Expression data from mouse cerebral cortex

Cerebral cortex consists of many functional areas that are interconnected via direct axon projections from long association neurons. Long association neurons are located in layers 2/3, 5, and 6b. These neurons are intermingled with callosal neurons, which connect both cerebral hemisphere, in layers 2/3 and 5. To We used microarrays to compare gene expression profiles of long association neurons and callosal neurons in order to understand genetic programs that specifies these neuronal subtypes. Long association neurons and callosal neuorns in the primary somatosensory area (S1) were labeled by retrograde tracing from the primary motor area (M1) and the S1 on the contralateral hemisphere. 3 days after the tracer injection, mice were perfused with cold PBS, brains were dissected out, and fresh frozed sections were prepared. Labeled neurons were collected one by one with laser microdissection from each layer separately and subjected to total RNA preparation and hybridization on Affymetrix microarrays.