Cortical interneurons contribute to the complex signal integration of the brain and are highly heterogeneous not only in their anatomy and firing properties but much more in their pattern of gene expression. To help elucidate this diversity, we are using a new genetic tool based on Cre recombinase-dependent viral vector (FLEX-rAAV) to control the expression of the fluorescent reporter gene mCherry (a monomeric variant of DsRed2 protein) with precise temporal and/or spatial specificity. In coronal slices from specific-Cre driver mice, only specific subpopulations of interneurons could be visualized with fluorescence, allowing for identification of individual for patch-clamp recording and subsequent morphological and molecular analysis. While the study of interneuron at single-cell level is a promising but difficult approach, we are developing a novel and high sensitive method for messenger RNA purification fully compatible with patch clamp experiments. More specifically, mRNA are selectively pulled from a single-cell without interacting with other RNA or DNA by intracellular injection of fluorescent superparamagnetic nanoparticles coated with short aptamers allowing specific hybridization with mRNA (see video below). {flv}PPT|600|450|1|{/flv}

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mRNA capture using new para-magnetic nanoparticles (upper panel: principle and technique, bottom left: orientation of nanobeads using a magnetic field, bottom right: in vivo injection of fluorescent nanoparticles) Combining FLEX-rAAV injection and mRNA purification assisted by magnetic capture-hybridization we attempt to perform a single cell transcriptomic analysis to establish the first gene expression profile of different interneuron subpopulations.

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