Expression of the de novo DNA methyltransferases (dnmt3 – dnmt8) during zebrafish lens development

Abstract

De novo DNA methylation is thought to be critical for cellular reprogramming during tissue differentiation and development. Little is known about the roles of de novo DNA methylation during eye development, and particularly during lens development. The lens is composed of lens epithelial (LE) and lens fiber (LF) cells, with proliferative LE cells giving rise to differentiated LFs at the "transition zone." Given the unique architecture and developmental program of the lens, and the involvement of de novo DNA methylation during differentiation events in other tissues, we sought to identify de novo DNA methyltransferases expressed in the zebrafish lens. Zebrafish possess six de novo DNA methyltransferase genes, dnmt3 - dnmt8. At 24 hr postfertilization (hpf), all six are expressed ubiquitously throughout the eye. By 72 hpf, dnmt3 and dnmt5 become restricted to cells of the retinal ciliary marginal zone (CMZ), dnmt4 and dnmt7 to cells of the CMZ and LE, and dnmt6 and dnmt8 to ganglion cells and cells of the inner nuclear layer of the retina. These data identify regions of the eye where de novo methyltransferases could mediate DNA methylation events during development. Overlapping expression domains also suggest functional redundancy within this gene family in the eye.