In vivo gene delivery to the postnatal ferret cerebral cortex by DNA electroporation.
Ferrets have been extensively used to unravel the neural mechanisms of coding and processing of visual information, and also to identify the developmental mechanisms underlying the emergence of such a complex and fine-tuned neural system. In recent years numerous tools have been generated that allow studying neural systems with unprecedented power. Unfortunately, because many of these tools are genetically encoded, they are having a limited impact on research involving "non-genetic" species, like ferret, cat and monkey. Here I show how in vivo electroporation can be performed in postnatal ferret kits to deliver genetic constructs to pyramidal neurons of the cerebral cortex. Electroporation of GFP- and DsRed-encoding plasmids results in labeling of cortical progenitors first, then migrating neurons, and finally differentiating neurons and their processes. This technique also allows for the genetic manipulation of cortical development in the ferret, as illustrated by electroporation of a dominant-negative form of Cdk5. In the mature brain of electroporated animals, expression of reporter genes reveals the detailed morphological traits of cortical pyramids, including their axonal and dendritic arborization, and dendritic spines. I also show that postnatal electroporation can be used for the transfection of a massive cortical territory, or it can be specifically directed to a subset of cortical areas, and even only to a few scattered pyramids along the cortical mantle. In vivo electroporation of postnatal ferrets is therefore an effective, rapid, simple and highly versatile method for delivering genetic constructs to this animal, optimal for both developmental studies and adult anatomical/functional studies.