An attempt to isolate genes which concern with regional differentiation and evolution of the cerebral cortex

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Cerebral cortex of mammals is devided into seraval fuctional areas such as motor, visual, and orditory ares. Each areas are characterized with specific cytoarchtetures and neuroal connections. To investigate the structural and fuctional difference at the molecular level, we attempted to isolate genes which is expressed in a specific area of the cerebral cortex of the old-world monkey, Macaca fascicularis. Two areas, primary motor cortex (area 4 of Broadmann) and primary visual cortex (area 17 of Broadmann) are examined since the difference of the two areas are the biggest as judged by the cytoarchtechture. Poly (A) RNAs are prepared from these areas. Two approach 1) supression subtractive hybridization (SSH : Diachenko et al. (1996) PNAS 93 : 6025-6030)and 2) serial anaylisis of gene expression (SAGE : Velculescu et al. (1995) Science 270 : 484-487) were employed.1) SSH : We have succeded in several preliminary conditioning experiments using mouse brain and mouse skeltal muscle. It was possible to isolate brain-specific and muscle-specific genes. However, monkey genes expressing in a area-specific mannar were not isolated.2) SAGE : We have sequenced about 1,500 tags from area 4 and 17. In order to obtain reliable data, we need to sequence ten times more tags. However, there are some technical problems to continue this methods. Technical improvements are required to continue this approach.Conclusion : It was not possible to isolate genes which are expressed in some specific area of the cerebral cortex using the two methods above. The difference of gene expression pattern between the two regions may be too small to analyze wiith the methods above. New approach such as differential display may be needed to isolate such genes.