CRTAP and osteogenesis imperfecta: The subtle nature of this abnormality is confirmed by the absence of proteinuria by dipstick analysis in both our Crtap-/- mice (data not shown) and in the OI patients with hypercalciuria [24], as well as the normal levels of serum and urinary calcium, phosphorous, and magnesium previously reported in the Crtap-/- mice [1].