Prof. Dr. Jean-Marc Fritschy

 

Main Goals, Keywords

• Analysis of the molecular and cellular organization of GABAergic neurotransmission in normal and diseased brain using high-resolution microscopy
• Elucidation of the molecular mechanisms of GABAergic synapse formation and plasticity, with a focus on the regulation of gephyrin, the main scaffolding protein of inhibitory synapses in the CNS
• Role of the GABAergic system in the regulation of adult neurogenesis in the hippocampal formation and olfactory bulb
• Investigating the pathophysiology of epilepsy (kainate mouse model of temporal lobe epilepsy), in particular the role of neuro-immune interactions in epileptogenesis and neurodegeneration

Keywords: synapse formation and plasticity; inhibitory neurotransmission; GABA_A
receptors; mutant mice; adult neurogenesis; epilepsy; seizures; inflammation

Group Members

2 postdocs, 3 PhD students, 1 MD/PhD student, 2 technicians

Previous and Current Research

The major topic of research is the functional organization and plasticity of the GABAergic system, using a multidisciplinary approach ranging from molecular and cell biology to immunoelectron microscopy. In vitro experiments in primary neuronal cultures transfected with plasmids of interest provide a powerful tool to study the molecular mechanisms of synapse formation and plasticity. Our main working hypothesis is that the postsynaptic scaffold formed by gephyrin is a hub integrating multiple signaling cascades to regulate GABA_A receptor function and to mediate cross-talk with excitatory synapses. In addition, transgenic mice expressing reported genes in neurons of interest, as well as mutant mice with targeted gene deletions affecting the GABAergic system, are essential to our in vivo experiments and our morphological studies using light and electron microscopy.

As part of the NCCR-Neuro project 1 (Stem cells) our group contributes to a research project aiming at unraveling the role of GABAergic transmission in the regulation of adult neurogenesis. This work is conducted in mice lacking specific GABAA receptor subtypes and uses retro- and lentiviruses for transfecting newborn cells, followed by morphological and functional analysis.

A better understanding of the structure and function of the healthy brain is a major prerequisite for studying the pathophysiology of neurological and psychiatric disorders. Animal models are essential for elucidating cellular and molecular alterations that might contribute to the etiology of brain disorders. To fulfill this aim, we are working with a mouse model of temporal lobe epilepsy that mimics three main aspects of the disease: pattern of neuronal loss and astrogliosis, occurrence of spontaneous recurrent partial seizures, and activation of innate and acquired immunity. Our current focus is the role of acquired and innate immune responses in epileptogenesis and occurrence of recurrent seizures.

Research Projects

 1. GABAergic synapses and circuits

• Role of GABA_A receptor for the formation and maintenance of GABAergic synapses, analyzed in mutant mice lacking specific GABA_A receptor subunits
• Regulation of GABA_A receptor cell-surface targeting and synaptic clustering
• Molecular mechanisms and signaling cascades regulating the gephyrin postsynaptic scaffold in GABAergic synapses

2. Role of the GABAergic system in the regulation of adult neurogenesis

• Perturbation of adult neurogenesis in mutant mice lacking specific GABA_A receptor subunit: differential role of tonic and phasic inhibition on neuronal proliferation, migration, and differentiation
• Role of GABA_A receptors for synaptic integration of newborn olfactory bulb granule cells

3. Pathophysiology of epilepsy

• Mechanisms of epileptogenesis in a mouse model of focal hippocampal seizures, with a focus on neurotrophin signaling
• Role of neuro-immune interactions for neurodegeneration, epileptogenesis, and onset of recurrent seizures
• Molecular and cellular mechanisms contributing to dentate gyrus granule cell survival and dispersion in temporal lobe epilepsy
• Alterations in neurotransmitter circuits and receptor expression in human epilepsy: analysis of tissue resected at surgery

4. Methodological developments

• Antigen-retrieval immunohistological methods for improved detection of membrane proteins
• Live-imaging of synapse formation and regulation, as well as receptor trafficking in cultured neurons (time-lapse microscopy, FRAP, FRET)
• High-resolution immunofluorescence microscopy based on post-hoc image restoration (deconvolution)
• Pre- and post-embedding immunoelectron microscopy

Techniques and Equipment

Immunohistochemistry: single and multiple labeling studies in tissue sections and cell cultures; immunoelectron microscopy; in situ hybridization histochemistry

Molecular Biology; protein biochemistry; primary neuron culture and transfection by magnetofection

Stereotaxic surgery, intracerebral virus injection, EEG recording

Microscopy and imaging: Confocal laser scanning microscopy and epifluorescence microscopy; live-imaging of cultured neurons; computer-based image analysis and densitometry

Main equipment: Zeiss LSM 710 Zen and LSM 510 Meta confocal laser scanning microscopes; Zeiss Apotome; Leica inverse microscope for live-cell microscopy; image analysis systems (MCID, ImageJ, Imaris); standard equipment for molecular biology, biochemistry, histology and autoradiography, cryostat, microtome, cell culture facilities.

All major protocols used in our laboratory can be downloaded from our website (see link below)

Selected Publications

• Tyagarajan SK, Ghosh H, Yévenes GE, Imanishi SY, Zeilhofer HU, Gerrits B, Fritschy JM. Extracellular Signal-regulated Kinase and Glycogen Synthase Kinase 3β Regulate Gephyrin Postsynaptic Aggregation and GABAergic Synaptic Function in a Calpain-dependent Mechanism. J Biol Chem. 2013 Apr 5;288(14):9634-47. doi: 10.1074/jbc.M112.442616. Epub 2013 Feb 13.
• Fritschy JM, Sarter M. Early brain repair and protection. Eur J Neurosci. 2012 Jun;35(12):1810. doi: 10.1111/j.1460-9568.2012.08173.x.
• Marowsky A., Rudolph U., Fritschy J.-M., and Arand M. Tonic inhibition in the basolateral amygdala is mediated by a3 subunit-containing GABA_A receptors. J. Neurosci. 32, 611-619 (2012).
  
• Paul J., Zeilhofer H.U., and Fritschy J.-M. Selective distribution of GABA_A receptor subtypes in mouse spinal dorsal horn neurons and primary afferents. J. Comp. Neurol., April 23, epub ahead of print (2012).
  

Selected Lectures, Seminars, Colloquia

• Pharmakologie und Toxikologie für Studierende der Medizin, Zahnmedizin, und Biologie
• Human Biology Modules BIO402 and BIO422 (Cellular and System Neuroscience)
• Introductory and Advanced Course in Neuroscience of the ZNZ
• Seminar series in Pharmacology and Toxicology

Funding

Swiss National Science Foundation, NCCR-Neuro, Hartmann-Müller Foundation, Swiss League against Epilepsy

URL

http://www.pharma.uzh.ch/research/neuromorphology/researchareas/neuromorphology.html