BiP upregulation begins in Cx50 mutant lenses between E13.5 and E15.5. (A, B) WT E13.5 lenses exhibit a uniform BiP distribution which is also seen in E13.5 G22R/G22R (E,F) and E13.5 S50P/S50P (I, J) connexin mutants. In WT lenses, BiP levels begin to be relatively higher in the transition zone of E15.5 lenses (C, D), BiP levels are noticeably upregulated by E15.5 in both G22R/G22R (G, H) and S50P/S50P (K,L) lenses. (M,N) Quantitation of BiP levels in G22R/G22R and S50P/S50P homozygotes in the lens epithelium, transition zone and cortical fibers at E13.5 (M) and E15.5 (N) using ImageJ. P values reported represent ANOVA analysis performed on results obtained from at least three biological replicates. Red-BiP; Blue-DRAQ5 (DNA); e- epithelial cells; f- fiber cells; tz-transition zone; Panels A,B,E,F,I,J Scale bar 67 μm; Panels C,D,G,H,K,L Scale bar=71 μm.