BB Lecture 3 Embryology and Neurulation Flashcards
What is otx2?
A transcription factor that is essential for the formation of all ANTERIOR neural structures
What happens to a otx2 -/- mutant?
No head development!
Pax6
A-P for forebrain; induced by fibroblast growth factor (FGF); represses emx2
Emx2
A-P for forebrain; induced by FGF; represses pax6
Hox genes
A-P for whole embryo; determines rhombomere identity in hindbrain
Shh
dorsal ventral axis
bmp
dorsal ventral axis polarity. BLOCKING BMP allows ectodermal cells to assume neuronal identity
totipotent
cells that can differentiate into anything from all three germ layers as well as extraembryonic tissues
pluripotent
a cell that differentiates to cells from 3 germ layers but NOT extra embryonic tissue
multipotent
progenitor cells that can give rise to cells from multipled but LIMITED number of lineages (think myeloid progenitor cells)
robo-3
example of receptor at growth cone that decides where axons grow; robo-3 mutant in humans = person can’t abduct their eyes
Sperry’s Frog
after lesion AND misplacement (rotation of frogs eye) axons grow back to where they were before originally, suggesting that the receptors on the axons induce growth towards same spots
EphrinA
repellant for axon guidance (posterior tectum)
EphBs
attractant for axon guidance (anterior tectum)
neurotrophins
signals secreted by target molecule/organ that allows neurons to survive; limited amount so only limited amount of neurons survive
how many neurons are made in embryo?
much more than what actually survives
what is the significance of there being a limited quanity of neurotrophin secreted by target organs/cells?
The fittest neurons outcompete other neurons for those neurotrophins in order to survive
What happens if you alter the pax6-emx2 ratio?
abnormal development of A-P FOREBRAIN
Rhombomere
9 rhombomeres in all; formed in hindbrain; gives rise to cranial nerves (since hindbrain is brain stem); controlled by hox genes
What happens to neural tube in Shh mutant?
No differentiation or maldevelopment of midline structures
Lack of hox genes in zebrafish
No cranial nerve differentiation (remember hox genes help differentiate rhombomeres)
inside-out maturation of cortex
Refers to the phenomenon of how EXCITATORY neurons are made (newest cells migrate closer to pia via radial glia, and older cells remain at bottom of ventricle)
Where are inhibitory interneurons made?
generated in the ventral telencephalon and migrate to the cortex
How do you get Lissencephaly?
You get the mutation of the Lis1 gene which is responsible for cortical formation of neurons; leads to smooth brain
What happens when you get a dcx (doublecortin) mutant?
double cortex problem (double layering of the cortex) a problem with neuronal migration and development in the cortical areas
Holoprosencephaly
Defect of forebrain development due to inhibition of pax6 and aberrant expression of shh…basically A-P and D-V patterning; cyclopia
