Pattern Formation, Antero-Posterior (AP) and Dorso-Ventral (DV) Axes Formation

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Preknowledge, Objectives and Competencies



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Preknowledge

  • Gastrulation in amphibia, mammals and birds (BIOSCI 107 and Unit 1)
  • Formation of the 3 germ layers and their derivatives (BIOSCI107 and Unit 1)
  • Development of the neural tube (BIOSCI 107 and MEDSCI 206 and Unit3)
  • Definitions of different processes of development (Unit 2)




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Objectives

In this unit we will build on prior knowledge to construct a detailed image of how the antero-posterior (AP) and dorso-ventral (DV) axes are specified. We will examine the roles that the embryonic mesoderm and the embryonic organisers play in this process. We will also examine how morphogens, and other signalling processes direct the differentiation of the nervous system. We will also examine how these processes differ in the spinal cord, hindbrain, mesencephalon and telencephalon.



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Competencies

At the end of this unit you should be able to:
  • Gain sufficient understanding of the processes that lead to the patterning of the different axes in the developing nervous system.
  • Gain sufficient understanding of the tissue and molecular interactions that guide these processes.
  • Gain sufficient understanding of the processes that determine the AP axis in order to extrapolate to the formation of the DV axis.
  • Be able to provide a description of the effects of different genes and molecules on the process of axis formation.
  • Be able to predict the developmental outcomes related to mutations or disturbances in the signalling processes.


Activities and Reading Material



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Activity
During class, we will look at the process by which the the AP axis is established. We will examine the role of morphogens and their gradients in establishing developmental axes. We will also examine the interaction of the neural plate and underlying mesoderm that determine the AP identity of different parts of the neural tube. We will use the knowledge gained to discuss the concepts of 'head' and 'trunk' and discuss the idea of segmentation in the spinal cord and hindbrain. We will use the tables provided in the lecture notes to summarise the origin and roles of different genes and molecules during the processes examined in lecture.




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Reading


  • Purves et al Chapter 22 (pp 547-562)
  • Jacobsen Chapter 4

Assignments



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Assignment

After class, you are expected to review your notes and use the assigned reading material to complete a descriptive table of the different genes and molecules involved in the AP and DV patterning of the nervous system. You are expected to contribute to the questions and definitions sections below. Please use the discussion page if you want to discuss any particular topic on the material. You are also welcome to add links to videos or audio files in the Media box or links to online resources in the Web Resources box below.


Questions



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Question

Would you consider the spinal cord to be a segmented structure? Explain your rationale.


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Question

Would you consider the forebrain to be a segmented structure? Explain your rationale.


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Question

What congenital defects would you expect to see following mutations of the genes covered in class?


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Question

Look up the synthetic pathway for retinoic acid. How would you expect diet/behaviour to affect the developmental processes covered in this Unit?


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Question

Can you find examples of medical conditions associated with deficiencies/mutations of any of the factors mentioned in this unit?


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Question

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Definitions


You should be able to provide structural and functional definitions for the structures associated with this topic: (Chordamesoderm, Prechordal mesoderm, Head Organizer, Tail Organizer, Isthmic Organizer, Spemann's Organizer, Rhombomeres, Anterior Visceral Ectoderm (AVE)).



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Definition
Chordamesoderm:



Enter your definition here



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Definition
Prechordal Mesoderm:



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Definition
Head Organizer:



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Definition
Tail Organizer:



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Definition
Isthmic Organizer:



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Definition
Spemann's Organizer:



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Definition
Rhombomeres:



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Definition
Anterior Visceral Ectoderm:



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Definition
Genes and molecules: Fill in the table.



Please visit the table in Unit 3 and fill in the new roles of genes/molecules discussed in this Unit.

Molecule/Gene Produced by/in Acts on Effect
SHH
Otx2
Hox
Retinoic Acid
GBx2
Mesx1

Additional study material



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Media


Add Links to media resources here



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Web Resources



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Related Content

Go back to the introductory page, return to Unit 3: Formation, Organization and Morphogenesis of the Neural Plate or continue with Unit 5: The Neural Crest.