 It can also induce a loss of cell polarity and epithelial-mesenchymal transition, leading to invasive and metastatic growth in mammary epithelial cells.The importance of c-fos in biological context has been determined by eliminating endogenous function by using anti-sense mRNA, anti-c-fos antibodies, a ribozyme that cleaves c-fos mRNA or a dominant negative mutant of c-fos.The transgenic mice thus generated are viable, demonstrating that there are c-fos dependent and independent pathways of cell proliferation, but display a range of tissue-specific developmental defects, including osteoporosis, delayed gametogenesis, lymphopenia and behavioral abnormalities.