Lecture 9: Nervous system induction and symmetry Flashcards
Describe the development of the notochord in the early embryo.
- cells come from the primitive node
- precursors migrate anteriorly
- notochord cells fuse with the flanking endodermal cells and for a neurenteric canal which then separates from the endoderm and forms a neural cord
Describe the relationship of Nodal to the establishment of the anteroposterior axis, and indicate the role of Lefty 1 and Cer 1 in this process.
Lefty and Cer 1 are the signaling molecules that target nodal to block the expression of nodal in the anterior epiblast and makes it go posteriorly to from the primitive streak
How is Wnt3 related to Nodal?
Induces expression
What signaling molecules are involved in the inhibition of posterior structures?
Cerebrus-like
DKK-1
What signaling molecules from the primitive node are involved in neural induction?
Noggin and Chordin
What are the origin and effects of transcription factors Goosecoid and Brachyury with regard to the early primitive streak?
Goosecoid is from the primitive node and activates genes
Brachyury is from the primitive streak and helps to form the notochord
What is the source and the role of signaling molecules Cerebrus-like and DKK-1 in the development of the anterior-posterior axis?
They come from the anterior visceral endoderm and inhibit the development of posterior structures
What genes are targeted by Goosecoid?
Chrodin and noggin which are neural inducers
What are the effects of Foxa-2 on the early primitive streak stage?
Helps to make it
In the late primitive streak stage, what signaling molecule induces axial structures?
Shh
In the late primitive streak stage, what signaling molecule is necessary for normal head formation?
Cerebrus related 1
In the late primitive streak stage, what signaling molecules are needed for neural induction, and what is their origin?
From the notochord: noggin, chordin, and shh
In the late primitive streak stage, what signaling molecules released from the primitive streak activate Hox genes?
Retinoic acid
Wnt
FGF
What are the classical markers of the organizer region in vertebrates?
Chordin, Goosecoid, and Fox-2
Define determination
process where a cell or part of an embryo becomes restricted to one developmental pathway. becomes committed to a cell line
Define differentiations
Complex of changes involved in the progressive specialization of structure and function; luxury
What is nodal’s role in asymmetry
symmetry breaking molecule in the left side of the embryo
What is Lefty-1’s role in asymmetry?
blocks the diffusion of the molecules to the right side
What are the 4 stages in neural tube development?
- formation of the thickened neural plate
- shaping of the neural plate
- folding of the neural plate
- formation of the neural tube
Why is the Planar cell polarity pathway important?
- shape the early embryo
- highly conserved
WITHOUT: neural folds remain far apart and neural tube closure is absent
