Gender differences in the induction of chromosomal aberrations and gene mutations in rodent germ cells

A perspective on the developmental toxicity of inhaled nanoparticles

This paper aimed to clarify whether maternal inhalation of engineered nanoparticles (NP) may constitute a hazard to pregnancy and fetal development, primarily based on experimental animal studies of NP and air pollution particles. Overall, it is plausible that NP may translocate from the respiratory tract to the placenta and fetus, but also that adverse effects may occur secondarily to maternal inflammatory responses. The limited database describes several organ systems in the offspring to be potentially sensitive to maternal inhalation of particles, but large uncertainties exist about the implications for embryo-fetal development and health later in life. Clearly, the potential for hazard remains to be characterized. Considering the increased production and application of nanomaterials and related consumer products a testing strategy for NP should be established. Due to large gaps in data, significant amounts of groundwork are warranted for a testing strategy to be established on a sound scientific basis.

In utero exposure to nanosized carbon black (Printex90) does not induce tandem repeat mutations in female murine germ cells

Inhalation of particles has been shown to induce mutations in the male germline in mice following both prenatal and adult exposures in several experiments. In contrast, the effects of particles on female germ cell mutagenesis are not well established. Germline mutations are induced during active cell division, which occurs during fetal development in females. We investigated the effects of prenatal exposure to carbon black nanoparticles (CB) on induction of mutations in the female mouse germline during fetal development, spanning the critical developmental stages of oogenesis. Pregnant C57BL/6J mice were exposed four times during gestation by intratracheal instillation of 67μg/animal of nanosized carbon black Printex90 or vehicle (gestation days 7, 10, 15 and 18). Female offspring were raised to maturity and mated with unexposed CBA males. Expanded simple tandem repeat (ESTR) germline mutation rates in the resulting F2 generation were determined from full pedigrees (mother, father, offspring) of F1 female mice (178 CB-exposed and 258 control F2 offspring). ESTR mutation rates in CB-exposed F2 female offspring were not statistically different from those of F2 female control offspring.

Male-mediated infertility in sons of building painters and gardeners: a nationwide register-based follow-up study

AIM

To investigate whether sons of gardeners and building painters have increased risk of infertility in comparison with sons of bricklayers, carpenters and electricians.

METHODS

Participants were men born 1965-1984 in Denmark whose fathers the year before birth had worked as gardeners, painters, bricklayers, carpenters or electricians (N=22,978). Cases of infertility were identified by Danish registers, and participants were followed-up for up to 24 years after their 20th birthday.

RESULTS

Sons of gardeners did not have increased risk of infertility. Hazard ratios for sons of painters fluctuated around the null in main analyses but were 1.6 (98% CI: 1.0-2.5) and 1.7 (95% CI: 0.9-3.2) in the subset of participants with smallest risk of paternal exposure misclassification.

CONCLUSIONS

Working as gardener or building painter was not related to increased risk of infertility among the next generation of males in main analyses. However, inherent limitations in data may have attenuated true associations.

Radiobiology and reproduction-what can we learn from Mammalian females?

Ionizing radiation damages DNA and induces mutations as well as chromosomal reorganizations. Although radiotherapy increases survival among cancer patients, this treatment does not come without secondary effects, among which the most problematic is gonadal dysfunction, especially in women. Even more, if radio-induced DNA damage occurs in germ cells during spermatogenesis and/or oogenesis, they can produce chromosomal reorganizations associated with meiosis malfunction, abortions, as well as hereditary effects. However, most of our current knowledge of ionizing radiation genotoxic effects is derived from in vitro studies performed in somatic cells and there are only some experimental data that shed light on how germ cells work when affected by DNA alterations produced by ionizing radiation. In addition, these few data are often related to mammalian males, making it difficult to extrapolate the results to females. Here, we review the current knowledge of radiobiology and reproduction, paying attention to mammalian females. In order to do that, we will navigate across the female meiotic/reproductive cycle/life taking into account the radiation-induced genotoxic effects analysis and animal models used, published in recent decades.

NanoTIO(2) (UV-Titan) does not induce ESTR mutations in the germline of prenatally exposed female mice

Background

Particulate air pollution has been linked to an increased risk of cardiovascular disease and cancer. Animal studies have shown that inhalation of air particulates induces mutations in the male germline. Expanded simple tandem repeat (ESTR) loci in mice are sensitive markers of mutagenic effects on male germ cells resulting from environmental exposures; however, female germ cells have received little attention. Oocytes may be vulnerable during stages of active cell division (e.g., during fetal development). Accordingly, an increase in germline ESTR mutations in female mice prenatally exposed to radiation has previously been reported. Here we investigate the effects of nanoparticles on the female germline. Since pulmonary exposure to nanosized titanium dioxide (nanoTiO₂) produces a long-lasting inflammatory response in mice, it was chosen for the present study.

Findings

Pregnant C57BL/6 mice were exposed by whole-body inhalation to the nanoTiO₂ UV-Titan L181 (~42.4 mg UV-Titan/m³) or filtered clean air on gestation days (GD) 8–18. Female C57BL/6 F1 offspring were raised to maturity and mated with unexposed CBA males. The F2 descendents were collected and ESTR germline mutation rates in this generation were estimated from full pedigrees (mother, father, offspring) of F1 female mice (192 UV-Titan-exposed F2 offspring and 164 F2 controls). ESTR mutation rates of 0.029 (maternal allele) and 0.047 (paternal allele) in UV-Titan-exposed F2 offspring were not statistically different from those of F2 controls: 0.037 (maternal allele) and 0.061 (paternal allele).

