TRAF6 and fleck corneal dystrophy: And in lesion tissue, the expression ratio of K63 polyubiquitin to TRAF6 was increased, compared to that in peri-FCD tissue (1.449 ± 0.201 vs. 0.305 ± 0.124, P < 0.01; Fig. 1d), indicating that ubiquitination of TRAF6 was increased in FCD lesion.