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The dynamics of epithelial stem cells (SCs) that contribute to the formation and maintenance of the cornea are poorly understood. Here, we used K14CreER T2 -Confetti (Confetti) mice, sophisticated imaging, and computational modeling to trace the origins and fate of these cells during embryogenesis and adult life. We show that keratin-14 (K14 + )-expressing progenitors are defined and widely distributed across the E16.5 cornea, after which they undergo cycles of proliferation and dispersal prior to eyelid opening. K14 + clonal patches disappear from the central cornea and are replaced by limbal-derived K14 + streaks, a finding that aligned with bromodeoxyuridine label-retaining studies. We also elucidated the mechanism by which SC clones are lost during life and propose this is due to population asymmetry and neutral drift. Finally, we established that the occurrence of an equatorial migratory mid-line is a consequence of apoptosis in a narrow nasal-temporal region, the site where eyelids meet during blinking., (Copyright © 2017 The Authors. Published by Elsevier Inc. All rights reserved.)

Stem cell (SC) division, deployment, and differentiation are processes that contribute to corneal epithelial renewal. Until now studying the destiny of these cells in a living mammal has not been possible. However, the advent of inducible multicolor genetic tagging and powerful imaging technologies has rendered this achievable in the translucent and readily accessible murine cornea. K14CreER(T2)-Confetti mice that harbor two copies of the Brainbow 2.1 cassette, yielding up to 10 colors from the stochastic recombination of fluorescent proteins, were used to monitor K-14(+) progenitor cell dynamics within the corneal epithelium in live animals. Multicolored columns of cells emerged from the basal limbal epithelium as they expanded and migrated linearly at a rate of 10.8 µm/day toward the central cornea. Moreover, the permanent expression of fluorophores, passed on from progenitor to progeny, assisted in discriminating individual clones as spectrally distinct streaks containing more than 1,000 cells within the illuminated area. The centripetal clonal expansion is suggestive that a single progenitor cell is responsible for maintaining a narrow corridor of corneal epithelial cells. Our data are in agreement with the limbus as the repository for SC as opposed to SC being distributed throughout the central cornea. This is the first report describing stem/progenitor cell fate determination in the murine cornea using multicolor genetic tracing. This model represents a powerful new resource to monitor SC kinetics and fate choice under homeostatic conditions, and may assist in assessing clonal evolution during corneal development, aging, wound-healing, disease, and following transplantation., (© 2014 AlphaMed Press.)