GDF15 and Nephropathy: Schledzewski et al. demonstrated that double knockout mice of Stab1 and Stab2 show glomerulofibrotic nephropathy due to accumulation of a transforming growth factor (TGF)-β family member growth differentiation factor 15 (GDF-15) and other ECM material in the blood, while single knockout mice of Stab2 are normal (18).