Question

1. Morphogens in development are signaling molecules that emanate from a restricted region of a tissue and spread away from their source to form a concentration gradient. They act on cells directly to induce distinct cellular responses, such as inducing neural plate formation. In a recent transcriptome screen, a newly discovered gene, called Not Really a Gene (NRG) was found to be expressed just prior to neural plate induction in chicks. In situ hybridization confirmed that the NRG gene is turned on in the underlying mesoderm at that time.
   1. From the data above, can you conclude whether NRG is really a morphogen? Why or why not?
   2. Your professor tells you that he needs some preliminary data because he is submitting a grant on NRG and early morphogen activity. Describe at least two experiments you can run that will give definitive evidence that support NRG as a morphogen in early neural induction. In other words, what are some experiments that show NRG acts in a concentration dependent manner and act directly on cells to induce a neural fate?

Answer 1

a. NRG is not a morphogen but resembles morphogen activity. Morphogens are different from NRG because NRG were created to induce cell to cell signalling where as Morphogens are used in development of signaling molecules.

b.examples include the following:

1. Dorsalization of mesoderm and neural induction by spemann's organizer during gastrulation.

In this experiment the dorsal lip of blastopore transplanted to opposite side of the embryo,it enables host cells organizing them to form secondary body axis which contains many histotypes and complex structures. The small region of gastrula is used for isolating of new molecules for cell signaling. Synthetic mRNA were injected into ventral side of the embryo and single gene is identified.

2. Head induction method : Dickkopf

150 synthetic mRNA's were injected in truncated BMP receptor. The new gene was expressed in prechordal mesoderm and induced large heads or complete axes (trunk+ head).