Development and Evolution of Cell Behavior and Interactions during Danio Pattern Formation

Abstract

Danio fishes offer a tractable system for elucidating mechanisms of pattern formation and how they evolve, as fishes in this genus display a diverse array of pigment patterns that arise from a common set of cell types. Zebrafish (Danio rerio) forms its adult pattern beginning with a primary interstripe of densely packed iridescent iridophores and yellow xanthophores, with dark stripes of black melanophores and loose iridophores forming dorsally and ventrally. Additional interstripes and stripes are then reiterated to yield the final adult pattern. Stripe formation requires positive and negative interactions between pigment cells and between pigment cells and their environment, but the specific cell behaviors underlying morphogenesis are just beginning to be understood. Here I use time-lapse imaging, cell marking, and other genetic approaches to identify new features of iridophore morphogenesis and differentiation in zebrafish and manipulative experiments to dissect iridophore behavior during pattern formation. Additionally, I explore how changes in pigment cell-cell communication and global hormonal signals have evolved in the closely related species, pearl danio, whose uniform pattern is in stark contrast to zebrafish stripes. Together these data advance our understanding of a rapidly growing model of Danio pigment pattern formation and how the evolution of cellular interactions gives rise to the stunning diversity of adult form.