Role of Cytokines in Demyelinating Disease Studied in Transgenic Mice

The pathogenesis of inflammatory demyelinating diseases of the central nervous system (CNS) is complex and in part reflects the contribution of multiple cellular and molecular factors. Determining whether these factors are primary or secondary to lesion development or are pathogenic versus protective or reparative represents a major research challenge and will be critical in the development of effective therapeutic strategies. The recent development of experimental procedures that permit the stable germline transmission in mice (so-called transgenic mice) of specific genes with expression targeted to the intact CNS offers a powerful new approach for tackling this problem. In this paper we discuss our experience in the application of genetic engineering to develop transgenic mice with the astrocyte-targeted expression of the key mediators of the host response, the cytokines. Cytokines are a large family of pluripotent mediators with specific classes of these molecules being incriminated in the pathogenesis of inflammatory demyelinating diseases. Transgenic mice were developed in which the expression of the cytokines interleukin-6 or interleukin-3 was targeted to astrocytes using a glial fibrillary acidic protein genomic expression vector. Depending on which cytokine was expressed, these animals developed white matter disease with distinct patterns of demyelination associated with different pathologic features. Here we will describe the procedural details associated with the development of these transgenic models, focusing on three general themes: (i) production of transgenic animals, (ii) analysis of transgene expression, and (iii) characterization of the transgenic mouse phenotype.