ayout 1 - EMBL Grenoble

EMBL Research at a Glance 2009
Signalling mechanisms and gene regulation in
the nervous system
Liliana
Minichiello
PhD, University of Naples,
Italy, and The National
Cancer Institute, NIH,
Bethesda, (MD), USA.
Postdoctoral work at EMBL
Heidelberg 1993/99.
At EMBL Monterotondo since
2000.
Visiting Professor, Stem Cell
Center, University of Lund,
Sweden since 2005.
Previous and current research
Studying signal transduction in the mouse nervous system is the main focus of the group. In particular,
one major question is to understand the molecular mechanisms of learning. To address this
question we are using different approaches. To determine whether the molecular pathways required
for learning are also those generating long-term potentiation (LTP, considered to be the
mechanism for acquisition and storage of information by synapses in the brain) when measured
directly on the relevant circuit of a learning animal, we have employed a novel combination of in
vivo methods combined with highly defined genetic mouse models, which allow us to interfere
with single phosphorylation sites on a large receptor protein. Thus, we have been able to show
that signalling through the TrkB receptor and its PLCγ docking-site is important for associative
learning and parallel LTP (see figure), indicating that the same molecular mechanism forms the
basis for learning a task and for changes in synaptic plasticity seen during LTP in awake animals.
Future projects and goals
We have now begun to address molecular mechanisms by which TrkB receptor regulates synaptic
function by using in vivo cell specific proteomics. We would like to underpin specific signalling
complexes formed downstream of the TrkB receptor. The methods we are employing include the
co-precipitation/mass spectrometry approach combined with the TAP-tag strategy, in which a
tandem affinity purification tag is inserted into the mouse gene of interest by homologous recombination
in ES cells.
Critical to brain function is the balance between inhibition and excitation.
Thus, to determine functional and/or morphological feature of
inhibitory interneurons, current areas of interest include selective
knockouts of key molecules expressed in inhibitory interneurons. As
the neurotrophins and their cognate receptors are expressed also in
this cell type, in particular BDNF/TrkB, our aim is to specifically ablate
trkB from GABAergic interneuros or from a particular subset of
these neurons by the use of the cre-lox system. We have so far generated
a few new transgenic mice expressing the cre recombinase under
specific promoters in bacterial artificial chromosomes (BACs).
We are using a similar approach to understand the in vivo relevance
of neurotrophins and their cognate receptors in neurodegenerative
disorders like Alzheimer’s and Huntington’s diseases.
Our long-term goals:
• to define molecular mechanisms regulating synaptic plasticity;
• to understand the molecular basis of neurodegeneration;
The PLCγ site, and subsequent phosphorylation of calcium
calmodulin kinase/s and CREB couples learning and parallel
changes in hippocampal synaptic plasticity in vivo.
• to understand mechanisms underling neuronal diversification.
Selected references
Serguera, C., Triaca, V., Kelly-Barrett, J., Banchaabouchi, M.A. &
Minichiello, L. (2008). Increased dopamine after mating impairs
olfaction and prevents odor interference with pregnancy. Nat.
Neurosci., 11, 99-956
Gruart, A., Sciarretta, C., Valenzuela-Harrington, M., Delgado-Garcia,
J.M. & Minichiello, L. (2007). Mutation at the TrkB PLCγ-docking site
affects hippocampal LTP and associative learning in conscious mice.
Learn. Mem., 1, 5-62
112
Calella, A.M., Nerlov, C., Lopez, R.G., Sciarretta, C., von Bohlen Und
Halbach, O., Bereshchenko, O. & Minichiello, L. (2007).
Neurotrophin/Trk receptor signaling mediates C/EBPα, -β and
NeuroD recruitment to immediate-early gene promoters in neuronal
cells and requires C/EBPs to induce immediate-early gene
transcription. Neural Develop., 2,
Medina, D.L., Sciarretta, C., Calella, A.M., von Bohlen Und Halbach,
O., Unsicker, K. & Minichiello, L. (200). TrkB regulates neocortex
formation through the Shc/PLCγ-mediated control of neuronal
migration. EMBO J., 23, 3803-381