Epigenetic Regulation of Newt Lens Regeneration

Abstract

Purpose : Following lentectomy the newt is able to regenerate the lens from a subpopulation of iris cells in the dorsal iris, while an identical subpopulation of cells on the ventral iris lacks this regenerative capacity. In this system, ventral iris gene expression is highly plastic and reverts to a more stem/progenitor-like state, allowing for cells to reprogram to replenish the lost lens cells. We hypothesize that a global resetting of the epigenome is required for this regenerative reprogramming to take place.

Methods : Newt dorsal and ventral iris were assessed using RNA-seq to determine expression levels of key genes implicated in epigenetic regulation. Furthermore, DNA methylation marks and histone modifications in the newt iris were measured through immunofluorescence (IF) and 3D reconstruction of reprogramming nuclei. Finally, newt iris Chromatin compaction was measured using quantification of confocal images following lentectomy.

Results : Immunofluorescence of newt iris following lentectomy revealed that during regeneration, the repressive histone mark H3K27Me3 is selectively enriched in the ventral iris. In addition, extensive epigenetic remodeling was observed in the newt iris during regeneration, including acute changes in the DNA modifications 5mC and 5hmC. Analysis of chromatin compaction in newts revealed increased accessibility (i.e. more open chromatin) in dorsal iris when compared to ventral, indicating that increased chromatin accessibility plays a key role in regenerative capacity by moving the regenerating cells towards a plastic, progenitor-like cellular identity.

Conclusions : During regeneration, the dorsal newt iris undergoes marked changes in chromatin organization, particularly through increases in chromatin accessibility and resetting of epigenomic regulatory components. These modifications likely play an indispensable role in the regenerative process through their regulation of key genes.

This is a 2020 ARVO Annual Meeting abstract.