Advisor: Andreas Wanninger

Master's Defensio - Friday, June 19th 2026, 9:00
SR 4.1, UBB, Djerassiplatz 1, 1030 Vienna 

Abstract

Segment polarity genes are well known for their role in segmentation; however, they are also widely expressed in diverse organ systems during animal development (e.g., engrailed expression in ectodermal boundaries in lophotrochozoans or during brain regionalization in chordates). Comparative studies across bilaterians have revealed a mosaic of conserved and clade-specific expression domains for these genes (e.g.   engrailed expression in delimiting shell fields in all mollusks and cephalopod-specific expression in limb development). To expand the comparative dataset for mollusks, the expression of engrailed, wingless, hedgehog, and even skipped were investigated during development of the polyplacophoran Acanthochitona fascicularis using whole-mount in situ hybridization.  Engrailed is expressed in cells surrounding the shell plates, in the posterior region of both nerve cords, and in the protonephridia.  Wingless expression is in the posterior ectoderm and in the radula sac.  Hedgehog is exclusively expressed in the anterior portion of the digestive tract (pharynx and radula sac).   Even skipped is expressed in mesodermal and ectodermal cells of the gastrula, in neurons of the pedal nerve cord, and in the plate fields. Compared to data on other lophotrochozoans, these results suggest independent recruitment of engrailed in neurogenesis and nephridiogenesis as well as a loss of hedgehog expression in myogenesis in polyplacophorans. Overall, segment polarity genes in mollusks exhibit a pattern of conserved expression domains and considerable gene plasticity.