2009/01/19

Define anatomic boundary by large scale expression pattern analysis

Genomic Anatomy of the Hippocampus
Thompson et al, Volume 60, Issue 6, 26 December 2008, Pages 1010-1021 -- Neuron

What features really define the boundaries of neural systems? Anatomical landmarks and morphology have long been the guide, but these criteria come with obvious caveats that, at the transition zone where one region morphs into another, the determination of the exact boundary may be somewhat arbitrary. Is there an abrupt transition? or graded transition? and are there hidden subdivisions?

The authors here provides novel insight on this issue using genome scale gene expression data. Thompson et al applied powerful statistical pattern recognition tools to determine functional domains within the hippocampus based on the spatial expression pattern of ~3000 genes. This analysis not only recovers the major divisions of the hippocampus - DG, CA3, CA1 - but also uncovers subdivisions within. I really like this data-driven approach, which relies on the same tools that are used to uncover patterns in neurophysiological data.

Many molecules that define the map are adhesion molecules, which are important for forming neuronal circuits and finding projection targets. Supporting this idea, the subdivisions described in this paper (lower row) correspond to the spatial divisions in several previous reports studying the input-output relations of the hippocampus with other regions (upper row). Thus, this approach provides the molecular underpinning for these subdivisions and identifies molecular targets that can uniquely specify a functional domain. On a broader perspective, the same approach can be applied to all brain regions and shed new light on the functional organization of the brain.

1 comment:

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