COL4A1 and snowflake vitreoretinal degeneration: Interestingly, MMP14, which activates pro-MMP2, was also previously reported to be upregulated in aorta of mice with a Col4a1 glycine mutation (Col4a1+/SVC G1064D) that is a well-established model of Col4a1-associated SVD (Figures S5A and S5B) (van Agtmael et al., 2005; Jones et al., 2016, 2019).