Question

You have constructed a new reporter gene to help you find novel zebrafish mutations. The reporter gene consists of several LEG/TCF binding domains in the enhancer fused to the coding region for green fluorescent protein (GFP). Wild-type embryos that contain this transgene normally express it in the brain and eye primordia and have no developmental defects.

You then mutagenize this reporter strain to look for new mutants that affect GFP expression. Which developmental pathway are these mutants likely to be in and why?

You find a mutant (which you call GLO-1) that ubiquitously expresses your reporter gene throughout the entire embryo. Which molecule in the above pathway is most likely to be mutated and why?

Answer 1

• In the process of isolation and identification the new mutation will get affect by the pigment cell fate in the "zebrafish neural crest."
• Homozygous nacre (nac(w2)) mutants will lack in the melanophores throughout their development but they possess an increased number of iridophores.
• In the "non-crest-derived," the retinal pigment epithelium is normal; hence the mutation will not affect the pigment synthesis.
• In the early expression of nacre mutation "melanoblast" markers are absent and they will transplant the cell-autonomous function in melanophores.
• Here we can find the nac(w2) mutation in a zebrafish gene".
• This gene will encode a basic "helix-loop-helix/leucine" zipper transcription factor that were associated with the microphthalmia (Mitf) gene that is required for the development of the pigment cells (eyes and crest) in the mouse.
• In the "transient expression," the "wild-type" nacre gene restores the melanophore development in nacre embryos.
• Nacre misexpression induce the formation of "ectopic" melanized cells will cause the defects in eye development (such as "wild-type" and "mutant" embryos.)
• To finalize the end product in the melanophore development (like fish and mammals).
• It will share the nacre/Mitf transcription factor that will help in the proper development of the fish retinal pigment epithelium it called as "not nacre-dependent."
• Hence these genes are involved in the evolutionary divergence.
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