GLIAL-SPECIFIC AND FAT-SPECIFIC EXPRESSION OF THE RAT GLYCEROL PHOSPHATE DEHYDROGENASE-LUCIFERASE FUSION GENE IN TRANSGENIC MICE

Glycerol phosphate dehydrogenase (GPDH) is a metabolic enzyme that cat alyzes the conversion of dihydroxyacetone phosphate to glycerol-3-phos phate. It provides phospholipid precursors for lipid biosynthesis and energy metabolism. In the brain, GPDH enzymatic activity, protein, mRN A are exclusively associated with oligodendroglial and Bergmann glial cells. Expression of GPDH in the brain increases dramatically during t he active period of myelination, and is regulated by extracellular sig nals. In an effort to understand the mechanism that confers glial-spec ific expression of GPDH, we have examined the role of the 5' flanking sequence of the rat GPDH gene in conferring cell-specific expression o f reporter gene in transgenic mice, Luciferase reporter constructs con taining either the full-length GPDH 5' flanking region (p4.3), or a di stally truncated version (p2.6), were injected into mouse zygotes, Thr ee independent lines of transgenic mice containing the p4.3, and seven lines of mice containing the p2.6 constructs, were analyzed, Lucifera se enzyme activity was detectable only in brain and fat, not in other GPDH-positive organs such as liver, muscle, and kidney, Both the full- length and the distally deleted transgenes were expressed similarly in these two organs, indicating that the distal portion of the 5' flanki ng region was not required for brain-and fat-specific expression. Immu nocytochemical analyses revealed that luciferase immunoreactivity colo calized with glial fibrillary acidic protein (GFAP)-positive Bergmann glia in the cerebellum, and myelin basic protein (MBP)-positive oligod endroglia in the cerebral cortex and the brainstem, Results here sugge st that the rat GPDH 5' flanking region directs glial-specific express ion of GPDH transcription in the brain, and provide a good model for a nalyses of changes in glial metabolism in response to extracellular pe rturbations in vivo. (C) 1997 Wiley-Liss, Inc.