Transient chromatin decompaction at the start of D. melanogaster male embryonic germline development

TL;DR

Early in fruit fly male germline development, chromatin briefly becomes less compact, suggesting a conserved epigenetic reprogramming process.

Contribution

The study identifies a transient chromatin decompaction phase in Drosophila male germline cells, suggesting conserved epigenetic reprogramming.

Findings

Male germline chromatin undergoes a brief remodeling phase after zygotic activation.

Nucleosome density decreases and shifts away from promoter regions during this phase.

Enrichment analysis highlights factors involved in large-scale chromatin reorganization.

Abstract

Our genomics profiling of the earliest fruit fly germline revealed a brief window of major chromatin remodeling in the male germline right after zygotic activation and suggests reprogramming in the early stages of germline to be an evolutionarily conserved phenomenon.

Embryonic germ cells develop rapidly to establish the foundation for future developmental trajectories, and in this process, they make critical lineage choices including the configuration of their unique identity and a decision on sex. Here, we use single-cell genomics patterns for the entire embryonic germline in Drosophila melanogaster along with the somatic gonadal precursors after embryonic gonad coalescence to investigate molecular mechanisms involved in the setting up and regulation of the germline program. Profiling of the early germline chromatin landscape revealed sex- and stage-specific features. In the male germline immediately after zygotic activation, the chromatin structure underwent a brief remodeling phase during which nucleosome density was lower and deconcentrated from promoter regions. These findings echoed enrichment analysis results of our genomics data in which top candidates were factors with the ability to mediate large-scale chromatin reorganization. Together, they point to the importance of chromatin regulation in the early germline and raise the possibility of a conserved epigenetic reprogramming-like process required for proper initiation of germline development.

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