Whilst the osteopenia observed in osteoblast-specific Gab1 knockout mice has been linked to impaired IGF-1/insulin signaling via both PI3K and Ras pathways (Weng et al., 2010), recent data suggests the mitogenic effect of IGF-1 requires both pathways, whilst differentiation relies on PI3K/AKT signaling (Raucci et al., 2008). The gene discussed is IGF1; the disease is Osteopenia.