Department for Cell and Molecular Biology
Wnt signaling in Zebrafish
Wnt-signalling is involved in a variety of processes, which include the emergence of diseases like cancer as well as early embryonic development.
We are particularly interested in the development of the vertebrate brain and we are using the zebrafish (Danio rerio) as our model organism to study the genetic pathways, which underlie its development. The vertebrate brain is an immensely complex structure, which exhibits numerous asymmetries, both morphological and functional. How these asymmetries are genetically established has remained a key open question, but failure in their proper development in humans can have devastating consequences like schizophrenia or depression.
Wnt and neural development
At least two structures in the zebrafish forebrain located in the dorsal diencephalon exhibit asymmetric features: The pineal complex and the habenulae. The habenulae connect fore- and ventral midbrain and are formed by a bilateral set of nuclei that are more pronounced on the left side in many vertebrates. The pineal complex consists of the more caudally located pineal and the left sided parapineal organ, which shows an asymmetric ipsilateral fiber projection towards the left habenula. Efferent projections from both habenulae innervate the interpeduncular nucleus in the ventral midbrain. The laterotopic segregation of these projections results in the transformation of the left right asymmetry in the dorsal diencephalon into a dorsal ventral asymmetry in the midbrain.
We could recently show that the Axin1 gene, which is a known inhibitor of the Wnt/b-catenin signalling pathway, is crucially involved in the establishment of brain asymmetries. We are combining molecular biology, genetics and advanced imaging to elucidate where, when and how Axin1/Wnt/b-catenin signalling contributes to the establishment of brain asymmetries. Our main tools are the analysis of zebrafish mutated in genes known to act in this pathway. Furthermore timely and spatially regulated misexpression of genes in combinations of wild type, mutant and transgenic animals complement our studies. Furthermore we are investigating new genes of the Wnt pathway and their potential role in the establishment of brain asymmetries.
Wnt and axis formation
Within the past 350 million years about 25.000 fish species have emerged. This makes fish the most diverse group of animals amongst all vertebrates. The two fish species mainly used in the laboratory are the zebrafish (danio rerio) and the medakafish (oryzias latipes), which are only distantly related. This provides us with the unique opportunity to perform comparative studies in morphologically similar species that are essential if we are to understand the conserved and species specific mechanisms that underlie vertebrate development.
One commonly used method to identify genes which play essential roles during embryonic development is to introduce random mutations into the fish genome. The resulting morphological alterations will then be analysed and the gene affected isolated subsequently. These mutagenesis screens have been frequently and successfully used in the zebrafish. In medaka, a number of mutants have been isolated in recent screens, which show unique phenotypes, which have not been found in any other vertebrate.
We are particularly interested in a group of mutants, which do not develop any trunk- or tail structures, while the head forms apparently normal.
In a collaborative effort one of these mutants has been isolated recently in the group of Hiroyuki Takeda. In this mutant a point mutation in the FGF-receptor1 causes the lack of trunk and tail structures. In contrast, the loss of FGF-receptor1 function in zebrafish causes the loss of a small area in the brain. These phenotypes are consistent with the different regions of FGF-receptor1 gene expression in medaka and zebrafish. This is a nice example of evolutionary divergence in the requirement of a specific receptor, most likely due to differential spatially regulated expression in the two species.
Currently we are analysing four other mutants using genetic, molecular and imaging techniques to identify the nature of the genes responsible for the lack of posterior embryonic structures and to understand the exact function of these genes during embryonic development in medaka. Subsequently, we will knock down the function of the zebrafish homologe and compare the function in these two evolutionary distantly related vertebrate species. We have already identified the gene affected in one of the mutants as being involved in the Wnt/b-catenin signalling cascade. This comparative approach will allow us to discriminate between species specific and conserved function of potentially new genes involved in posterior axis formation in vertebrates.
Interested scientists at any level can apply. Salary costs have to be raised beforehand (fellowships etc.).
Dr. Matthias Carl, Group leader
Luca Guglielmi, Ph.D. Student
Sara Asgharpour, Ph.D. Student
Former Group Members:
Nesrin Mwafi, Ph.D. Student
Alessio Paolini, Ph.D. Student
Tillmann Rusch, Practical Student
Aysu Kök, Practical Student
Raquel Jacinto, Ph.D. Student
Krystyna Zawieja, Technician
Carlo Beretta, Ph.D. Student
Ulrike Hüsken, Ph.D. Student
Kirsten Seufert, Fish Facility Assistant
Christian Altbürger, Practical Student
Elke von Ochsenstein, Technician
Shiqi Zhang, Practical Student
Christina Keiner, Internship Student
Ann-Christin Mentzer, Internship Student
Jacquline Siu, Internship Student
Griffin Hartmann, Practical Student
Natalja Mamaeva, Practical Student
Irena Brinkmann, Master Student
Hüsken, U., Stickney, H.L., Gestri, G., Bianco, I.H., Faro, A., Young, R.M., Roussigne, M., Hawkins, T.A., Beretta, C.A., Brinkmann, I., Paolini A., Jacinto, R., Albadri, S., Dreosti, E., Tsalavouta, M., Schwarz, Q., Cavodeassi, F., Barth, A.K., Wen, L., Zhang, B., Blader, P., Yaksi, E., Poggi, L., Zigman, M., Lin, S., Wilson, S.W., and Carl, M. (2014). Tcf7l2 is required for left-right asymmetric differentiation of habenular neurons. Current Biology 24(19):2217-2227.
