Cell fate of müller cells during photoreceptor regeneration in an N-methyl-N-nitrosourea- induced retinal degeneration model of zebrafish

Zebrafish can regenerate several organs such as the tail fin, heart, central nervous system, and photoreceptors. Very recently, a study has demonstrated the photoreceptor regeneration in the alkylating agent N-methyl-N-nitrosourea (MNU)-induced retinal degeneration (RD) zebrafish model, in which whole photoreceptors are lost within a week after MNU treatment and then regenerated within a month. The research has also shown massive proliferation of Muller cells within a week. To address the question of whether proliferating Muller cells are the source of regenerating photoreceptors, which remains unknown in the MNU-induced zebrafish RD model, we employed a BrdU pulse-chase technique to label the proliferating cells within a week after MNU treatment. As a result of the BrdU pulse-chase technique, a number of BrdU+ cells were observed in the outer nuclear layer as well as the inner nuclear layer. This implies that regenerating photoreceptors are derived from proliferating Muller cells in the zebrafish MNU-induced RD model.