Body Axes and Neurulation Flashcards
Cell migration and specification (gastrulation) are controlled by what?
FGF8 (made by primitive streak cells)….establishes expression of Nodal on LEFT side only (before gastrulation it’s symmetric)
Primary germ layers
Top to bottom:
Ectoderm
Mesoderm
Endoderm
What expresses genes for head formation and TF’s “cerebrus” and “lefty”?
AVE (anterior visceral endoderm)
Gene for movement of cells from primitive streak
Brachyury (T) gene
Gene for primitive streak formation
Nodal gene
Gene for body axis formation
Goosecoid gene
Gene for the formation of notochord
HNF-3β
Gene for head formation
Lim-1
Goosecoid gene overexpression
2 heads
What does T gene (brachyury) antagonize?
BMP-4
Absense of T (brachyury) gene → no lower body/very small
Activin gene inhibits what and is expressed on which side?
Inhibits Shh (sonic hedgehog) expression
Activin expressed on RIGHT, so it blocks Shh on the right
FGF8 induces expression of what?
Lefty2 (Lefty 1 expressed in forming neural tube)
5HT dependent on serotonin
5HT→FGF8→Nodal and Lefty2→PITX2
PITX2 does what?
TF responsible for establishing LEFT sidedness (defects can cause organs to be on opposite sides)
5HT is important in what?
Establishing laterality
Disruptions can result in situs inversus, dextrocardia and heart defects
↑ congenital heart defects in children born to mom’s who take antidepressants from selective serotonin reuptake inhibitors (SSRI’s)
Gene for Right-sided development
Snail
repressed by Nodal