H3K9 post-translational modifications regulate epiblast/primitive endoderm specification in rabbit blastocysts.

Area of Science:

• Epigenetics
• Developmental Biology
• Mammalian Embryogenesis

Background:

• Post-translational modifications of histone H3 on lysine 9, including acetylation (H3K9ac) and tri-methylation (H3K9me3), are key regulators of chromatin accessibility.
• The specific roles of these histone modifications in mammalian blastocyst lineage segregation are not well understood.

Purpose of the Study:

• To investigate the dynamic changes and functional significance of histone H3 lysine 9 modifications during rabbit blastocyst development.
• To elucidate the involvement of H3K9ac, H3K9me2, and H3K9me3 in the segregation of inner cell mass lineages.

Main Methods:

• Quantitative analysis of H3K9ac, H3K9me2, and H3K9me3 levels during rabbit blastocyst cavitation and expansion.
• Pharmacological inhibition and enhancement of H3K9 methylation and acetylation pathways.
• Assessment of gene expression related to pluripotency and lineage determination.

Main Results:

• H3K9me2 and H3K9me3 levels decrease during rabbit blastocyst expansion, with H3K9me3 notably low in inner cell mass cells before increasing prior to gastrulation.
• H3K9ac is abundant in early blastocysts but diminishes during the inner cell mass to epiblast transition.
• Inhibition of H3K9me2/3 disrupts primitive endoderm segregation, while enhanced H3K9ac promotes epiblast expansion over primitive endoderm formation.

Conclusions:

• Dynamic changes in H3K9 methylation and acetylation are critical for regulating lineage segregation in the mammalian blastocyst.
• These epigenetic modifications influence the expression of genes involved in pluripotency and cell fate determination, highlighting their importance in embryonic development.