In order to investigate the mechanisms underlying abnormal bone formation in XLH, proteins involved in the mineralization process, namely, osteopontin (OPN) and sclerostin, were analyzed in the calcaneus and the sacroiliac joints in control and Hyp mice (Moester et al., 2010; Boukpessi et al., 2017). The gene discussed is SPP1; the disease is X-linked hypophosphatemia.