Dross, N., Beretta, C.A., Bankhead, P., Carl, M., and Engel, U. (2014). Zebrafish Brain Development Monitored by Long-Term in Vivo Microscopy: A Comparison Between Laser Scanning Confocal and 2-Photon Microscopy. Book chapter in: Laser Scanning Microscopy and Quantitative Image Analysis of Neuronal Tissue, Springer Science.
Dreosti, E., Llopis, N.V., Carl, M., Yaksi E., Wilson, S.W. (2014). Left/right asymmetry is required for the habenulae to respond to both visual and olfactory stimuli. Current Biology 24(4):440-5.
Mwafi, N., Beretta, C.A., Paolini, A., Carl, M. (2014). Divergent Wnt8a gene expression in teleosts. Plos One 9(1):e85303.
Beretta, C.A., Dross, N., Bankhead, P., Carl, M. (2013). The ventral habenulae in zebrafish develop in prosomere 2 dependent on Tcf7l2 function. Neural Development 8:19.
Demir, K., Kirsch, N., Beretta, C.A., Erdmann, G., Ingelfinger, D., Moro, E., Argenton, F., Carl, M., Niehrs, C, Boutros, M. (2013). RAB8B is required for activity and caveolar endocytosis of LRP6. Cell Reports 4:1224-34.
Hüsken, U., Carl, M. (2013). The Wnt/beta-catenin signaling pathway establishes neuroanatomical asymmetries and their laterality. Mechanisms of Development 130: 330-335.
McNabb, A., Scott, K., von Ochsenstein, E., Seufert, K., Carl, M. (2012). Donít be afraid to set up your fish facility. Zebrafish 9:120-5.
Beretta, C.A., Dross, N., Gutierrez-Triana, J.A., Ryu, S., Carl, M. (2012). Habenula circuit development: past, present and future. Frontiers in Neuroscience 6:51.
Berns, N., Woichansky, I., Kraft, N., Hüsken, U., Carl, M., Riechmann, V. (2012). “Vacuum-assisted staining”: a simple and efficient method for screening in Drosophila. Development Genes and Evolution 222:113-118.
Beretta, C.A., Brinkmann, I., Carl, M. (2011). All four zebrafish Wnt7 genes are expressed during early brain development. Gene Expression Patterns 11, 277-284.
Wilkinson, C.J., Carl, M. and Harris, W.A. (2009). Cep70 and Cep131 contribute to ciliogenesis in zebrafish embryos. BMC Cell Biology 10:17.
Bianco, I.H., Carl, M., Russell, C., Clark, J. and Wilson, S.W. (2008). Brain asymmetry is encoded at the level of axon terminal morphology. Neural Development 3:9.
Carl, M., Bianco, I.H., Bajoghli, B., Aghaallaei, N., Czerny, T., and Wilson, S.W. (2007). Wnt/Axin1/b-catenin signalling regulates asymmetric nodal activation, elaboration, and concordance of CNS asymmetries. Neuron 55: 393-405.
Yokoi, H., Shimada, A., Carl, M., Takashima, S., Kobayashi, D., Narita, T., Jindo, T., Kimura, T., Kitagawa, T., Kage, T., Sawada, A., Naruse, K., Asakawa, S., Shimizu, N., Mitani, H., Shima, A., Tsutsumi, M., Hori, H., Wittbrodt, J., Saga, Y., Ishikawa, Y., Araki, K., and Takeda, H. (2007). Mutant analyses reveal different functions of fgfr1 in medaka and zebrafish despite conserved ligand-receptor relationships. Dev. Biol. 304: 326-337.
Francesco Argenton, University Padova, Italy
Patrick Blader and Myriam Roussigne, Université de Toulouse, France
Michael Boutros, DKFZ, Heidelberg, Germany
Filippo Del Bene, Curie Institute, Paris, France
Ulrike Engel, Nikon Imaging Center Heidelberg, Germany
Marika Kapsimali, Ecole Normale Superieure Paris, France
Cheol-Hee Kim, Korea
Suat ÷zbek, Heidelberg University, Germany
Soojin Ryu, MPI Heidelberg, Germany
Veit Riechmann, Heidelberg University, Germany
Sven Sauer, Heidelberg University, Germany
Steffen Scholpp, KIT, Karlsruhe
Christian Schultz, Heidelberg University, Germany
Herbert Steinbeisser laboratory, Heidelberg University, Germany
Rolf-Detlef Treede, Heidelberg University, Germany
Steve Wilson, UCL London, UK
Jochen Wittbrodt, Heidelberg University, Germany