SOX2 Regulates P63 and Stem/Progenitor Cell State in the Corneal Epithelium

Abstract

Mutations in key transcription factors SOX2 and P63 were linked with developmental defects and postnatal abnormalities such as corneal opacification, neovascularization, and blindness. The latter phenotypes suggest that SOX2 and P63 may be involved in corneal epithelial regeneration. Although P63 has been shown to be a key regulator of limbal stem cells, the expression pattern and function of SOX2 in the adult cornea remained unclear. Here, we show that SOX2 regulates P63 to control corneal epithelial stem/progenitor cell function. SOX2 and P63 were co‐expressed in the stem/progenitor cell compartments of the murine cornea in vivo and in undifferentiated human limbal epithelial stem/progenitor cells in vitro. In line, a new consensus site that allows SOX2‐mediated regulation of P63 enhancer was identified while repression of SOX2 reduced P63 expression, suggesting that SOX2 is upstream to P63. Importantly, knockdown of SOX2 significantly attenuated cell proliferation, long‐term colony‐forming potential of stem/progenitor cells, and induced robust cell differentiation. However, this effect was reverted by forced expression of P63, suggesting that SOX2 acts, at least in part, through P63. Finally, miR‐450b was identified as a direct repressor of SOX2 that was required for SOX2/P63 downregulation and cell differentiation. Altogether, we propose that SOX2/P63 pathway is an essential regulator of corneal stem/progenitor cells while mutations in SOX2 or P63 may disrupt epithelial regeneration, leading to loss of corneal transparency and blindness. Stem Cells 2019;37:417–429

Capturing limbal epithelial stem cell population dynamics, signature, and their niche

“…In vitro experiments: Human limbal rings from cadaveric corneas were obtained under the approval of the local ethical committee and declaration of Helsinki. Cells cultivation, differentiation, transfection, Western blot and real time polymerase chain reaction (qPCR) analyses were performed as previously described 101 . We used esiRNA against EGFP (EHUEGFP, Sigma), IFITM3 (EHU222801, Sigma) or GPHA2 (EHU036941, Sigma) and cells were collected 5-6 days after transfection.…”

Modulation of Wnt/BMP pathways during corneal differentiation of hPSC maintains ABCG2-positive LSC population that demonstrates increased regenerative potential

“…Markers that allow purification of the clinically relevant cell material by sorting would significantly promote both the safety and efficacy of the future treatments [17]. However, this issue is complicated by the fact that a low level of pluripotency markers is also expressed in the primary human limbal epithelium [18], and some of these markers are critically involved in the regulation of stemness [19]. A thorough understanding of the LSC differentiation hierarchy and the functional roles of various LSC-related markers is required to be able to address these questions.…”

Epigenetic regulation of anterior segment diseases and potential therapeutics

“…A follow-up study in 2015 by the same group found that miRs-103 and 107 enhances proliferation through different targets, including kinase p90RSK2, Wnt3a, NEDD9 (HEF1), and tyrosine phosphatase PTPRM 75 . On the other hand, miR-450b stimulates differentiation of limbal cells by repressing the SOX2/P63 pathway 80 .…”