To understand how the notochord controls morphogenesis in the mesencephalon, I have undertaken a study to fully characterize the microsurgical manipulation that perturbs development. I have discovered that the same phenotype can be achieved by merely separating, rather than removing, the notochord from the overlying neural tube and that this effect is stage- and regional-specific. It is known that the development of the mesencephalon is regulated by an organizing centre situated at the metencephalic boundary, referred to here as the MHB. I have addressed the contribution of the MHB, neutral tube and notochord towards the phenotype by analyzing the expression patterns of a variety of developmental control genes after the manipulation. In the MHB, <I>Wnt1, En1 </I>expression are initially reduced after the manipulation, and <I>Wnt1</I> recovers to control levels by 48 hours; no change is seen in <I>Fgf8</I> expression. The presence of notochord and floor plate was also assessed by the expression of Sonic hedgehog (SHH). Interestingly, while Stage 11 embryos maintained expression of <I>Shh</I> in both structures, Stage 12 embryos lost notochord expression after 24 hours and showed a reduced floor plate expression after 48 hours. This correlates with the stage specificity seen for the manipulation. These results provide an <I>in vivo</I> model to study the consequences of a conditional loss of notochord signalling after axial patterning. To examine the response of later embryos, a histological analysis was performed and revealed a reduction in neutral tissue and ventricular space.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:596923 |
| Date | January 2000 |
| Creators | Britto, J. |
| Publisher | University of Cambridge |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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