Intracellular Microinjection: A Powerful Tool in the Study of Neuronal Gene Expression and Function

Neurons in primary culture provide a useful experimental system with which to explore the functions of neuronal genes and the mechanisms regulating their expression. Both types of study call for transfection of neurons with plasmid DNA constructs that express either the gene of interest or a reporter gene under the transcriptional control of sequences from the gene being studied. However, the phenotypic heterogeneity and limited cell numbers that are often a feature of primary neuronal culture preparations mean that methods commonly used for bulk transfection and analysis of cell line cultures are inappropriate or difficult to apply. Intracellular microinjection provides the experimenter with the means to direct transfection into a specific cell type with high efficiency and is ideally suited for work with small cell numbers. Moreover, developments in microinjection technology and in methods of analyzing gene expression in small numbers of cells mean that many of the apparent limitations of the technique are now being overcome. The microinjection procedures that have been used in our laboratory to study neuropeptide gene expression in cultured mature mammalian sensory neurons are described.