Slc40a mRNA levels were measured by real-time RT-PCR and normalized to the levels of ribosomal protein S13 (Rps13) The Slc40a mRNA levels were similar in the SCD and control mice (Figure 3G, Fpn-Rps13 delta Ct, −3.926 ± 0.12 in SCD vs. −3.817 ± 019 in control, p = 0.6442). Here, RPS13 is linked to Schnyder corneal dystrophy.