COL4A5 and Alport syndrome: Subsequent studies found that this renal dysfunction results from splitting of the glomerular basement membrane (GBM), hematuria, interstitial nephritis, and progressive kidney failure [2]; however, the genetic basis for Alport syndrome was unknown until mutations in the COL4A3, COL4A4, and COL4A5 collagen genes were discovered in clinically affected families [3–6].