Altered cell fates of limbal stem cells in aniridia associated with PAX6 mutations

Abstract

Proper biological function of stem cells in tissues and organs relies on their correct cell fates, and transcription factors (TFs) play key roles in controlling cell fate. Altered cell fates of stem cells due to genetic mutations or other factors can lead to developmental and homeostatic abnormalities. Aniridia is caused by mutations that affect the transcription factor PAX6, and patients with aniridia suffer from congenital and progressive corneal opacification. This is at least partly due to deficient function of limbal stem cells (LSCs) located in the periphery of the cornea. To test the hypothesis that corneal opacity is associated with altered cell fates in LSCs of aniridia patients, we performed transcriptome analyses using two different types of stem cells derived from aniridia patients: induced pluripotent stem cells (iPSCs) and primary limbal stem cells (pLSCs). First, we differentiated iPSCs to obtain induced LSCs. Our transcriptome data showed that induced LSCs derived from aniridia patients do not have the same epithelial identity as normal cells, but instead have an enhanced neural or pluripotent identity. In parallel, we investigated whether patient‐derived pLSCs could adopt the cell fate of a similar epithelial cell type, specifically skin keratinocytes, which give rise to the non‐transparent epidermis. By comparing the transcriptomes of these two cell types, we observed a clear loss of the normal LSC fate in the aniridia pLSCs as compared to normal pLSCs. However, the gain of keratinocyte cell fate was not evident. These findings demonstrate the essential role of PAX6 function in determining the correct cell fate of LSCs.