Development of the nervous system Flashcards
What is neurulation?
Formation of the neural plate (when exoderm signals to the mesoderm)
Folding into neural groove
Convergence and closure of neural tube (CNS) or neural crest (PNS) - the seal is mediated by cadherins
What happens when neural tube closure is defective?
Anencephaly - unclosed head
Encephalocele - brain on outside
Describe the principles of development from blastomere
- Blastomere formed by cleavage of fertilised ovum
- Blastopore forms at dorsal lip
- Gastralation occurs when embryo moves cells around body
- Part of dorsal mesoderm starts to underlie the endoderm
- This sends signal to surrounding mesoderm which sends molecular signal to exoderm
What causes Spina bifida?
1- Altered folic acid metabolism
2- Causes decreased methylation of proteins or of lipids and molecules
3- Causes change in protein/gene expression
= neural tube defects
Importance of folate metabolism
-Serum folate enters via transporters forming 5-MeTHF
-MeTHF helps form vit B12 which changes methylation effect on DNA proteins and lipids
-Not enough B12 =
Teratogen (developmental defects)
Change in DNA synthesis
What does development of neural tube lead to?
Folds into hindbrain, midbrain and forebrain
How does the mesoderm induce neural cell fate?
Neural plate comes from ectoderm, the neuroectoderm needs to be induced by underlying mesoderm to gain neural fate.
When ectoderm cells stick together, signal BMP which preserves ectodermal fate.
The mesoderm induces neural cell fate by inhibiting BMP signalling in the ectoderm
What is lateral inhibition?
Initially all cells are equivalent, if one gets the upper hand it can supress its neighbours and can take on neural fate.
E.g Proneural cells surrounding each other with equal DELTA ( ligand )and NOTCH ( receptor)
If middle cell expressing more DETLA then surrounding express more NOTCH
Middle cell expresses more DELTA so has neural fate
What does loss of NOTCH signal cause?
Overproliferation of neural fate
