Evolution of pigment patterning in Danio fish

Advisor: Uwe Irion

Location: Max Planck Institute for Biology Tübingen

Pigment patterns are very conspicuous features of many animals. They serve a variety of different functions and are of great evolutionary significance, as direct targets of natural and sexual selection. Zebrafish, Danio rerio, which are widely used as model organisms in bio-medical research, show an invariant and conspicuous pattern of horizontal dark and light stripes on the flank and in the anal and tail fins. The pattern is generated in the skin of the fish by three different types of pigment cells, dark melanophores, orange xanthophores and silvery or blue iridophores. Over the years a number of mutants have been collected that show aberrations in the stripe pattern. Several of the affected genes in these mutants encode membrane proteins, which are thought to be directly responsible for the patterning via cell-cell interactions. Other Danio-species, which are closely related to zebrafish, show an even wider variety of different patterns; they range from stripes to different spots or bars. However, in all these species the different pigment patterns are generated by the same types of pigment cells. Therefore, this species group is an attractive model to study the evolution of pigment pattern formation in vertebrates. We have established breeding colonies for a number of these different Danio-species in the laboratory and are now beginning to use them for experiments, including gene knock out with the CRISPR/Cas-System, generation of inter-species hybrids and chimeras. This allows us to identify differences and commonalities in the mechanisms that lead to the generation of the different patterns. The project will be based on inter-species complementation tests in hybrid fish in combination with functional tests of candidate genes in several species. We can use the CRISPR/Cas system to address the question whether changes in coding sequences or in cis-regulatory regions are evolutionary relevant, and thus learn about the origins of biodiversity in this group of fish.

 

More information about the research of Uwe Irion and a selection of recent publications can be found on his faculty page.

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