Minichiello Group (Visiting)
Signalling mechanisms and gene regulation in the nervous system
Previous and current research
The PLCγ site, and subsequent phosphorylation of calcium calmodulin kinase/s and CREB couples learning and parallel changes in hippocampal synaptic plasticity in vivo.
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 (figure 1), 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 are:
- to define molecular mechanisms regulating synaptic plasticity;
- to understand the molecular basis of neurodegeneration;
- to understand mechanisms underling neuronal diversification.