COL4A1 and preeclampsia: As mentioned above, the polypeptide chains of Collagen type IV are encoded by six genes, including COL4A1, COL4A2, COL4A3, COL4A4, COL4A5 and COL4A6. A study identified that COL4A1 and COL4A2 as maternal preeclampsia susceptibility genes, which code for collagen type IV α chain 1 and α chain 2 132.