Biology 3338A Lecture Notes - Lecture 12: Neural Plate, Surface Ectoderm, Sonic Hedgehog

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24 Jan 2015
Department
14-12-14
1
NEURAL INDUCTION AND PATTERNING Gilbert 333-344
Ectoderm instructed to form epidermis or neural
-different body regions induce different neural
tissues
(related to underlying endoderm, notochord, etc)
Neurulation
Gastrulation and neurulation are continuous
Notochord will form from the dorsal lip mesoderm
Ectoderm is folding to form a tube from anterior to posterior
Mesoderm through the dorsal lip is secreting the molecules noggin, etc. to ectoderm
Forming neural tube from ectoderm
Ectoderm forms many different things
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14-12-14
2
Primary neurulation
- formation of neural plate & shaping of neural plate
- bending of neural plate and formation of neural groove
- closure of neural groove to form neural tube
Formation and shaping of neural plate
dorsal mesoderm signals ectodermal cells to elongate into columnar neural
plate cells
plate lengthen along A-P axis
-need border regions of presumptive epidermis to form tube
ant
L R dorsal meso
ecto
noggin
Bending
-hinge region forms through cell contact
-in birds and mammals medial hinge point cells (MHP) form anterior to
Henson’s node -MHP anchored to notochord -> inductive signals
-surrounding surface ectoderm pushes
towards midline
-2 other hinge points form
-dorsolateral hinge points (DLHP)
-hinge points have characteristic
wedge shaped cells
Form plate, bend the plate, close the plate
Lateral to dorsal mesoderm are paraxial mesoderm, etc.
Signals to the paraxial and to the ectoderm to form a plate like structure, neural plate
Form neural plate above the notochord
Now hedgehog is involved
Undergo apical constriction to form a V
The apex of the cell constricts and causes the bend (creating medial hinge point)
In mammals and birds this is occurring anterior to posterior of Hensen’s node
Cells involuting at H node for the MHP
Lateral pressure that causes other cells to bend forming dorsolateral hinge points (DLHP)
Bringing the 2 apical pieces together
Closure then occurs to form the tube
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