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| Development of the Zebrafish Nervous System
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Participating
Scientists: M. Bastmeyer, J. Bentrop, M. Langhauser, K. Fazekas, O. Trapsch
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Axon guidance, the process by which neurons send out axons to reach their correct targets,
follows very precise paths. Our research projects aims at understanding the mechanisms involved
in axonal pathfinding and target recognition during nervous system development in vertebrates.
We study these processes in a simple and versatile model system, the zebrafish.
With regard to the regulation of axon navigation, we currently focuss on the role
of cell adhesion molecules of the NCAM-type (neural cell adhesion molecule)
and their very unique posttranslational modification by the glycan Polysialic Acid.
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.
(funded by the DFG)
I) 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)
II) In situ hybridization shows that sialyltransferase St8SiaIII is expressed in the
somites of the developing zebrafish (A) 24 phf old embryo (B) close-up
of (A).
(D) Morpholino-knockdown of St8SiaIII causes loosening of muscle fibrills (red)
and abnormal projection of axons innverating the somites (green). (C) wild-type.
(from Bentrop et al., 2008)
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| Cell Adhesion and Migration on Micropatterned Substrates
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Participating
Scientists: M. Bastmeyer, Z. Jiang, F. Klein, D. Lehnert
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Cell adhesion, the interaction of cells with each other or with the extracellular matrix
(ECM), is a complex process that plays a fundamental role during development of multicellular organisms.
To understand how cell behavior is dictated by the architecture of the ECM, we expose cells to patterned
substrates that consist of small ECM-coated dots in the submicrometer range separated by nonadhesive regions
in µm dimensions. These substrates are obtained by microcontact printing (µCP) and related techniques. Cell
reactions are analysed with confocal laserscanning microscopy after immunostaining or with videomicroscopy of
living cells that express different GFP-tagged proteins.
(funded by the CFN)
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| Axon Guidance by Substrate Bound Protein Gradients
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Participating
Scientists: M. Bastmeyer, R. Lattanzio, A. von Philipsborn
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Many axonal projections establish an orderly arrangement of connections within their target fields, termed a
topographic map. According to the chemoaffinity hypothesis, precise mapping in the vertebrate visual system
is guided by complementary gradients of Eph-receptors and ephrin-ligands. We use microfluidic networks and microcontact
printing techniques to produce various types of substrate bound ephrin-gradients. The behavior of retinal axons from fish,
frog and chick in different graded fields is then quantitatively analyzed and studied with timelapse microscopy. In
particular, we are interested how discontinuous or graded distributions of guidance molecules are computed within a
growth cone.
(funded by the DFG; in collaboration with Prof. F. Bonhoeffer and S. Lang, MPI Tübingen)
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