Histones, Their Variants and Post-translational Modifications in Zebrafish Development

Abstract

Complex multi-cellular organisms are shaped starting from a single-celled zygote, owing to elaborate developmental programs. These programs involve several layers of regulation to orchestrate the establishment of progressively diverging cell type-specific gene expression patterns. In this scenario, epigenetic modifications of chromatin are central in influencing spatiotemporal patterns of gene transcription. In fact, it is generally recognized that epigenetic changes of chromatin states impact on the accessibility of genomic DNA to regulatory proteins. Several lines of evidence highlighted that zebrafish is an excellent vertebrate model for research purposes in the field of developmental epigenetics. In this review, I focus on the dynamic roles recently emerged for histone post-translational modifications (PTMs), histone modifying enzymes, histone variants and histone themselves in the coordination between the precise execution of transcriptional programs and developmental progression in zebrafish. In particular, I first outline a synopsis of the current state of knowledge in this field during early embryogenesis. Then, I present a survey of histone-based epigenetic mechanisms occurring throughout morphogenesis, with a stronger emphasis on cardiac formation. Undoubtedly, the issues addressed in this review take on particular importance in the emerging field of comparative biology of epigenetics, as well as in translational research.

Keywords: development; epigenetics; histone; histone posttranslational modifications; histone variants; maternal-to-zygotic transition; zebrafish; zygotic genome activation.

FIGURE 1

Diagrammatic representation of key epigenetic changes occurring during early zebrafish embryogenesis. Simplified drawings on the top depict some of the developmental stages, while developmental and epigenetic trends are illustrated below (see main text for details). Please note that placeholder nucleosomes retain parental histone modification patterns throughout early embryogenesis, and that cohesin complex recruitment is restored at 24 h post-fertilization. PTM, post-translational modification; TFs, transcription factors; ZGA, zygotic genome activation.