Lecture_March_02 - The central nervous system The...

The central nervous system
• The development of the neural tube
• Establishement of a multilayered
central nervous system
• Differentiation of neurons

I. Formation of the Neural Tube
ventral
Movie: neurulation in Xenopus

Primary neurulation
(most parts of body)
Neural plate
Neural
fold
Neural
tube
ectoderm
Neural
Crest
cells

1. Neural induction
dissociated ectodermal
cells that normally
give rise to epidermis
neural tissue
gastrula
In the absence of inhibitory signals, the default fate for an
ectodermal cell is to become a neural cell.
a. Inhibitory signals

TGF- β -family proteins (e.g.BMP-4) function as inhibitory
signals to prevent neural development.
epithelial
cell
neural
cell
ectodermal
cell
BMP4

b. Disinhibition: the role of positive signals
Fig. 4.16, p114, Wolpert
Conclusion: Dorsal mesoderm produces neuralizing signals.

-Noggin and Chordin
BMP4
Dorsal mesoderm
ectoderm
a. BMP4 prevents ectoderm from forming
neural tissue.