SPP1 and diabetic kidney disease: Thus, transcription factor USF1 is thought to bind on the CCTCATGAC motif of the TGF-β1 promoter to induce renal fibrosis, and it binds on the same CCTCATGAC motif of the osteopontin promoter to induce glomerular enlargement with the synthetic phenotype and proliferation of MCs in diabetic nephropathy.