The REV7 Subunit of DNA Polymerase ζ Is Essential for Primordial Germ Cell Maintenance in the Mouse

Naoki Watanabe,Shinji Mii,Naoya Asai,Masato Asai,Kaoru Niimi,Kaori Ushida,Takuya Kato,Atsushi Enomoto,Hideshi Ishii,Masahide Takahashi,Yoshiki Murakumo

doi:10.1074/jbc.m112.421966

Abstract

REV7 (also known as MAD2L2 and MAD2B) is involved in DNA repair, cell cycle regulation, gene expression, and carcinogenesis. In vitro studies show that REV7 interacts with several proteins and regulates their function. It has been reported that human REV7 is highly expressed in the adult testis by Northern blot analysis. However, the significance of REV7 in mammalian development has not been elucidated. Here, we present analyses of REV7-deficient (Rev7(-/-)) mice to clarify the significance of Rev7 in mouse development. In WT mice (Rev7(+/+)), Rev7 expression was ubiquitously observed in the embryo and confined to germ cells in the testes after birth. Rev7(-/-) mice exhibited growth retardation and a partial embryonic lethal phenotype. Mice that survived to adulthood were infertile in both sexes and showed germ cell aplasia in the testes and ovaries. Analyses of Rev7(-/-) embryos revealed that primordial germ cells (PGCs) were present at embryonic day 8.5 (E8.5). However, progressive loss of PGCs was observed during migration, and PGCs were absent in the genital ridges at E13.5. An increase of apoptotic cells was detected not only among PGCs but also in the forebrain of the Rev7(-/-) embryo, whereas cell proliferation was unaffected. Moreover, DNA damage accumulation and increased levels of histone methylation were detected in Rev7(-/-) embryos, and expression of Oct4 and Nanog was deregulated by REV7 deficiency at E8.5. These findings indicate that Rev7 is essential for PGC maintenance by prevention of apoptotic cell death in the mouse.

Highlights

Biological significance of REV7 in mouse development has not been elucidated
DNA damage accumulation and increased levels of histone methylation were detected in Rev7؊/؊ embryos, and expression of Oct4 and Nanog was deregulated by REV7 deficiency at E8.5
On the other hand, during newborn and young adult periods, REV7 expression was clearly detected in the testis at all ages, whereas REV7 gradually diminished with age in other organs analyzed by Western blotting (Fig. 2G). These results indicate that REV7 is expressed in a wide range of cells during embryonic stages and its expression subsequently becomes confined to the testis after birth

Summary

Background

Biological significance of REV7 in mouse development has not been elucidated. Results: REV7-deficient mice show germ cell aplasia at birth in both sexes, and primordial germ cells (PGCs) were lost because of apoptosis during migration at an early embryonic stage. DNA damage accumulation and increased levels of histone methylation were detected in Rev7؊/؊ embryos, and expression of Oct and Nanog was deregulated by REV7 deficiency at E8.5 These findings indicate that Rev is essential for PGC maintenance by prevention of apoptotic cell death in the mouse. IpaB-bound REV7 is sequestered away from CDH1, causing unscheduled activation of the anaphase-promoting complex, which disrupts cell cycle-dependent regulation of cyclin B1 expression, resulting in cell cycle arrest at the G2/M phase in Shigella-infected epithelial cells These findings indicate that REV7 is involved in cell cycle regulation. Our findings indicate the importance of REV7 expression in mouse development

EXPERIMENTAL PROCEDURES

RESULTS

DISCUSSION