Notably, as shown in Figure 1A, pso KC displayed higher mRNA levels of the senescent markers p16, p21 and p57, compared to healthy KC, whereas mRNA levels of Cdk1 and cyclin A, which promote the progression of cell cycle and cellular proliferation, were consistently down-regulated in pso KC (Figure 1A). The gene discussed is CCNA2; the disease is keratoconus.