Furthermore, only ∼40% of c-fos −/− embryos survive until birth and surviving mice live to an average age of 6-7 months, show growth retardation, severe osteopetrosis, delayed or absent gametogenesis, altered hematopoiesis and abnormal behavior [10, 11], although the development of the Central Nervous System (CNS) of these c-fos −/− mice has not been studied up to date. This evidence concerns the gene FOS and osteopetrosis.