DNA polymerase δ is required for early mammalian embryogenesis

Abstract

Background: In eukaryotic cells, DNA polymerase δ (Polδ), whose catalytic subunit p125 is encoded in the Pold1 gene, plays a central role in chromosomal DNA replication, repair, and recombination. However, the physiological role of the Polδ in mammalian development has not been thoroughly investigated. Methodology/Principal Findings: To examine this role, we used a gene targeting strategy to generate two kinds of Pold1 mutant mice: Polδ-null (Pold1-/-) mice and D400A exchanged Polδ (Pold1exo/exo) mice. The D400A exchange caused deficient 3′-5′ exonuclease activity in the Polδ protein. In Polδ-null mice, heterozygous mice developed normally despite a reduction in Pold1 protein quantity. In contrast, homozygous Pold1-/- mice suffered from peri-implantation lethality. Although Pold1-/- blastocysts appeared normal, their in vitro culture showed defects in outgrowth proliferation and DNA synthesis and frequent spontaneous apoptosis, indicating Polδ participates in DNA replication during mouse embryogenesis. In Pold1exo/exo mice, although heterozygous Pold1exo/+ mice were normal and healthy, Pold1exo/exo and Pold1exo/- mice suffered from tumorigenesis. Conclusions: These results clearly demonstrate that DNA polymerase δ is essential for mammalian early embryogenesis and that the 3′-5′ exonuclease activity of DNA polymerase d is dispensable for normal development but necessary to suppress tumorigenesis. © 2009 Uchimura et al.