The zinc finger transcription factor GLI1, which mediates Sonic hedgehog signaling during development, is expressed in several human cancers, including basal cell carcinoma, medulloblastoma, and sarcomas. We identified 147 genes whose levels of expression were significantly altered in RNA obtained from cells demonstrating a transformed phenotype with stable GLI1 expression or stable Ha-ras expression. Comparison of expression profiles from GLI1-and Ha-ras-expressing cells established a set of genes unique to GLI1-induced cell transformation. Thirty genes were altered by stable GLI1 expression, and 124 genes were changed by stable Ha-ras expression. Seven genes had altered expression levels in both GLI1-and Ha-ras-expressing cells. Genes whose expression was altered by GLI1 included cell cycle genes, cell adhesion genes, signal transduction genes, and genes regulating apoptosis. GLI1 consensus DNA-binding sequences were identified in the 5 regions of cyclin D2, IGFBP-6, osteopontin, and plakoglobin, suggesting that these genes represent immediate downstream targets. Gel shift analysis confirmed the ability of the GLI1 protein to bind these sequences. Up-regulation of cyclin D2 and down-regulation of plakoglobin were demonstrated in GLI1-amplified compared with non-amplified human rhabdomyosarcoma cells. Many of the GLI1 targets with known function identified in this study increase cell proliferation, indicating that GLI1-induced cell transformation occurs through multiple downstream pathways.Important gene hierarchies, in part coding for components of signal transduction pathways, regulate growth and differentiation during development. One such pathway is the Sonic hedgehog-Patched-Gli pathway (1). SHH 1 signaling is critical to the genetic specification of fate of many tissues during early organogenesis including the central nervous system (2, 3), lung (4), prostate (5), bone (6 -8), and muscle (9). SHH signaling is mediated by the GLI family of transcription factors (10). One of these genes, GLI1, has been shown to be a transcriptional activator operating through a C-terminal VP-16-like acidic helical domain (11). GLI1 transforms cells in culture, and its expression is associated with significant human cancers including basal cell carcinoma (12), medulloblastoma (13), and sarcomas (14). Few downstream targets of GLI1 are known, which precludes a clear understanding of its action in carcinogenesis. Genetic evidence suggests that PTCH and Wnt genes are downstream targets of GLI1 (15), and biochemical evidence has established HNF-3␤ (Hepatocyte Nuclear Factor-3␤) as a target of GLI1 during development (16).Microarray technology has provided a methodology to study the expression of thousands of genes simultaneously and has been used in many important settings (17). Among these is the dissection of signal transduction pathways. To identify unique downstream targets of GLI1, we have utilized a cell transformation phenotype as a selection system for the stable integration and expression of either GLI1 or Ha-ras in RK3...

Peroxisome proliferator-activated receptors (PPARs) are members of the nuclear receptor superfamily and function as ligandmodulated transcription factors that regulate gene expression in many important biological processes. The PPAR␦ subtype has the highest expression in the brain and is postulated to play a major role in neuronal cell function; however, the precise physiological roles of this receptor remain to be elucidated. Herein, we show that the high-affinity PPAR␦ agonists L-165041 [4-[3-(4-acetyl-3-hydroxy-2-propylphenoxy)-propoxyl]phenoxy]-acetic acid] and GW501516 [2-methyl4-((4 -methyl-2-(4-trifluoromethylphenyl) -1,3 -triazol-5-yl)-methylsulfanyl)phenoxy acetic acid] protect against cytotoxininduced SH-SY5Y cell injury in vitro and both ischemic brain injury and 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) neurotoxicity in vivo. In the SH-SY5Y studies, treatment with L-165041 or GW501516 significantly and concentrationdependently attenuated cell death following thapsigargin, 1-methyl-4-phenylpyridinium, or staurosporine exposure, with the extent of damage correlated with the level of caspase-3 inhibition. In the transient (90 min) middle cerebral artery occlusion model of ischemic brain injury in rats, i.c.v. infusion of L-165041 or GW501516 significantly attenuated the ischemic brain damage measured 24 h after reperfusion. Moreover, the PPAR␦ agonists also significantly attenuated MPTP-induced depletion of striatal dopamine and related metabolite contents in mouse brain. These results demonstrate that subtypeselective PPAR␦ agonists possess antiapoptotic properties in vitro, which may underlie their potential neuroprotective potential in in vivo experimental models of cerebral ischemia and Parkinson's disease (PD). These findings suggest that PPAR␦ agonists could be useful tools for understanding the role of PPAR␦ in other neurodegenerative disorders, as well as attractive therapeutic candidates for stroke and neurodegenerative diseases such as PD.

Pharmacogenomics offers the potential to define metabolic pathways and to provide increased knowledge of drug actions. We studied relative levels of gene expression in the rat using a microarray with 8448 rat UniGenes (1928 known genes, 6520 unknown ESTs) in the liver and kidney as a function of time of day and then of feeding regime, which are common variables in preclinical pharmacogenomic studies. We identified 597 genes, including several key metabolic pathways, whose relative expression levels are significantly affected by time of day: expression of some was further modified by feeding state. These would have sparked interest in a pharmacogenomic study. Our study demonstrates that two common variables in pharmacogenomic studies can have dramatic effects on gene expression. This study provides investigators with baseline information for both kidney and liver with respect to 'normal' changes in gene expression influenced by time of day and feeding state. It also identifies 18 new genes that should be investigated for a role in circadian rhythms in peripheral tissues.