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Dipl.-Biol. Jan Felix Evers

phone:   ++49 30/838-56443,-56880
fax:        ++49 30/838-55455
e-mail:   fevi@zedat.fu-berlin.de
personal homepage:

 

I use the motoneuron 5 (MN5) of Manduca sexta as a model system to study the mechanisms underlying structural changes in dendritic geometry during the postembryonic integration of central neurons into newly formed networks. During metamorphosis MN5 changes from a slow motoneuron innervating a larval crawl muscle to a fast flight motoneuron.  During this switch of the behavioural context, MN5 undergoes drastic dendritic regression during late larval life until pupal stage P2. Growth-cone dependent dendritic growth starts at P3 and lasts until stage P6. Subsequent dendritic growth is limited to higher order dendritic branching. Dendritic growth as well as growth-cone formation and collapse concomitantly occur with characteristic changes of postsynaptic potentials as measured in somatic recordings.

Activity dependent alterations of dendrite and growth-cone structure during postembryonic development

In this part of my PhD thesis I like to describe how activity is contributing to structural alteration and elimination of dendritic growth-cones. As growth-cones are the cell organs capable to in chemical gradients during outgrowth of both, axons and dendrites, without direct cell contact to their target partners, they may serve as initial pathfinder but collapse as soon as a certain amount of synaptic contact is established. This hypothesis implies activity to be a regulatory factor for growth-cone morphology. I already established a database of the morphologic key factors of ‘wild-type’ growth-cones. This will serve as a backbone to evaluate effects of manipulation of either synaptic or intrinsic neuronal activity.

Description of synaptogenesis applying high resolution confocal laser microscopy

Following synapse elimination during late larval life and crawling circuit dismantling, synaptogenesis apparently must take place when MN5 becomes integrated into the adult flight circuits. To understand more about places and dynamics of synaptogenesis, I try to perform triple labelling of MN5 and presynaptic and postsynaptic proteins at subsequent developmental stages and record with high resolution confocal laser microscopy. I developed a reconstruction module which incorporates into the commercially available software package Amira to evaluate the probability of synaptic contact. The sum of the fluorescent intensity of either pre- or postsynaptic marker is assigned to triangulated surface patches of a detailed reconstruction of MN5. This description will address the localization, distribution, and maintenance of synapses throughout an entire dendritic tree during postembryonic circuit development.

Reconstruction module for precise evaluation of neuronal arborization

A prerequisite to study the above described questions, it is essential to have precise reconstruction of neuronal arborization. As there was no tool automating the reconstruction process without partially sacrificing the precision of the result, it was essential to develop this during the first part my PhD. The work was started in 2003 together with Stephan Schmitt from the Technical University Berlin and is described in Schmitt et al., 2004 and Evers et al., 2004. The binary module integrates into Amira-3.1.1 and can be downloaded from this page below. For installation, unpack it into the Amira program root directory (in most cases C:\Programs\Amira-3.1.1).

I just started with versioning, and a new version is now online: 1.0

  Amira-3.1.1 VC6 Amira-3.1.1 VC7
windows version hxskeletonize_10_VC6.zip hxskeletonize_10_VC7.zip

 

If you need versions compiled for Linux or SGI Irix, please write an email to fevi@zedat.fu-berlin.de. A brief program documentation and user manual is provided below:

rekonstruktionManual.pdf

 

Selected Publications

Evers JF, Schmitt S, Sibila M, Duch C. Progress in functional neuroanatomy: precise automatic geometric reconstruction of neuronal morphology from confocal image stacks. J Neurophysiol. 2004 Nov 10

Schmitt S, Evers JF, Duch C, Scholz M, Obermayer K. New methods for the computer-assisted 3-D reconstruction of neurons from confocal image stacks. Neuroimage. 2004 Dec;23(4):1283-98.

 

 

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