Organizing the early spider embryo – Molecular and morphogenetic analysis of body axes formation in the spider Parasteatoda tepidariorum

• Applicant: Dr. Matthias Pechmann
• Subject Area: Evolutionary Cell and Developmental Biology (Zoology)
• Term: from 2019 to 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 422268363

The second most species rich group of animals on this planet are the chelicerates, which include horseshoe crabs, sea spiders and arachnids (e.g. spiders and scorpions). In chelicerates, the first body axis to be established is the anteroposterior axis. This process leads to the formation of a disc shaped embryo, termed the germ disc. Following this event, the dorsoventral body axis is established by a specialized group of cells, termed the cumulus, which functions as an organizing centre to break the radial symmetry of the germ disc. As has been shown with vertebrate organizers (such as the Spemann organizer in frogs), transplantation of the cumulus in chelicerate embryos can induce a secondary axis. Furthermore, both the vertebrate organizer and the chelicerate cumulus act via the same signalling pathway (namely BMP signalling). Axis patterning has been most extensively studied in the common house spider Parasteatoda tepidariorum, which is the best-established chelicerate model system for studying embryonic development. However, several important questions still remain open. First, what is the signal that establishes the anterior-posterior body axis of spider embryos? Second, how and when is the cumulus forming? Finally, which molecular factors are involved in this process? We will study the molecular and morphogenetic processes underlying axis determination and cumulus establishment in P. tepidariorum using various cell labelling techniques, live imaging, next generation sequencing, gene knockdown and gene overexpression experiments. The results of this proposal will help to better understand and compare axis determination and morphogenesis in animals.

• DFG Programme: Research Grants