Optimizing Polyethylenimine-Based Gene Transfer into Mammalian Brain for Analysis of Promoter Regulation and Protein Function

The efficient and safe introduction of genes into the central nervous system (CNS) is a difficult, yet much sought after objective. Two broad classes of aims can be distinguished. On the one hand, there is therapy in which the ultimate target will be the modification of an endogenous gene by homologous recombination or the remedial addition of a gene coding for a deficient protein. On the other hand, there are analytical approaches in which the aim may be either to determine the physiological relevance of a given protein by blocking or by bolstering its expression, or to dissect the regulatory mechanisms impinging on promoter function in an integrated setting. Furthermore, analysis of promoter regulation will be a prerequisite for creating constructs with optimized regulatory sequences for expressing therapeutic proteins in physiologically appropriate conditions. Microinjection of different permutations of a specific promoter into defined brain regions is a rapid and inexpensive method for assessing function and for mapping transcriptional regulatory elements. Indeed, using somatic gene transfer can provide results that otherwise could only be obtained by labor-intensive germinal transgenosis, an approach that also requires a great deal of organizational prowess and expense for maintenance of the numerous lines created.