Expression profiling of lung tissue from 6-, 10- and 14-week-old Fra2 transgenic male mice

The transcription factor complex AP-1 (Activator protein 1) is composed of Jun (c-Jun, JunB, JunD) and Fos proteins (c-Fos, FosB, Fra-1, Fra-2) which control a variety of stress responses, including cell proliferation, apoptosis, inflammation, wound healing, and cancer. Individual Fos proteins have been thoroughly studied in gain- and loss-of-function mouse models, which revealed important functions in bone cell proliferation and differentiation. We have recently demonstrated that loss of Fra-2 causes perinatal lethality and severe osteopenia due to several cellular defects, including a chondrocyte differentiation defect and a control of osteoclast survival and size. Moreover, we have reported a profibrogenic function of Fra-2 in transgenic mice, in which ectopic expression of Fra-2 in various organs resulted in generalized fibrosis with predominant manifestations in the lung. Fra-2 knock-out newborns have increased numbers and size of osteoclasts in vivo. The pulmonary phenotype observed in Fra-2Tg mice is characterized by vascular remodeling and obliteration of pulmonary arteries, which coincides with expression of osteopontin, an AP-1 target gene involved in vascular remodeling and fibrogenesis. These alterations are followed by inflammation; release of profibrogenic factors, such as IL-4, insulin-like growth factor 1, and CXCL5. The expression profiling study was performed to analyse changes in transcript levels in lung over a period of time. Total RNA of four mutant male animals at each time point (age: 6, 10 and 14 weeks) were hybridised versus a pool of total RNA of four wild type mice of the corresponding age. For each mutant animal, two technical chip hybridisations were performed, including a dye-swap experiment (in total, 8 hybridisation of each time point = 2 technical replicates x 4 biological replicates).