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Flashcards in Ventralization of the neural tube Deck (12)
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What is happening to the notochord at the same time that the neural plate/neural tube is forming

Notochord comes to lie at the ventral side at the midline of the neural tube


What does an ectopic notochord give rise to

Different signalling creates a secondary floor plate/ secondary set of motor neurons


What is the secreted factor from notochord/ floorplate in drosophila

Hedgehog - sonic hedgehog in vertebrates


Where is Shh found in the neural tube

Acts as a morphogen - high concentration at the ventral side of the tube - diffuses to dorsal side at low concentrations


What does Shh cause in progenitor cells

Causes them to produce transcription factors which confer ventral neural tube identities, progenitors will ultimately give rise to to cells that differentiate into ventral neurons


How do morphogen gradients used to establish progenitor domains

Made up of proliferating bands of cells - established through opposing morphogen gradients - Over time these differentiate and move laterally to form the defined neurons of the spinal cord, they then send out axons


What is the Hh signalling pathway

Ptc is a membrane receptor that, when not bound by Hh is inhibiting the action of another membrane bound protein, Smo
When inhibited Smo can't act on Gli2/3 which in the absence of Hh are in their repressor form so enter the nucleus and prevent gene activation


Where is Shh expressed in vertabrates

Along the whole A-P axis and is always ventral


How does Shh signalling intersect with the HOX code

Intersects with the HOX code that gives A-P segmentation
This means that motor neurons develop at the ventral region of the spinal cord


What neurons develop ventrally in the hindbrain

A small cluster of serotonergic neurons


What neurons develop ventrally in the midbrain

Dopaminergic neurons of the substantia nigra form


How does Shh signalling cause differing neuron development

Differing concentration gradient of Shh