Gene-expression analysis at the single-cell level

The manner in which a cell responds to and influences its environment is ul timately determined by the genes that it expresses. To fully understand and manipulate cellular function, identification of these expressed genes is e ssential. Techniques such as RT-PCR enable examination of gene expression a t the tissue level. However, the study of complex heterogeneous tissue, suc h as the CNS or immune system, requires gene analysis to be performed at mu ch higher resolution. In this article, the various methods that have been d eveloped to enable RT-PCR to be performed at the level of the single cell a re reviewed. In addition, how, when carried out in combination with techniq ues such as patch-clamp recording, single-cell gene-expression studies exte nd our understanding of biological systems is discussed.