Abstract
The genome project elucidates that the whole genome possesses approximately 25,000 genes. Although it is thought that single cells express approximately 10,000 genes in various copy numbers in a cell-type specific manner, differences of gene expressions inside and among defined cell-types are not examined at a single cell level. Here, we examined mRNA expressions in acute rat hippocampal slices where the classification of cell types was most extensively examined. CA1 and CA3 pyramidal cells, dentate granule (DG) cells and interneurons were identified from their morphologies and the locations and cellular contents were harvested into patch pipettes. We performed RT-multiplex PCR of 31 genes, including biochemical markers of calcium binding proteins, neuropeptides and neurotransmitter receptors. Detection rates of each mRNA were examined. Except for correlations linked to glutamatergic and GABAergic neuronal markers, strong correlations were scarcely found. When cells were grouped according cell types, however, large differences of detection rates in many genes were observed. χ-square analysis revealed that 37% of tested genes were differently expressed in interneurons and principal neurons and that 30% were differently expressed in pyramidal cells and DG cells. Genes differentially expressed between CA1 and CA3 pyramidal neurons were not found. Dendrogram showing the distances of cell types was obtained by cumulative differences of detection rates. [J Physiol Sci. 2006;56 Suppl:S86]
