Neural Tube Development - Lecture 14 Flashcards
Stages in neural tube development
- Formation of thickened neural plate
- Shaping of neural plate
- Folding of neural plate
- Formation of the neural tube
Shaping of the neural plate
Convergent extension - ectodermal cells migrate toward midline and elongate on the anterior-posteriior axis
Planar cell polarity - cells become oriented along an axis in flat pane
- Dishevelled (posteriorly)
- Prickle (anteriorly)
- asymmetry may be with Wnt gradient
Folding of neural plate
Neural groove with neural folds
Median hinge point induced by notochord
- columnar cells take on a pyramidal shape
- lateral hinge points by apical constriction by actin filaments
- neural folds elevated
Formation of the neural tube
Fusion of the neural folds
Mediated by glycoconjugates
Begins in middle and extends out 21-22 days in
Closure in cranial and caudal
Day 23 - neuropores remain
What is oct-2 responcibility in neural tube segmentation?
Expressed in forebrain/midbrain region
Consistes of. Anterior visceral endoderm and prechordal plate
The hindbrain region is formed from what tanscription factor?
Gbx-2 is expressed in the anterior notochord and causes formation of the hindbrain region
An anterior-posterior gradient of the neural tube is established by what?
wnt-8
Isthmic organizer region
Between the boundries of Oct-2 and Gbx-2 region
Organization of midbrain and cerebellum
Releases wnt-1 and FGF-8 posteriorly which induced an anterior gradient of En-1 and posterior gradient of En-2
Anterior neural ridge signalling center
Important for organization of the telencephalon, parts of the diencephalon, olfactory area and pituitary gland
Secretes shh and FGF-8
Zona limitans signalling center
Organization of border between dorsal and ventral thalamus and secrete shh
Hindbrain is broken into how many rhombomeres? What factors induce which?
7 rhombomeres
Gbx-2 for R1, 2 and 3
Krox 20 for R3 and R5
Retinoic acid gradients for R4-R7
Kreisler and Hoxa-1 for R5
The hox gene expression is induced by retinotic acid
The caudal portion of the neural plate is a _____ _______ _______ and these cells are constinantly proliferating without differentiating this is due to transcription factor __________. What happens as the neural tube continues posterior development?
Stem cell zone
FGF-8
The stem cell zone cells fall out of of the zone and begin to differenctiate because of retinotic acid.
Retinoic acid blocks FGF-8 and Wnt-3a
