Speaker
Description
Evolutionary adaptations of brain structure and function are essential for animal survival and emerge during development. Some known divergences seen in brain development are likely relevant for brain function. For instance, adult neurogenesis in mushroom bodies is found in beetles but not in flies and might modify learning behavior. Further, beetle larvae have a partial central complex (CX) while fly larvae lack a visible CX. However, the cellular and genetic mechanisms controlling diversification remain enigmatic.
To study brain diversification both, between life stages and between taxa, we used homology-directed genome editing to transgenically mark homologous cell groups throughout development. Specifically, we marked all cells expressing the transcription factor retinal homeobox (rx) in the fly Drosophila melanogaster and the beetle Tribolium castaneum. These genetic neural lineages are precise tools to mark and compare the development of homologous neural cells from the embryo to the adult.
So far, we found several differences between fly and beetle: Nine type II neuroblasts are present in beetle embryos (compared to eight found in flies and grasshoppers), which show an increased division activity. This correlates with the earlier emergence of a central complex in beetle larvae. In the adult brain, we found a cell cluster in flies, which seems to be absent in beetles. Finally, a change of rx expression in the mushroom bodies likely correlates with differences in adult neurogenesis between fly and beetle.
We will follow up these differences to reveal the underlying genetic and cellular mechanisms.
