Figure 3. Mutant MYOC accumulates in the ER, induces ER stress, and activates UPR.

(A) Increased ER stress markers including Ire1, Grp78, Grp94, spliced Xbp-1, activated Atf-6α, and pelF-2α were detected in 6-month-old Tg-MYOC^Y437H anterior segment tissues by Western blot. These markers were also increased in 12-month-old Tg-MYOC^Y437H mice. (B) Immunostaining for KDEL (recognizes Grp78 and Grp94) in the iridocorneal sections of WT and Tg-MYOC^Y437H mice demonstrated increased ER stress marker localization in the TM of 6-month-old Tg-MYOC^Y437H mice compared with WT littermates (n = 4). (C) Decreased myocilin secretion in the aqueous humor of Tg-MYOC^Y437H mice. Representative Western blot of myocilin secretion in aqueous humor of Tg-MYOC^Y437H mice is compared with that in WT mice. (n = 6). (D) Mutant MYOC accumulates in the ER of primary TM cells. Colocalization of MYOC (red) with KDEL (green) was examined using immunostaining and confocal imaging in TM cells (n = 4). Scale bars: 20 μm. (E and F) Expression of mutant MYOC in the TM induces ER stress and elevates IOP. WT MYOC, Y437H MYOC, and G364V MYOC were expressed in the TM by adenoviral injections. Western blots of ER stress markers were examined in the iridocorneal angle tissues after 24 hours of injections (E), and IOP was examined (F). ***P < 0.005 versus WT, n = 12 WT MYOC, and 20 Y437HMYOC. Data are shown as mean ± SEM.