Lecture 9 Flashcards
Describe neural induction
The organiser cells that intrinsically expresse gsc and siamois begin to express chordin, noggin, folistatin and frizbee which prevent BMP4 from binding to receptors, inducing neural identity
Describe an experiment to prove that the organiser secretes signals that induce neural identity
Ectopically graft the dorsal lip (organiser) and it induces a second archenteron which have been induced by the second organiser
What is induction?
Change in cell fate mediated by extrinsic signals
How does the A/P axis form
The organiser self differentiates into the anterior endoderm, prechordal mesoderm and the notochord which forms a rod under the midline of the neural plate. It undergoes convergent extension movements which drives elongation of the neural plate and its transition into the neural tube by folding laterally to medially.
How does the neural tube acquire A/P identity?
The anterior endoderm and prechordal mesoderm are the first to differentiate and upregulate BMP antagonists to the anterior neural plate which induces forebrain identity- they are also exposed to Wnt antagonists. The notochord induces proliferation, FGF, RA and Wnt which induces posteriorizing factors and inhibits anterior properties
How are different domains of the hind brain and spinal cord defined?
Through HOX gene signature which is induced by RA gradient- they are often expressed redundantly (overlap). Interactions between the hindbrain and forebrain induced the midbrain.
How is dorsal identity induced in the neural tube?
BM7 from the roof plate extrinsically acts on dorsal neural tube cells to upregulate Wnts1, msx and BMP6 which activates lim1, PAX6/7/3 to induce dorsal identity
How is ventral neural tube identity induced?
Shh is produced by the notochord and the floor plate which sets up a Gli activator and repressor gradient which turns on different homeodomain TFs- which dictates later transcription
