Zurück zur Übersicht "Forschung"
Scientists involved: Dr. Joachim Bentrop, Melanie Langhauser, Michaela Schober, Heinrich Schopf, Prof. Dr. Martin Bastmeyer
Funding: German Research Foundation (DFG)
In addition to axon guidance molecules, cell adhesion molecules (CAMs) play a major role during development
of the nervous system. The spatiotemporal expression of various CAMs and their modification with glycoepitopes
is involved in processes like neuronal cell migration, axonal pathfinding and target recognition. We study
these processes in a simple and versatile model system, the zebrafish. Our current projects focus on cell
adhesion molecules of the NCAM-type (neural cell adhesion molecule) and their modification by sialic acids.
This posttranslational modification is synthesized by a family of sialyltransferases which show a highly
regulated expression pattern during zebrafish development.
Besides studying gene expression patterns by in situ hybridization and immunochemistry, we apply a variety
of functional assays including morpholino antisense techniques, in vivo injection of antibodies as well as
transgenic expression of recombinant proteins, both, in the zebrafish and in cell culture studies. Analysis
of perturbation experiments includes whole-mount immunocytochemistry with confocal laserscanning microscopy
and live imaging in transgenic zebrafish lines that express green fluorescent protein (GFP) under various
neuron-specific promotors.
Project 1: Phylogeny and functional divergence of NCAM homologs
Whereas other vertebrates express two NCAM paralogs, namely NCAM and OCAM, teleost fishes have duplicated
the NCAM gene to yield NCAM and PCAM in addition to OCAM. To provide a molecular framework for understanding
the evolution of functions in this system, we combine phylogenetic analyses, gene expression studies and
functional examinations.
Project 2: Regulation and function of NCAM poly-Sialylation
Functional properties of NCAM paralogs are regulated by a unique glycan modification, namely the addition
of polySialic acid. polySialic acid is known to intricately influence the homophilic and heterophilic
interactions of NCAM with a multitude of cell surface and extracellular protein partners. To elucidate the
mechanisms affecting NCAM polySialylation, we study the distribution of NCAM paralogs with or without polySia
and the expression pattern and the enzymatic activities of enzymes of the polySia synthetic pathway.
Collaborating Scientists: Wiebke Schaper, Anja Münster-Kühnel, Rita Gerardy-Schahn
(Medizinische Hochschule Hannover)
Project 3: Evolution of the polySia/NCAM - System
Towards clarifiying the conservation and/or species-specific diversification of NCAM paralogs, NCAM modifying
enzymes and interactions partners, we extend our studies to farther related species, namely the Medaka model
organism. In silico analyses are complemented by examining the expression patterns and the function of relevant
proteins.
Collaborating Scientist: Felix Loosli (KIT)
Projection pattern of cranial nerves
of a 48 hpf zebrafish wholemount embryo stained with
antibodies against cell adhesion molecule zL1 (green) and polySia (red). A specific subpopulation of axons expresses
polySia (yellow = overlay of green and red staining).
A subpopulation of neurons is labelled by injection of a diffusible
dye (blue). (from Begemann et al., 2004)