YY1-Mediated Polycomb Group Function Safeguards Hematopoietic Stem Cells from Premature Aging.

Area of Science:

• Epigenetics
• Stem Cell Biology
• Aging Research

Background:

• Hematopoietic stem cells (HSCs) decline functionally with age, showing myeloid bias and loss of quiescence.
• The molecular drivers of HSC aging are not fully understood.
• Yin Yang 1 (YY1) is a transcription factor involved in epigenetic regulation via Polycomb group (PcG) complexes.

Purpose of the Study:

• To investigate the role of YY1's Polycomb group (PcG) function in adult HSC aging.
• To define the epigenetic mechanisms underlying HSC functional decline.

Main Methods:

• Generated a conditional YY1 REPO domain knockout mouse model (Yy1-/ΔREPO).
• Analyzed HSC immunophenotype, self-renewal capacity, differentiation output, and cellular aging markers.
• Utilized RNA-sequencing (RNA-seq) to assess gene network dysregulation.

Main Results:

• Deletion of the YY1 REPO domain caused premature HSC aging and loss of long-term self-renewal.
• Yy1-/ΔREPO HSCs exhibited myeloid-biased differentiation, reduced quiescence, and increased oxidative stress.
• RNA-seq revealed dysregulated metabolic gene networks in aged HSCs.

Conclusions:

• YY1 PcG activity is essential for maintaining HSC metabolic quiescence and self-renewal capacity.
• YY1 PcG function acts as a key epigenetic regulator that delays HSC aging.
• This study reveals a fundamental PcG-dependent epigenetic mechanism controlling HSC fate and function during aging.