Patterning The Brain Flashcards
What are the 3 primary brain vesicles?
Prosencephalon, mesencephalon and rhombencephalon
5 secondary brain vesicles?
Telencephalon, diencephalon, mesencephalon, metencephalon and myelencephalon
What signals pattern the AP/DV axes in development?
Wnt, BMP, FGF and retinoic acid
What signals pattern spinal cord?
Formed from ventral ectoderm. Fgf signals induce this as neuroectoderm. BMPs promote development into posterior neural tissue
What’s promotes neural and anterior identity?
BMP antagonists
What does lower gradient of Wnt do?
Anterior identity
Posterior specification?
High retenoic acid expressed in posterior, repress anterior HOX genes and express posterior HOX genes
Regions of brain?
Otx2+Six3
Otx2+Irx3
Gbx2+Irx3
Forebrain
Midbrain
Hindbrain
What boundary area represents the border between Otx2 and Gbx2?
Isthmic organiser (midbrain/hindbrain boundary=MHB)
What does isthmus (MHB) do?
Required to pattern both cerebellum and midbrain. Expresses FGF8 to form midbrain and cerebellum. Expresses Wnt1 to form midbrain.
What does Anterior Neural Border (ANB) do?
Required for forebrain patterning. ANB secretes Wnt antagonist (SFRP and tlc)
How is the hindbrain segmented?
Rhombomeres are cell tight compartments within which neural precursors acquire positional identity. Rhombomeres defined by HOX expression. Diff HOX for diff rhombomeres boundaries. E.g. Hoxb1 required for r4.
What does notochord do?
Organiser of ventral spinal cord. Induces floor plate and motor neurons in SC.
Diff in signals of neural roof plate and floor plate?
Roof plate secretes BMP causing cascade of gene expression (TGF beta). Floor plate (and notochord) secretes sonic hedgehog dorsally. Neural identity determined by combination of concentrations of these molecules. Induce diff transcriptions factors.
Bonus: shh represses class 1, activates class 2. Cross repressive interactions determine progenitor domain boundary. Controls neuronal fate.
