Supraphysiological protection from replication stress does not extend mammalian lifespan

Area of Science:

• Molecular Biology
• Genetics
• Aging Research

Background:

• Replication stress (RS) involves DNA damage and single-stranded DNA accumulation.
• Elevated RS is observed in aged cells, and RS response deficiency accelerates aging in mice.
• The role of physiological RS in normal aging remains unclear.

Purpose of the Study:

• To investigate the impact of enhanced replication stress (RS) protection on lifespan in physiological aging.
• To determine if supraphysiological RS mitigation extends longevity in normal aging contexts.

Main Methods:

• Long-term survival studies were conducted on transgenic mice overexpressing Chk1 and/or Rrm2 genes.
• These genes were previously shown to extend lifespan in a progeroid model with high RS.
• Comparison of lifespan and tumor incidence between transgenic mice and wild-type (WT) littermates.

Main Results:

• Transgenic mice (Chk1, Rrm2, and Chk1/Rrm2) exhibited lifespans similar to WT littermates under physiological conditions.
• The primary cause of death in most mice, regardless of genetic background, was tumor development (mainly lymphomas).
• A trend towards higher tumor incidence was observed in transgenic mice, though not statistically significant.

Conclusions:

• Enhanced protection against replication stress (RS) does not prolong lifespan in normal aging.
• Replication stress may not be a significant contributor to the genomic instability driving normal aging.
• Tumorigenesis, rather than RS, appears to be a major factor limiting lifespan in these models.