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Lab 3
208 or 210 Phsp ftz D273-303 ry 226
Phsp ftz 3-413 ry
3
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.
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The mutant allele used for the engrailed and
wingless experiments was ftz13.
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Pole cell transplantation Mosaic analysis
Cellular Blastoderm
Egg chamber
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Example
pipe (pip)
Toll (Tll)
What cells, follicle or germ-line, are pipe and
Toll required in?
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Pole cell transplantation Mosaic analysis
OvoD
No eggs
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Pole cell transplantation Mosaic analysis
OvoD
Wild type
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Pole cell transplantation Mosaic analysis
OvoD
Wild type
Wild type
Active egg chamber get eggs produced
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(No Transcript)
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Toll
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pipe
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Posterior signal
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Three classes of maternal effect phenotypes
Nusslein-Volhard et al., Science 238, 1675-1681
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Nusslein-Volhard et al., Science 238, 1675-1681
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What was done to show that nanos was the best
candidate to encode the posterior signal?
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Pole cell formation
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Injection of oocyte cytoplasm
nanos
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Injection of nurse cell cytoplasm
nanos
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Injection of stage 10 cytoplasm
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Nanos isolation expression
Wang and Lehmann Cell 66, 637-647
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Nanos isolation localization
Wang and Lehmann Cell 66, 637-647
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Nanos isolation rescue
Wang and Lehmann Cell 66, 637-647
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Nanos and maternal Hunchback expression
Nanos
Hunchback
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Expression of Hunchback from maternal mRNA
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Nanos
Maternal Hunchback expression
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Larvae lacking both maternal and zygotic hb
exhibit a stronger phenotype
hb/hb
Irish et al., Nature 338, 646-648
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Larvae lacking both maternal and zygotic hb
exhibit a stronger phenotype
hb/hb
Pole cell transplantation
hb-
OvoD
mat hb-
hb/hb
hb
Irish et al., Nature 338, 646-648
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Larvae lacking both maternal and zygotic hb
exhibit a stronger phenotype
hb/hb
hb-
mat hb-
Irish et al., Nature 338, 646-648
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Maternal Hunchback is dispensable for normal
development
hb/hb
hb-
mat hb-
hb
Irish et al., Nature 338, 646-648
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Nanos phenotype
Irish et al., Nature 338, 646-648
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Nanos has no role when mat hb is removed
Pole cell transplantation
OvoD
hb
hb/hb nos/nos
mat nos- hb-
Irish et al., Nature 338, 646-648
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Two polar centers regulate Hunchback expression
Wharton and Struhl Cell 67, 955-967
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Nanos regulatory sequences in the 3 UTR of mat hb
Wharton and Struhl Cell 67, 955-967
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Hunchback expression
Wharton and Struhl Cell 67, 955-967
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Nanos represses bicoid translation
mRNA
protein
Wang and Lehmann Cell 66, 637-647
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What Nanos and Pumilio do to suppress Hunchback
Gilbert Developmental Biology 7th ed
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Microtubules and the transport of Nanos and
Bicoid mRNA
Gilbert Developmental Biology 7th ed
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Hunchback lacks anterior segments
Nusslein-Volhard and Wieschaus 1980 Nature 287,
795
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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
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Expression of some Gap proteins
HB
GTa
TLLa
Kr
Kni
TLLp
GTp
0
100 egg length
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Posterior signal is permissive because the
terminal protein Tailless supresses GT
expression. The termini provide polarity.
HB
TLLa
GT
Kr
Kni
Kni
TLLp
GT
0
100 egg length
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Hunchback gradient and the regulation of gap genes
HB
Kr
Kni
GTp
0
100 egg length
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Hunchback gradient and the regulation of gap genes
Regulatory rules
medium HB activates Kr medium HB represses
Kni low HB represses gtp
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Outcome of the regulatory rules
HB
GTp
Kr
Kni
0
100 egg length
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Expression of FTZ and EVE
Lawrence The making of a fly
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Eve stripe 2 regulatory element
Gilbert Developmental Biology 7th ed
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Stripe two element expression
lacZ
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HB
BCD
GTa
Kr
0
100 egg length
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HB
EVE stripe two
BCD
GTa
Kr
0
100 egg length
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Stripe 2 regulatory rules
BIC and HB activate EVE stripe 2 expression KR
and GT repress EVE stripe 2 expression
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Stripe 2 cis-regulatory elements
HB
KR
BCD
GT
lacZ
lacZ
lacZ
lacZ
lacZ
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HB
EVE stripe two
BCD
GTa
Kr
0
100 egg length
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Stripe 2 cis-regulatory elements
HB
KR
BCD
GT
lacZ
lacZ
lacZ
lacZ
lacZ
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Stripe 2 trans-regulatory factors
HB
KR
BCD
GT
lacZ
hb/hb
lacZ
gt/gt
lacZ
lacZ
Kr/Kr
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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
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Establishing wingless and engrailed expression
Gilbert Developmental Biology 7th ed
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Maintaining the boundary
Gilbert Developmental Biology 7th ed
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You are segmented but not all segments are equal.
Homeotic selector genes are required for
determining segmental identity.
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Homeosis Homeotic mutation
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Antennapedia can be misexpressed either by
spontaneous mutation or by genetic engineering.
Antenna to second leg transformation
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The classic Ultrabithorax phenotype the four
winged fly
wild type
Ubx
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(No Transcript)
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Proboscipedia
tarsus
pb
proboscis
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Homeotic gene complexes and expression
Gilbert Developmental Biology 7th ed