Morphogens

Question 1

What is a morphogen?

Answer 1

-A morphogen is a diffusible molecule that triggers different cell fates at different concentrations

Question 2

What information do morphogens provide?

Answer 2

-Morphogens can provide positional information within the embryo

Question 3

What are morphogens secreted by?

Answer 3

Morphogens are secreted by discrete groups of cells in developing embryos called signalling centres

Question 4

What is an example of a morphogen wichih isn’t a secreted molecule?

Answer 4

-An example is Bicoid during the patterning of the anterior and posterior axis of the drosophila embryo.

Question 5

What is Bicoid?

Answer 5

-A transcription factor found in the nucleus

Question 6

Bicoid in drosophila embryo

Answer 6

• Many cycle of mitosis lead to generation of many nuclei
• Bicoid mRNA is deposited in the egg maternally whilst the egg is being formed
  
  • Is concentrated at one end of the embryo
• As Bicoid mRNA is translated into protein, the protein diffuses through the embryo
  
  • This generates a concentration gradient
    - This leads to activation of transcription genes in different position of the embryo.

Question 7

What are the molecular mechanisms downstream of morphogens?

Answer 7

• Receptor tyrosine kinases(RTKs) family: PDGF, EGF, FGF, VEGF
• Transforming growth factor beta superfamily: TGF, BMPs, activin
• Hedgehog
• Wnts