Gene expression profile in prion protein-deficient fibroblasts in culture

To Investigate the physiological function of the cellular isoform of prion protein (PrPC), the gene expression profile was studied by analyzing a cDNA expression array containing 597 clones of various functional classes In tw o distinct skin fibroblast cell lines designated SFK and SFH, established f rom PrP-deficient (PrP-/-) mice and PrP+/+ mice, respectively. The cells we re incubated In the culture medium with or without inclusion of baste fibro blast growth factor (bFGF), When SFK cells were compared with SFH cells in untreated conditions, the expression of 15 genes, including those essential for cell proliferation and adhesion, was reduced, whereas the expression o f 27 genes, Including those Involved In the insulin-like growth factor-I (I GF-I) signaling pathway, was elevated. Northern blot analysis verified a si gnificant down-regulation of the receptor tyrosine kinase substrate Eps8, c yclin D1, and CD44 mRNAs, and a substantial up-regulation of phosphatidylin ositol 3-kinase p85, IGF-I, and serine protease Inhibitor-2.2 mRNAs in SFK cells. The patterns of induction or reduction of gene expression after expo sure to bFGF showed considerable overlap between both cell types. Furthermo re, both Eps8 and CD44 mRNA levels were reduced greatly In the brain tissue s of the cerebrum isolated from the PrP-/- mice. These results indicate tha t the disruption of the PrP gene resulted in an aberrant regulation of a ba ttery of genes important for cell proliferation, differentiation, and survi val, Including those located in the Ras and Rac signaling pathways.