Wednesday, November 16, 2011

Cell-specific markers in the Vestibular Nuclei!

Yesterday I met my heroine in Cerebellar electrophysiology. Sacha Du Lac runs a lab at SALK that has basically done all identification of cell types in the vestibular nuclei. This started back in the early 2000's and is continuing since. They used the GIN, YFP-16 and GlyT2 mouse lines to label three neuronal classes in the vestibular nuclei. These mouselines have been used before and provide labeling of (putative) GABAergic, glutamatergic and glycinergic neurons. However from early morphological work in the 1960's from Chan-Palay it is clear that there are more than three classes of neurons, probably five or six classes. How to resolve this discrepancy? Electrophysiology is not the way to go since the classes show a continuum of electrophysiological parameters. In other words, there are no clear electrophysiological markers for these cells.

The people at SALK used a different approach: they used single cell RT PCR to construct single cell cDNA libraries of ~100 genes for ~150 individual cells. This library was then used to construct a clustering of cell types and genes. From this analysis six clear subtypes emerged. All six subtypes can be easily described by the exclusive expression of one or two genes. Of course this is awesome news since it seems possible to make cell-specific transgenic lines (Did I hear anyone scream optogenetics again?). Unfortunately, since the mouselines are not available yet, they didn't have any electrophysiology or morphological data on the subclasses, let alone a wiring diagram of the nuclei.

It goes to show that things are often more complicated than we thought. Or, just as complicated as people suspected decades ago.

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