Date post: | 21-Dec-2015 |
Category: |
Documents |
View: | 218 times |
Download: | 0 times |
Neurulation
(see slides posted at end of DB5 ppt)
Inducer Responder
SignalingInducer Responder
Signals can actin a graded fashion
Setting up a signaling gradient:
the role of the wingless gene
Cells know theirpositions within the body anddifferentiateaccordingly
Anterior
Posterior
A- HairP- Bare Skin
segment
wild type
A = hair
P = bare skin
To set up this pattern, flies use the secreted protein Wingless to specify a posterior fate
segment
BePosterior!
Cells instruct one anothervia cell-cell signaling pathways
BePosterior!
Cell-cell signaling can be influenced by distance between cells
Yes Ma'am!
Pardon me?
Anterior: Low Wingless,Hairs
Posterior: High Wingless,Naked Cuticle
Wingless-expressing cellsWingless diffusesaway from the cellsthat secrete it
Wingless signaling specifies posterior cell fates in the ventral epidermis
arm mutantwild typeALL cells have anterior (hair) fate
A = hair
P = bare skin
Therefore, all cells can see wingless, and the concentration of wingless itself is what determines cell fate
Setting up a signal gradient
Turn on new genes!
Yes Ma'am!
Cell surface
Nucleus
Signal transduction moves information
from the cell surface to the nucleus and
other cellular targets
Turn on new genes; pass it on
Yes Ma'am!
Cell surface
Nucleus
Turn on new genes; pass it on Turn on
new genes; pass it on
Turn on new genes; pass it on
Signal transduction occurs through a series of steps
Geneticsrevealed theligand andproteins inthis signal
transductionpathway
Genetics can also position proteins within the signaling pathway
An example of the conservation of
key developmentalregulatory machinery
across animal phyla
flies mammalsSee Figure 3.28
Colon cancer, the second leading cause of cancer deaths in the U.S.,
results from inappropriate Wnt signaling
Polyps, the first stageIn tumor development
Insects:
A model systemto study hormonalcontrol ofpostembryonic development
Figure 15.9
Long range signaling
Vincent B. Wigglesworth
Discovered that blood-borne hormones control insect metamorphosis through experiments with a blood-sucking bug, Rhodnius prolixus
Blood-bornehormonesregulatethe timing ofmetamorphosis
Experiment #1
induces 1st instar larva to molt into very small adult
Experiment #2
Other hormones prevent metamorphosis
Experiment #3
Other hormones prevent metamorphosis
Transplant corpus allatum from 4th to 5th instar larva
Result: blocks metamorphosis, instead get “6th instar larva”
Adult
The cascade of hormonesregulating insectmetamophosis
Figure 15.16
PTTH
20E
Steroid hormones (ie 20E):hydrophobic signaling molecules
that can pass through the plasma membrane
20E
Figure 15.16
Most signals
Steroid hormones
(ie. 20E)
An insecticide produced by plants cause premature metamorphosis