In species with heteromorphic sex chromos omes, the heterogametic sex (male XY and female ZW) carries only half of the sex-chromosomal genes. This can lead to disruption of gene regulatory networks or unbalanced gene expression in the heterogametic sex, such that different dosage compensation mechanisms have evolved to balance male and female gene expression. Histone H4 lysine 16 acetylation (H4K16ac) has a role in dosage compensation in male (XY) fruit flies and Anolis lizards, as well as in female (ZW) monarch butterflies. Writing in PLoS Genetics, Zimmer et al. analysed sex-specific patterns of H4K16ac across seven arthropods to determine how broadly it affects dosage compensation. Immunofluorescence staining and genome-wide chromatin profiling showed that H4K16ac mediates dosage compensation in two closely related dipterans (the fruit fly Drosophila melanogaster, XY, and the fungus gnat Bradysia coprophila, XO) and one ZW crustacean (Artemia franciscana) but not in a distantly related dipteran (Anopheles gambiae), a beetle (Leptinotarsa decemlineata) and a stick insect (Bacillus grandii) with ancient X chromosomes, nor in a termite (Reticulitermes flavipes) that has recently transitioned to an XY system from an ancestral XO one. Altogether, these data show convergent evolution of H4K16ac-mediated dosage compensation in insect and crustacean lineages and suggest that other mechanisms of dosage compensation are probably present in arthropods with XY and ZW sex chromosomes. A closer look at H4K16ac enrichment in A. franciscana revealed that it is restricted to the older region of the Z chromosome, which does not recombine with the W chromosome. Similarly to all known dosage-compensation mechanisms, the authors show that H4K16ac-mediated dosage compensation is established in the early stages of embryogenesis in A. franciscana but observed key differences in sex-specific regulation involving H4K16ac when comparing Artemia and Drosophila systems.
Original reference: PLoS Genet. 21, e1011895 (2025)
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