Male-driven de novo mutations in haploid germ cells (original) (raw)
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Meiotic recombination counteracts male-biased mutation (male-driven evolution)
Proceedings. Biological sciences / The Royal Society, 2016
Meiotic recombination is believed to produce greater genetic variation despite the fact that deoxyribonucleic acid (DNA)-replication errors are a major source of mutations. In some vertebrates, mutation rates are higher in males than in females, which developed the theory of male-driven evolution (male-biased mutation). However, there is little molecular evidence regarding the relationships between meiotic recombination and male-biased mutation. Here we tested the theory using the frog Rana rugosa, which has both XX/XY- and ZZ/ZW-type sex-determining systems within the species. The male-to-female mutation-rate ratio (α) was calculated from homologous sequences on the X/Y or Z/W sex chromosomes, which supported male-driven evolution. Surprisingly, each α value was notably higher in the XX/XY-type group than in the ZZ/ZW-type group, although α should have similar values within a species. Interestingly, meiotic recombination between homologous chromosomes did not occur except at termin...
DNA repair decline during mouse spermiogenesis results in the accumulation of heritable DNA damage
DNA Repair, 2008
The post-meiotic phase of mouse spermatogenesis (spermiogenesis) is very sensitive to the genomic effects of environmental mutagens because as male germ cells form mature sperm they progressively lose the ability to repair DNA damage. We hypothesized that repeated exposures to mutagens during this repair-deficient phase result in the accumulation of heritable genomic damage in mouse sperm that leads to chromosomal aberrations in zygotes after fertilization. We used a combination of single or fractionated exposures to diepoxybutane (DEB), a component of tobacco smoke, to investigate how differential DNA repair efficiencies during the three weeks of spermiogenesis affected the accumulation of DEB-induced heritable damage in early spermatids (21-15 days before fertilization, dbf), late spermatids (14-8 dbf) and sperm (7-1 dbf). Analysis of chromosomal aberrations in zygotic metaphases using PAINT/DAPI showed that late spermatids and sperm are unable to repair DEB-induced DNA damage as demonstrated by significant increases (P<0.001) in the frequencies of zygotes with chromosomal aberrations. Comparisons between single and fractionated exposures suggested that the DNA repair-deficient window during late spermiogenesis may be less than two weeks in the mouse and that during this repair-deficient window there is accumulation of DNA damage in sperm. Finally, the dose-response study in sperm indicated a linear response for both single and repeated exposures. These findings show that the differential DNA repair capacity of post-meioitic male germ cells has a major impact on the risk of paternally transmitted heritable damage and suggest that chronic exposures that may occur in the weeks prior to fertilization because of occupational or lifestyle factors (i.e, smoking) can lead to an accumulation of genetic damage in sperm and result in heritable chromosomal aberrations of paternal origin.
Genomic integrity in the male germ line: evidence in support of the disposable soma hypothesis
Reproduction (Cambridge, England), 2018
The Big Blue λ selection system has been employed along with whole-exome sequencing to examine the susceptibility of the male germ line to mutation in two challenging situations (i) exposure to a chemotherapeutic regime including bleomycin, etoposide and -platinum (BEP) and (ii) the ageing process. A 3-week exposure to BEP induced complete azoospermia associated with a loss of developing germ cells and extensive vacuolization of Sertoli cell cytoplasm. Following cessation of treatment, spermatozoa first appeared in the caput epididymis after 6 weeks and by 12 weeks motile spermatozoa could be recovered from the cauda, although the count ( < 0.001) and motility ( < 0.01) of these cells were significantly reduced and superoxide generation was significantly elevated ( < 0.001). Despite this increase in free radical generation, no evidence of chromatin instability was detected in these spermatozoa. Furthermore, embryos obtained from females mated at this 12-week time point show...
Origins and consequences of DNA damage in male germ cells
Reproductive BioMedicine Online, 2007
He moved to the University of Newcastle in 1998 from the University of Edinburgh, UK, where he held an Honorary Professorship in the Faculty of Medicine and a special appointment with the MRC Reproductive Biology Unit. His research interests are focused on the differentiation of male and female germ cells and the practical application of that knowledge in a clinical and biotechnology context.
