Neural Patterning Flashcards
What is neural patterning?
formation of the different regions of the nervous systems
What are the neural patterning types?
anterior-posterior patterning
dorsal-ventral patterning
What are the general principles of neural patterning?
- The molecular mechanisms of patterning are conserved among different species
- Gradients of soluble proteins and patterns of transcription factor expression control pattern formation
- Certain factors can have different developmental effects depending on time and location of their action (BMP4)
- Generally, anterior-posterior patterning happens before dorsal-ventral patterning
What are morphogens?
Morphogens are factors that usually act in a gradient manner to determine the fate of cells
FGF?
it is a posteriorizing signal that is high in concentration at the tail; induces structures
wingless/wnt proteins?
it is a posteriorizing signal that is high in concentration at the tail; induces structures
BMP?
it is a dorsalizing signal; induces structures on dorsal side (spine?)
hedgehog/sonic hedgehog
it is a ventralizing signal
Hox gene?
transcription factors that regulate expression of other genes
What does the anterior mesoderm become?
Head
What does the posterior mesoderm become?
trunk and tail
2 step induction method?
- mesoderm releases factors and starts to move underneath the ectoderm
- anterior neural forms first; posterior neural 2nd
What factors are more concentrated at the posterior end?
FGF, Wnt, and RA (retinoic acid)
Where was hox genes discovered?
drosophila
Principles of Hox gene organization and expression
- the lower the hox gene number, the more 3’ location on the chromosome
- the lower the number, the earlier in development the expression begins
- the lower the number, the more anterior expression begins
The regulated expression of hox genes provides a positional code for patterning in ______ and _____ ____
hindbrain; spinal cord
The hindbrain is segmented into what?
8 rhombomeres that correlate with expression boundaries of hox genes
What is main dorsalizing signals? What does it induce?
BMP-4 and -7 induce roof plate
What is main ventralizing signal? What does it induce?
sonic hedgehog(shh) induces floor plate
What produces DV inductive signals?
BMP is made from ectoderm then roof plate; shh is made from notochord then floor plate
gradients of __________ and patterns of _________________ control pattern formation
soluble proteins; transcription factor expression
What happens first AP patterning or DS patterning?
anterior-posterior
