Examination of the mab21l1-c.107delA p.(Lys36Argfs*7) ocular phenotype using immunohistochemistry, PAS staining and TUNEL fluorescence assays. A-I′, Wild-type, A-I, and mab21l1c.107delA mutant, A′-I′, transverse sections from 5-dpf, A-C, A′-C′), 1-mpf, D-F, D′-F′, and adults (1–2 years of age), G-I, G′-I′, were stained with DAPI (blue), cdh2 (green), and CKS (red). At 5-dpf, cdh2, and CKS staining highlights a thinner corneal epithelium (B′ vs. B) and stroma (C′ vs. C), correspondingly, observed in some mab21l1c.107delA embryos. At 1-mpf, thinning of the mab21l1c.107delA corneal epithelium (cdh2; E′ vs E) and stroma (CKS; F′ vs. F) becomes even more pronounced (red arrows in D′-F′). In mab21l1c.107delA adults, disorganized corneal layers with ectopic staining of CKS that can be detected throughout the outermost layer of the cornea (typically epithelium) are observed (I′ vs. I; red arrowhead in I′); additionally, lens degeneration is evident, highlighted by the absence of the cuboidal-shaped lens epithelial cells and disorganized cdh2 staining inside the lens (red arrowheads and asterisks in G′ and H′). (ce) corneal epithelium; (le) lens epithelium; (cs) corneal stroma; (cn) corneal endothelium. J-K′, Periodic acid-Schiff staining. Wild-type, J and K, and mab21l1c.107delA, J′,K′, adults (1–2 years of age) transverse sections were PAS stained to visualize mucin-secreting goblet cells. In wild-type adults, PAS-stained mucin-secreting goblet cells are restricted to the peripheral ocular tissue (J, black asterisks), and cannot be detected within the central cornea (K inset). In mab21l1c.107delA adults, PAS-stained goblet cells can be found at the ocular peripheries (J′, black asterisks), but can also be detected throughout the central cornea (J′ red asterisks, K′ inset red arrowheads). Red arrows in J′, K′ indicate abnormal corneal structures. (c) cornea; (l) lens; (r) retina, (ir) iridocorneal region; (ce) corneal epithelium; (cs) corneal stroma. L, Quantification of TUNEL assay. TUNEL positive cells were counted and percentage calculated to total DAPI-stained cells in cornea. Statistical significance is indicated by asterisks (1-mpf **P = .0021; Adult **P = .0081); error bars indicate SEM. M-O′. Representative images of TUNEL-stained wild-type, M,N,O, and mab21l1c.107delA mutant, M′, N′, O′, transverse sections at 5-dpf, M,M′, 1-mpf, N,N′, and adult, O, O′, eyes (red indicates dead cells). DAPI (blue) indicates cell nuclei. At all stages, an increase in TUNEL-stained cells was observed in mab21l1c.107delA mutant cornea (indicated by red arrows in, M′, N′ and O′, compared with wild-type. (c) cornea; (l) lens
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