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Prof. Ulrich Technau - Department Head

Most extant animal lineages belong to the Bilateria, which have two body axes (anterior-posterior or head-tail and dorso-ventral or back-belly). They are also composed of three germ layers, ectoderm, endoderm and mesoderm, which are laid down early in development and of which all tissues and organs differentiate. Furthermore, most bilaterians are characterized by a central nervous system, e.g. brain, nerve cord and ganglia. Differentiation from stem cells assures the maintenance of neurons throughout the life of the organism.

Our model organisms to study the evolution of these fundamental body plan features are the Cnidaria (sea anemones, corals, jellyfish, hydras), which are considered to be the sister group of the Bilateria. The Cnidaria are thought to have arisen some 600 Mio years ago. They display one apparent body axis (oral-aboral), and consist of only two cell layers, called ectoderm and endoderm. They have a diffuse nervous system.

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In many Drosophila species, autosomes have fused to the ancestral sex chromosome pair very recently which then evolve exactly like sex chromosomes. These particular so-called ’neo-sex’ systems are unique models to study fundamental questions like how X and Y chromosomes change their sequence feature and expression level during their divergence from each other, how are the processes dictated by chromosome-wide epigenetic regulatory changes, how dosage compensation evolves etc. These questions are usually very difficult to address in the classic model systems like human and Drosophila melanogaster, whose sex chromosomes are too old to study.

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We study major transitions in metazoan evolution from the perspective of the underlying genomic changes. Over the past years, we have contributed to the broader sampling of metazoan genomes, revealing ancestral metazoan and bilaterian genomic architectures and their diversification patterns. While we can trace back many gene families to the ancient metazoan ancestor, we also find many of them linked at both micro- (local gene cluster) and macro-syntenic (chromosomal) levels. The functional significance of most of those linkages during development is unknown. Having a broad phylogenetic focus we aim to (1) characterize and expand our knowledge of conserved and novel gene linkages and their associated (non-coding) elements across metazoans, (2) study their evolutionary dynamics through comparative genomics and modeling approaches, and (3) establishing molecular tools for investigating their role during development and clade-specific innovation.

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I am interested in understanding how molecular mechanisms regulating animal body axes evolved. To find this out, I am using an excellent experimental model, the sea anemone Nematostella vectensis. It belongs to Cnidaria, a phylum consisting of morphologically simply organized diploblastic organisms, which occupies a crucial phylogenetic position as a sister group to all Bilateria (triploblastic animals with anterior-posterior and dorsal-ventral body axes).  Intriguingly, true bilaterality exists also outside Bilateria, and Nematostella is one of such non-bilaterian bilaterally symmetric animals.