EURON and THEME joint PhD meeting
EURON and THEME joint PhD meeting
EURON and THEME joint PhD meeting
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49<br />
<strong>EURON</strong> <strong>and</strong> <strong>THEME</strong> <strong>joint</strong> <strong>meeting</strong> 2011<br />
Labelling <strong>and</strong> optogenetic manipulation of learningrelated<br />
neuronal assemblies.<br />
Holger Dannenberg, Milan Pabst, Karen van Loo, Albert Becker, Susanne Schoch,<br />
Heinz Beck<br />
Department of Epileptology <strong>and</strong> Life&Brain Center, University Bonn, Sigmund-Freud-Str. 25, 53105 Bonn,<br />
Germany.<br />
Learning is thought to correlate with an initial change in the dynamics of a<br />
specific assembly of neurons <strong>and</strong> a subsequent sustained change in the synaptic<br />
connections between them. The propensity of this particular assembly of neurons<br />
to be recruited into synchronized activity can then be viewed as a memory trace.<br />
However, identifying these neuronal assemblies has been challenging.<br />
Immediate early gene promoters (IEGs) could be good c<strong>and</strong>idates to genetically<br />
label cell populations active in-vitro, <strong>and</strong> to subsequently drive expression of<br />
fluorescent markers or light-sensitive channels that allow specific millisecondscale<br />
modulation of cellular activity. We have first compared the hippocampal<br />
expression patterns of the IEGs Arc (also known as Arg3.1), Egr1 (also known as<br />
zif268) <strong>and</strong> c-fos after a spatial learning paradigm in rats. We found an increase<br />
in the number of cells in the hippocampus of trained rats <strong>and</strong>/or rats having<br />
explored a novel environment compared to a cage control group. The expression<br />
patterns showed a partial overlap with subregional differences between each of<br />
the IEGs.<br />
We first chose a core promoter from the Arc gene (termed synaptic-activityresponsive<br />
element, SARE) to drive expression of the light-activated inhibitory<br />
chloride-pump halorhodopsin (eNpHR3.0) fused to EYFP. We show that the<br />
adenoviral approach is suitable to express eNpHR3.0-EYFP in principal cells of the<br />
hippocampus <strong>and</strong> characterized the SARE activation pattern by comparing it with<br />
the expression pattern of Arc, Egr1, <strong>and</strong> c-fos. eNpHR3.0-EYFP expressing cells<br />
could be inhibited by photo-activation in acute hippocampal slices, confirming<br />
its functionality in vitro. These approaches may permit the light-based activation<br />
or inhibition of neurons participating in the neuronal engram, both in-vitro <strong>and</strong><br />
in-vivo.