The document discusses three key signaling pathways that pattern the neural tube during development: the Sonic hedgehog pathway, Wnt pathway, and BMPs (Bone Morphogenetic Proteins). It reviews how these three signals interact to establish dorsal-ventral patterning and regulate neurogenesis in the neural tube. Specifically, it describes how BMP gradients appear first to modulate Wnt levels and how the interplay between Wnt and Shh concentrations regulates patterning at the transcriptional level.

1. Neural Tube Patterning
A tale of three signals
Dorsal–Ventral Patterning of the Neural Tube: A Tale of Three Signals
Gwenvael Le Dre au, Elisa Mart
Developmental Neurobiology,2012.
Harsha Kumar, Kalyanee Shirlekar, Agrim Saini, Raunak Dev

2. What are the three signals?
http://scienceblogs.co
m/pharyngula/2007/0
5/04/we-have-thebrains-of-worms/

3. Sonic Hedgehog pathway (ssg)
Review
Pattern formation in the
vertebrate neural tube: a
sonic hedgehog
morphogen-regulated
transcriptional
network, Development
, 2008.
Eric Dessaud1, Andrew P.
McMahon2,* and James

5. Wnt Pathway
http://www.wormbook.or
g/chapters/www_wntsign
aling/wntsignaling.html

6. Over-expression of Wnt
in Roof plate cells

7. BMPs- Dorsal Patterning and
Neurogenesis
BMPs –Signaling Pathway

8. BMP4 KNOCKOUT

9. BMP 4
• Knockout in chick- Roof
Plate is not formed
properly.
• Required for dorsal
patterning.
• Reduction in dI1 neurons.
• Compensation of dIs not
observed.
• Required in neurogenesis.
BMP 7
• Knockout in chick- Identity
of Roof Plate is conserved.
• Not required for dorsal
patterning.
• Reduction in dI1, dI3, dI5
neurons
• Compensation of dIs not
observed.
• Required in neurogenesis

10. Conclusion
• The current model of describes a hierarchical
role of each of the three morphogens in the
DV patterning of neural tube
• BMP gradients seem to appear first , know to
modulate Wnt family levels.
• The interplay in conc. of Wnt and Shh
regulates patterning at the transcription
level, as seen at the Gli3 locus.

11. Further Directions
• Mechanism by which the “cells integrate these
global activities to produce a harmonious
response”
• To understand how a neural progenitor
manages to simultaneously sort information
for both its identity and behavior from a same
signaling pathway.