Dynamics of histone acetylation during human early embryogenesis

Area of Science:

• Epigenetics
• Developmental Biology
• Genomics

Background:

• Regulation of gene and transposon transcription in early human embryogenesis is poorly understood.
• Histone modifications play crucial roles in embryonic development.

Purpose of the Study:

• To investigate the role and regulation of histone acetylation, specifically H3K27ac, during human early embryogenesis.
• To understand the association of H3K27ac with gene and transposon expression before and after zygotic genome activation (ZGA).

Main Methods:

• Chromatin immunoprecipitation (ChIP) followed by sequencing to map H3K27ac and H3K4me3 domains.
• Analysis of histone deacetylase and P300 function.
• Comparative analysis with mouse embryos.

Main Results:

• Broad H3K27ac domains are present in early human embryos (2-cell, 4-cell) and transition to typical peaks by the 8-cell stage, a pattern conserved in mice before ZGA.
• Histone deacetylases are essential for the removal of broad H3K27ac domains and for ZGA.
• P300 is critical for establishing H3K27ac peaks and gene expression post-ZGA.
• H3K27ac marks active transposons, with distinct roles for different histone acetylations (H3K27ac, H3K18ac, H3K9ac) in transposon activation.

Conclusions:

• H3K27ac undergoes significant reprogramming during mammalian early embryonic development.
• This reprogramming is linked to the stage-specific expression of both genes and transposons.
• Epigenetic regulation by histone acetylation is crucial for mammalian embryogenesis and genome regulation.