PAX6 Deficiency Compromises the Ability of Limbal Epithelial Stem Cells to Properly Differentiate Into Mature Corneal Epithelial Cells.

PURPOSE: Aniridia, driven by PAX6 mutations, causes aniridia-associated keratopathy (AAK), a progressive condition linked to limbal stem cell deficiency. A major hurdle to developing targeted therapies for AAK is the incomplete understanding of the molecular abnormalities in affected corneas. To address this, we leveraged Pax6± (Pax6 het) mice, a model of AAK, and applied single-cell RNA sequencing (scRNA-seq) to profile the transcriptomic changes at a single-cell resolution.

METHODS

ScRNA-seq of corneal/limbal tissues of wild type (WT) and Pax6 het mice were conducted. Immunostaining was performed to examine the expression of specific markers for stem cells.

RESULTS

ScRNA-seq identified a quiescent limbal epithelial stem cell (LESC)-like cell cluster and an early transient amplifying cell (eTAC)-like cluster. An increase in the cell numbers in these two clusters in the Pax6 het mouse corneas was observed. Immunostaining detected a marked increase in markers for these two clusters including Tmem176b, Apoe, and Krt15 in the corneal epithelium of Pax6 het mice, suggesting an increase of these LESC/eTA-like cells into the corneal epithelium. The Pax6 deficiency inhibited the expression of genes involved in cell proliferation in the eTAC-like cluster as well as the expression of genes related to corneal epithelial cell fate and differentiation compared with WT mice.

CONCLUSIONS

Our single cell transcriptome of the limbus and cornea of Pax6 het mice indicates that AAK may be due to the increase of dysfunctional stem/eTACs with defects in committing to a corneal epithelial cell fate and differentiation.