The histone chaperone function of Daxx is dispensable for embryonic development

Area of Science:

• Epigenetics and Gene Regulation
• Molecular Biology
• Developmental Biology

Background:

• Daxx is a histone chaperone essential for embryonic development.
• Daxx forms a complex with Atrx to deposit histone H3.3 into heterochromatin.
• Understanding Daxx's in vivo functions requires dissecting its interactions.

Purpose of the Study:

• To investigate the in vivo functions of Daxx by creating specific interaction mutants.
• To differentiate between Atrx-dependent and H3.3-dependent functions of Daxx.
• To elucidate the role of Daxx in epigenetic regulation and genome stability.

Main Methods:

• Generation of two mouse Daxx mutant alleles: Daxx^Y130A (abolishing Daxx-Atrx interaction) and Daxx^S226A (abolishing Daxx-H3.3 interaction).
• Viability and fertility assessment of mutant mice.
• Transcriptome analysis of embryonic tissues to evaluate gene expression changes.
• Analysis of endogenous retroviral expression and immune cell composition.

Main Results:

• Mice with abolished Daxx-Atrx interaction (Daxx^Y130A) are viable and fertile but show dysregulated endogenous retroviral expression.
• Mice with abolished Daxx-H3.3 interaction (Daxx^S226A) are essential for postnatal viability, indicating a critical role in development beyond embryogenesis.
• The Daxx-H3.3 interaction is crucial for silencing endogenous retroviruses and maintaining proper immune cell composition.

Conclusions:

• Daxx exhibits both Atrx-dependent and independent functions in vivo.
• The Daxx-Atrx interaction is dispensable for viability but influences retroviral silencing.
• The Daxx-H3.3 interaction is vital for postnatal survival, retroviral silencing, and immune homeostasis, highlighting distinct roles in epigenetic regulation.