Development and Evolution of the Arthropod head

All projects of the lab center on the development and evolution of the arthropod head and brain. Drosophila turns its head outside in during embryogenesis (head involution) which has hampered the genetic analysis of head and brain patterning in this species. Therefore we chose the red flour beetle Tribolium castaneum with its insect typical larval head as model system. Both the head epidermis and the neural stem cells arise in the same tissues at the same time. Therefore, we regard these two processes as two outcomes of the same early patterning events that should be studied together.

The developmental genetics of head development

Drosophila has turned out to be a poor model system for head development because of the reduction and involution of the larval head. Tribolium develops an insect typical larval head. We try to understand head development in this species by three complementary approaches: The candidate gene approach reveals what the players known from Drosophila do in Tribolium. In order to identify new players, we perform RNAi and transposon mutageneses. In vivo imaging lines have been established in the lab in order to understand the tissue and cell movements that lead to head formation.

The specification of neuroblast identity

Neuroblasts are neural stem cells that delaminate from the neuroectoderm and subsequently divide asymmetrically. Their daughter cells divide once more to build the neurons and glia cells of the brain. Importantly, neuroblasts develop cell autonomously once they have delaminated. Therefore, the signals that make them different from each other must have acted when they still reside in the neuroectoderm. While these signals are well described for the trunk ganglia, they are largely unknown for the brain. We want to identify these signals.

The arthropod head problem

The arthropod head is a composite structure of several segments and probably anterior non-segmental tissue (acron). It has remained debated, however, how many segments compose the insect head and if there is an acron at all. The genes that we identify in our screens are at the same time useful markers for answering the old questions with respect to the labrum, non-segmental tissue and the number of head segments. In collaboration with others we extend these results to other arthropod and protostome species.

© Gregor Bucher, last update: december 08