AIMS Genetics, 2016
Male infertility is caused by many factors including genetics. Although part of genetic damages are inherited and could be traced in blood leukocytes, but those de novo alterations induced in spermatogenesis are not part of diagnostic work up. De novo alterations might be the cause of many idiopathic conditions of male infertility. The aim of this study was to evaluate DNA damage, sex chromosomal aneuploidy and DAZ microdeletion in sperms of subfertile males in comparison with normal healthy individuals. Whole blood and semen samples were obtained from 75 subfertile and 45 normal men. Semen samples from karyotypically normal subfertile and normal individuals were used for DNA fragmentation, sex chromosome aneuploidy and DAZ microdeletion analysis. Sperm DNA damage was assessed by alkaline comet assay, chromosome aneuploidy and DAZ microdeletion was assessed using a combined primed in situ labeling and fluorescent in situ hybridization (PRINS-FISH) method. A significantly high percentage of DNA fragmentation was observed in subfertile patients compared to control. Similar observation was observed for sex chromosome aneuploidy and DAZ microdeletion (p < 0.01). A relatively small interindividual difference was seen in all three assays performed. However DAZ microdeletion was observed as mosaic form in Y bearing sperms. Results indicate that subfertile males experience higher genome instability in spermatogenesis expressed as DNA damage and consequently sperm chromosomal 220 AIMS Genetics Volume 3, Issue 4, 219-238. aneuploidy or microdeletions. Occurrence of de novo genetic alterations caused by environmental chemico-physical genotoxic agents during spermatogenesis might be one of the causes of idiopathic male infertility.
New Male Studies, 2019
The function of the sexes is revealed within the context of new understanding that sex maintains genome integrity. Whereas originally evolved features of sex, conserved in early stages of meiosis, repair gross DNA damage, later phases repair fine-scale DNA damage (mutations) via ploidy and the sexes effecting purifying selection. Rather than in anisogamy, the (proto-)male arises in mating-types, revealing that greater selection on the male is the male's defining characteristic; this is confirmed in experiment and modelling. The variation theory ignores all evidence from many fields that it's asexual reproduction that produces variation. Recent tests unwittingly support the genome-integrity model. The profundity of male/female distinction in differential selection prompts new understanding of sociality and psychology in sex-specific terms.
Fertility and Sterility, 2010
Objective: To report a more quantitative approach to study the influence of varying levels of sperm DNA damage on transgenerational changes in genomic instability in a mouse model. Design: Experimental prospective study. Setting: Embryology research laboratory. Animal(s): Swiss albino mice. Intervention(s): The sperm DNA damage was induced by different doses of g-irradiation to male mice followed by mating with healthy female mice. Main Outcome Measure(s): Genomic integrity in embryos, fetus, and spermatozoa of F1 mice derived from the DNA-damaged sperm. Result(s): The transgenerational changes in genetic integrity were attributed by a dose-dependent increase in the frequency of micronuclei in preimplantation embryos and a concomitant increase in genomic instability in fetal liver cells and sperm chromatin modifications in F1 males. A strong positive correlation was observed between the extent of sperm DNA damage and somatic and germ-line genomic instability. Conclusion(s): Sperm-mediated transgenerational genomic instability is dependent on the amount of DNA damage present in the sire's sperm at the time of fertilization. (Fertil Steril Ò 2010;93:2486-90. Ó2010 by American Society for Reproductive Medicine.
The evolutionary role of recombinational repair and sex
International review of cytology, 1985
We have argued that sexual reproduction arose very early in the evolution of life as a way of overcoming informational damage or loss through recombinational repair. As organisms became more complex and genome information content expanded, diploidy, at first transient, became the predominant way of coping with increased vulnerability to mutation. This allowed further genome expansion. Once such expansion had occurred, however, diploidy became essentially irreversible, since reversion to haploidy would lead to expression of accumulated deleterious recessive alleles. This expression of recessive alleles also imposes a stiff penalty on organisms that experiment with close inbreeding forms of recombinational repair. A consequence of sex is that fitness (defined as per capita rate of increase) is density dependent. At low population density, fitness declines due to increased costs of finding a mate. This fundamental constraint on population increase can inhibit evolutionary success of th...