GPNMB and polycystic kidney disease: GPNMB and its homolog PMEL17, first identified as melanosomal proteins, share a similar domain structure encompassing a large luminal domain containing a N-terminal domain (NTR), a polycystic kidney disease-like domain (PKD) and a kringle-like domain (KRG), and an intracellular domain, also referred to as the C-terminal domain (CTD), with a dileucine-based lysosomal sorting signal27,28.