Download Model 1: Observing and Modeling Neurulation

Development, SPR15
A POGIL exercise developed by Dr. A. Schivell
Nemhauser/Crowe
Model 1: Observing and Modeling Neurulation
Watch the "Chick Neurulation" video carefully several times. You are looking down on the
ectoderm. The anterior of the animal is to the right.
1. Describe the general cell movements in neurulation briefly.
Sheets of cells fold up and come together on the "outside" of the embryo.
2. Flatten your clay into a sheet to represent the cells of the ectoderm. Copy the folding that
you see in the videos. Eventually separate the invaginated part from the overlying part.
a. What structure does this folding eventually produce? the neural tube
b. What will that become in the adult organism? the brain and spinal cord (central NS)
19. Draw a cross section of the ectoderm once neurulation is complete. Top should be dorsal,
bottom ventral, sides left and right. (Imagine cutting your clay model in half, left to right).
Label your diagram with skin and neural tissues.
Skin
Neural
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Development, SPR15
A POGIL exercise developed by Dr. A. Schivell
Model 2: Neurulation Experiments
Nemhauser/Crowe
This model shows "normal" (WT) neurulation at the top, then several experiments where two
critical signaling molecules (noggin and BMP-4) have been altered (Exp. 1-4) or where parts of
the embryo have been removed (Exp. 5-7). Embryos on the left are pre-neurulation and on the
right are post-neurulation. You are shown the three embryonic germ layers on the left
(top=ectoderm, middle=mesoderm, and bottom=endoderm).
WT
Exp. 1
Add inhibitors of both
noggin and BMP-4
Exp. 2
Add inhibitor of the
signal molecule "BMP-4"
Exp. 3
Add inhibitor of the signal
molecule "noggin"
Exp. 4
Add extra "noggin"
Exp. 5
Exp. 6
Exp. 7
2
Development, SPR15
A POGIL exercise developed by Dr. A. Schivell
Nemhauser/Crowe
3. Two signals, noggin and BMP-4, work together during neurulation to determine which
parts of the ectoderm become skin and which parts become neural. Use experiments 1-4 for
the following questions.
a. What is the "default" state of the ectoderm? (Hint: no signal...) neural
b. Determine which signal prevents neural tube formation and explain your answer:
BMP-4 prevents neural tube
4. a. Using the data from experiments 5-7, determine where the signal comes from to initiate
neurulation. (Pick one from each group)
group 1:
group 2:
- mesoderm
- ectoderm
- midline of layer (along the A->P axis)
- endoderm
- sides of layer (left and right)
b. Which signal is most likely released by the cells that you chose in 'a'? How do you know?
noggin!
c. Which of the following schemes best represents the interaction between the signaling
molecules?
-noggin activates BMP-4
-BMP-4 activates noggin
-noggin inhibits BMP-4
-BMP-4 inhibits noggin
5. Propose a hypothesis for why the endoderm does not respond to the signals in the same
manner as the ectoderm.
Endoderm must not have receptors for noggin
6. The cells that make noggin are called the "notochord".
a. In what layer can you find the notochord? mesoderm
b. Describe the role of the notochord during this phase of development in a few words:
Notochord secretes noggin to induce neural tube formation in the overlying ectoderm
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Development, SPR15
A POGIL exercise developed by Dr. A. Schivell
Nemhauser/Crowe
AT HOME. These are practice questions to do at home next week after the Chick Embryo Lab.
You are observing embryos in culture (removed from the egg and growing in nutrient-rich
media). Pre-gastrulation, everything has proceeded normally in all cases. Consider each
scenario (a-e) separately. Write a "+" in the box under each developmental process that will
proceed NORMALLY.
Hensen’s
node
forms
Three
embryonic
layers form
Notochord
forms
Neural
tube
forms
Example: No mutations or treatments
+
+
+
+
a. Both copies of the gene encoding the
chordin protein have an early stop codon
at the third amino acid.
+
+
+
+
+
+
+
+/-
b. The embryo has the same mutations as
in Part a. You also transplant the cells of a
Hensen’s node from a normal embryo to
the mutant one
c. You add a chemical that binds and
prevents noggin from functioning,
immediately after the primitive groove
forms.
d. Both copies of the sonic hedgehog
receptor gene are mutated so that the
receptor does not bind its signal molecule.
+
e. The embryo has the same mutations as
in Part d. You also transplant a normal
Hensen’s node into the mutant embryo.
+
f. You have another wild-type (not mutant) embryo. When it reaches this stage,
you add the chemical from Part c. In the picture, circle the region of the embryo
that should continue to develop NORMALLY.
g. In the embryo in "f", which of the following will NEVER be
found in the chick? (Circle ALL that apply)
Somites
Tail
Anus
Eye
Mouth
Posterior Intestinal Portal
Hensen's
Node
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