The Effect of DNA Repair Defects on Reproductive Performance in Nucleotide Excision Repair (NER) Mouse Models: An Epidemiological Approach

DNA damage shifts circadian clock time via Hausp-dependent Cry1 stabilization

The circadian transcriptional repressors cryptochrome 1 (Cry1) and 2 (Cry2) evolved from photolyases, bacterial light-activated DNA repair enzymes. In this study, we report that while they have lost DNA repair activity, Cry1/2 adapted to protect genomic integrity by responding to DNA damage through posttranslational modification and coordinating the downstream transcriptional response. We demonstrate that genotoxic stress stimulates Cry1 phosphorylation and its deubiquitination by Herpes virus associated ubiquitin-specific protease (Hausp, a.k.a Usp7), stabilizing Cry1 and shifting circadian clock time. DNA damage also increases Cry2 interaction with Fbxl3, destabilizing Cry2. Thus, genotoxic stress increases the Cry1/Cry2 ratio, suggesting distinct functions for Cry1 and Cry2 following DNA damage. Indeed, the transcriptional response to genotoxic stress is enhanced in Cry1-/- and blunted in Cry2-/- cells. Furthermore, Cry2-/- cells accumulate damaged DNA. These results suggest that Cry1 and Cry2, which evolved from DNA repair enzymes, protect genomic integrity via coordinated transcriptional regulation.

XPC gene polymorphisms and risk of idiopathic azoospermia or oligozoospermia in a Chinese population

A retrospective case-control study was carried out in the Han-Chinese population to determine the polymorphisms of xeroderma pigmentosum complementation group C (XPC) gene on the risk of idiopathic azoospermia or oligozoospermia. The Ala499Val (C>T) and Lys939Gln (A>C) polymorphism of XPC gene were genotyped by polymerase chain reaction-restriction fragment length polymorphism in three groups of infertile men (172 patients of azoospermia, 25 patients of severe oligozoospermia, 55 patients of oligozoospermia) and 228 fertile men. Increased risk of idiopathic azoospermia, but not oligozoospermia was associated with the XPC variant genotypes of Ala499Val (C>T) [adjusted odds ratio (OR) = 1.67, 95% confidence interval (CI) = 1.04-2.68 for CT heterozygote and adjusted OR = 2.03, 95% CI = 1.10-3.75 for TT homozygote] compared with CC homozygous wide-type. The Lys939Gln (A>C) polymorphism was not related to spermatogenic failure. The combined risk alleles analysis and haplotype analysis showed that ORs increased as the number of the risk alleles increased and the 499T-939C haplotype had a significantly increased risk of idiopathic azoospermia (OR = 7.97; 95% CI = 3.51-18.07) compared with other haplotypes. The results suggest that XPC Ala499Val (C>T) polymorphism is correlated with high risk of idiopathic azoospermia in the Han-Chinese population.

Do heat stress and deficits in DNA repair pathways have a negative impact on male fertility?

In Europe up to one in four couples experience difficulty conceiving and in half of these cases the problem has been attributed to sub or infertility in the male partner. The development of assisted reproductive technologies (ART) such as in vitro fertilization and intra-cytoplasmic spermatozoa injection has allowed some such couples to achieve a pregnancy. Concerns have been raised over the increasing use of ART not least because of the discovery of elevated levels of DNA damage in sperm from subfertile men. The impact of damaged DNA originating in the male germ line is poorly understood, but is thought to contribute to early pregnancy loss (recurrent miscarriage), placental problems and have a long-term impact on the health of the offspring. DNA repair is essential for meiotic recombination and correction of DNA damage in germ cells and proteins involved in all the major repair pathways are expressed in the testis. In this review, we will consider evidence that the production of sperm containing damaged DNA can be the result of suboptimal DNA repair and/or a mild environmental insult, such as heat stress, and how studies in mice may give us insight into the origins and consequences of DNA damage in human sperm.