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L. Xu, T.-K. Ng, C.-P. Pang, H.-F. Yam; Unfolded Protein Response in Mouse Stage-Specific Retinal Progenitor Cells. Invest. Ophthalmol. Vis. Sci. 2010;51(13):2656.
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© ARVO (1962-2015); The Authors (2016-present)
To investigate the patterning of unfolded protein responses (UPR) in retinal progenitor cells in mice at early or late embryonic (E) stages and compared with retinal cells from postnatal (PN) stages.
Encleated eyes from Balb/C mice of age at E12, E18 and PN7 were dissected to obtain retina. Dissociated single retinal cells were expanded in neural basal medium containing N2 supplement, epidermal growth factor and basic fibroblast growth factor for neurosphere formation. At day 7, neurospheres were collected, dissociated to single cells and treated with 5 µg/ml tunicamycin for 2 hours to induce ER stress by preventing global N-linked glycosylation. The expression of UPR markers, BiP/GRP78, calreticulin, GADD153/CHOP and retinal differentiation marker, neuron-specific enolase, was examined by western blotting and immunofluorescence, respectively. Apoptosis rate was represented by percentage of TUNEL positive cells.
Protein analyses showed that, in retina tissues, the level of BiP expression induced in E12 cells was about 12-fold more than that in E18 and PN7 cells. Assay of molecular chaperones, including calreticulin and protein disulfide isomerase, showed similar changes. GADD153/CHOP level was also found higher in E12 versus E18 or PN7 cells. E12 cells under tunicamycin treatment had the least induced apoptosis, whereas PN7 cells had the highest apoptotic rate. In addition, most treated E12 cells were positive for neuron-specific enolase. The level was reduced in E18 cells.
Early progenitor cells possessed a specific mechanism to protect against ER stress. The upregulation of BiP and molecular chaperones helped the cells resolve the ER stress problem and maintained the stem cell survival. Our result demonstrated a differential UPR patterning in early embryonic progenitor cells when compared to late progenitor cells. A different adaptive mechanism may be recruited to confront with the ER overloading situation in cells of early embryonic stages.
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