COL4A1 and keratoconus: In conclusion, the study claimed that six mRNAs (including PPARG, HLA-B, COL4A1, and COL4A2), five miRNAs (including upregulated miR-128, miR-32, miR-221 and downregulated miR-181a, miR-222, miR-98, miR-301a), nine lncRNAs (including XIST—X-inactive specific transcript—a non-coding RNA on the X chromosome that acts as a major effector of the X-inactivation process), and the XIST-miR-181a-COL4A1 axis are involved in the keratoconus-associated RNA regulatory network [45].