Region-directed phototransfection reveals the functional significance of a dendritically synthesized transcription factor.

Multiple nuclear transcription factors including E-26-like protein 1 (Elk-1) have been found in neuronal dendrites, yet the functional significance of such localization has not yet been explained. Here we use a focal transfection procedure, 'phototransfection', to introduce Elk1 mRNA into specific regions of live, intact primary rat neurons. Introduction and translation of Elk1 mRNA in dendrites produced cell death, whereas introduction and translation of Elk1 mRNA in cell bodies did not produce cell death. Elk-1 translated in dendrites was transported to the nucleus, and cell death depended upon transcription, supporting the dendritic imprinting hypothesis and highlighting the importance of the dendritic environment on protein function. Our demonstration of the utility of phototransfection for spatially controlled introduction of mRNAs opens the broader opportunity to use this method to introduce selected quantities of small molecules into discrete regions of live cells to assess their biological functions.