Rad18 is required for long-term maintenance of spermatogenesis in mouse testes

Abstract

Maintaining the integrity of spermatogenic stem cells is essential to transfer genetic information to a descendant. However, knowledge of maintenance of genetic stability in stem cells is still limited. RAD18 is critical for postreplication repair through mono- and multi-ubiquitination of proliferating cell nuclear antigen (PCNA) to maintain genomic stability. Mammalian RAD18 is highly expressed in the spermatocytes and the nuclei of a few spermatogonia in adult mice. To elucidate the physiological function of RAD18, we analyzed a phenotype of Rad18-/- mice. The mice were born and appeared to grow normally. Although the mice were fertile, fertility and testis weight decreased with age. Histological examination revealed normal spermatogenesis in almost all seminiferous tubules in Rad18-/- testes at 2 months old, and abnormal sperm could not be detected in the epididymis. However, 25% of the tubules lost almost all germ cells at 12 months. The seminiferous tubules frequently retained only late differentiated phase germ cells, suggesting that the exhaustion of spermatogonial stem cells leads to the loss of all germ cells in the seminiferous tubules. Wild-type germ cells were successfully transplanted into and colonized in the seminiferous tubules of aged Rad18-/- mice, indicating that Sertoli cells have a normal supportive function even in aged testes. We conclude that RAD18 is intrinsically required for the long-term maintenance of spermatogenesis.

Genetic Deficiency of Mtdh Gene in Mice Causes Male Infertility via Impaired Spermatogenesis and Alterations in the Expression of Small Non-coding RNAs

“…In contrast to spermatocytes, some Brca2-deficient oocytes can progress through meiotic prophase I and can be fertilized to produce embryos. Deficiency of Rad18 is also associated with impaired spermatogenesis (29). Further confirming a role for MTDH in DNA damage repair, we observed increased Rad18 foci in the lumina of the seminiferous tubules in testes from Mtdh exon 3-depleted mice, and some punctate staining that did not co-localize with the Y chromosome.…”

“…Second, as with previously reported knock-out mouse models targeting other classic, general DNA repair molecules, Mtdh deficiency using our strategy results in male sterility. For example, deficiency of Atm, Brca2, and Rad18 similarly results in defects in spermatogenesis (29,(37)(38)(39). ATM, the gene mutated in the human autosomal recessive disorder ataxia telangiectasia, plays a crucial role in the detection of DSBs and is a signal transduction protein in the DNA damage surveillance network.…”

CHFR is important for the survival of male premeiotic germ cells

“…[14][15][16][17] Since spermatogonial stem cells give rise to all germ cells and pass the genetic information to the offspring, it is essential that genomic integrity is carefully maintained in these cells, which requires robust DNA damage response. 21 When certain DNA damage response fails to repair the DNA lesions, apoptosis is activated to eliminate the cells to prevent the damaged or mutated DNA to be passed on to the offspring.…”

“…Absence of these proteins leads to depletion of spermatogonial stem cells pool and complete loss of germ cells in testes and causes azoospermia in adult mice. [14][15][16][17] CHFR is an E3 ubiquitin ligase and participates in DNA damage response. 18,19 It is recruited to DNA damage sites by poly(ADP-ribose) and is important for the first wave of protein ubiquitination there.…”

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

“…Some experiments using genetically modified mice indicate the importance of the DNA repair system for germ cell maintenance. Disruption of mouse Rad18, which is the main regulator of DNA damage tolerance, causes progressive loss of germ cells in the testis after 6 months postnatally, indicating its requirement for long-term maintenance of germ cells (55). Deficient expression of genes involved in nucleotide excision repair, such as HR23B, Ercc1, and Xpa, also impairs normal spermatogenesis and oogenesis in mice (56 -58).…”