Question

1. The release of BMP and Fgf8 from the optic vesicle to the overlying ectoderm-derived tissue results in the formation of the eye lens.

1. Identify and briefly explain this type of signaling phenomenon?

2. Why do some tissues respond to the above signaling and some tissues do not?

3. How would you test to see if a tissue is sufficient to affect another tissue type?

Answer 1

a. This type of signaling is known as paracrine signaling. Here, BMP and fgf8 are released by optic vesicles and BMP, fgf8 mediate cellular signaling in the overlying ectoderm-derived tissue. In presence of BMP and fgf8, the overlying ectoderm-derived tissue is converted into eye lens. BMP and fgf8 are two signaling factors, produced at one place and move to another place via diffusion and start cellular signaling in another place - this is the same feature which is used by factors that mediate paracrine signaling.

b. Some tissues respond to this signaling because they posses the corresponding cell surface or cytoplasmic receptors. Some tissues which don't respond to this signaling don't posses any receptor of these paracrine factors.

c. To test to see if a tissue is sufficient to affect another tissue type, I have to do co-culcure with two different cell types from two different tissues and have to monitor the changes associated (in terms of morphological or molecular or transcriptional) with the two cell types. I also have to set up control sets, where only single cell type is cultured. I also do some extra modification in the co-culcure system by adding antibodies against the signaling factors or against the receptors. This will prohibite the signaling and will cause no change in the cell types.