Based on the results from our expression and functional studies and the finding that other BMP ligands, such as BMP4, regulate the budding site and elongation of the developing mouse ureter [39], we propose that the rare GDF6 variants detected in five renal anomaly patients here and previously [17, 18] may be causally related to their kidney malformation. The gene discussed is BMP4; the disease is Abnormal renal morphology.