Conclusions

We found no evidence for increased ESTR mutation rates in F1 females exposed in utero to UV-Titan nanoparticles from GD8-18 relative to control females.

Sex-gender research sensitivity and healthcare disparities

Authors Nieuwenhoven and Klinge (Journal of Women's Health 2010;19:1-6) argue that despite advances, sex and gender are not well treated in the biomedical literature. Many studies in which males and females are represented do not address the similarities or differences between sexes, sometimes adjusting for (thereby obscuring) sex differences and sometimes ignoring sex altogether. Women continue to be underrepresented in randomized drug trials, excluded from some by potential reproductive effects, and perhaps frightened from others by IRB-required warnings. Although recognized, sex disparities in treatment, for example, for acute cardiac syndrome, persist. As electronic abstracts become a prime means of communicating research results, they must adequately and accurately represent a study's findings.

MCAK is present at centromeres, midspindle and chiasmata and involved in silencing of the spindle assembly checkpoint in mammalian oocytes

Mitotic centromere-associated kinesin (MCAK) is an ATP-dependent microtubule (MT) depolymerase regulated by Aurora kinase (AURK) phosphorylation and implicated in resolution of improper MT attachments in mitosis. Distribution of MCAK was studied in oocyte maturation by anti-MCAK antibody, anti-tubulin antibody, anti-AURKB antibody and anti-centromere antibody (ACA) and by the expression of MCAK-enhanced green fluorescent protein fusion protein in maturing mouse oocytes. Function was assessed by knockdown of MCAK and Mad2, by inhibiting AURK or the proteasome, by live imaging with polarization microscope and by chromosomal analysis. The results show that MCAK is transiently recruited to the nucleus and transits to spindle poles, ACA-positive domains and chiasmata at prometaphase I. At metaphase I and II, it is present at centrosomes and centromeres next to AURKB and checkpoint proteins Mad2 and BubR1. It is retained at centromeres at telophase I and also at the midbody. Knockdown of MCAK causes a delay in chromosome congression but does not prevent bipolar spindle assembly. MCAK knockdown also induces a meiosis I arrest, which is overcome by knockdown of Mad2 resulting in chiasma resolution, chromosome separation, formation of aberrant meiosis II spindles and increased hypoploidy. In conclusion, MCAK appears to possess a unique distribution and function in oocyte maturation. It is required for meiotic progression from meiosis I to meiosis II associated with silencing of the spindle assembly checkpoint. Alterations in abundance and activity of MCAK, as implicated in aged oocytes, may therefore contribute to the loss of control of cell cycle and chromosome behaviour, thus increasing risk for errors in chromosome segregation and aneuploidy.

Hazardous effect of tannery solid waste leachates on development and reproduction in Drosophila melanogaster: 70kDa heat shock protein as a marker of cellular damage

Rapid industrialization has increased the burden of chemicals in the environment. These chemicals may be harmful to development and reproduction of any organism. We therefore analyzed the adverse effects of leachates from a tannery solid waste on development and reproduction using Drosophila. We show a significant delay in mean emergence of flies observed at the higher concentrations of the leachates, indicating their effect on the organism's development. Significant leachate-induced effect on reproduction of the organism was also observed. Sub-organismal analyses revealed Hsp70 expression and tissue damage in a sex-specific manner. Refractoriness of Hsp70 expression in accessory glands of male flies and ovaries of females was concurrent with tissue damage. Genes encoding certain seminal proteins (Acp70A and Acp36DE) from accessory glands were significantly down-regulated at higher concentrations of the leachates. The study suggests that (i) sub-organismal adverse responses are reflected at organismal level, (ii) tannery waste leachates cause adverse effects on the expression of genes encoding seminal proteins that facilitate normal reproduction and (iii) Hsp70 may be used as a marker of cellular damage for reproductive organs.

Spindle formation, chromosome segregation and the spindle checkpoint in mammalian oocytes and susceptibility to meiotic error

The spindle assembly checkpoint (SAC) monitors attachment to microtubules and tension on chromosomes in mitosis and meiosis. It represents a surveillance mechanism that halts cells in M-phase in the presence of unattached chromosomes, associated with accumulation of checkpoint components, in particular, Mad2, at the kinetochores. A complex between the anaphase promoting factor/cylosome (APC/C), its accessory protein Cdc20 and proteins of the SAC renders APC/C inactive, usually until all chromosomes are properly assembled at the spindle equator (chromosome congression) and under tension from spindle fibres. Upon release from the SAC the APC/C can target proteins like cyclin B and securin for degradation by the proteasome. Securin degradation causes activation of separase proteolytic enzyme, and in mitosis cleavage of cohesin proteins at the centromeres and arms of sister chromatids. In meiosis I only the cohesin proteins at the sister chromatid arms are cleaved. This requires meiosis specific components and tight regulation by kinase and phosphatase activities. There is no S-phase between meiotic divisions. Second meiosis resembles mitosis. Mammalian oocytes arrest constitutively at metaphase II in presence of aligned chromosomes, which is due to the activity of the cytostatic factor (CSF). The SAC has been identified in spermatogenesis and oogenesis, but gender-differences may contribute to sex-specific differential responses to aneugens. The age-related reduction in expression of components of the SAC in mammalian oocytes may act synergistically with spindle and other cell organelles' dysfunction, and a partial loss of cohesion between sister chromatids to predispose oocytes to errors in chromosome segregation. This might affect dose-response to aneugens. In view of the tendency to have children at advanced maternal ages it appears relevant to pursue studies on consequences of ageing on the susceptibility of human oocytes to the induction of meiotic error by aneugens and establish models to assess risks to human health by environmental exposures.

Adverse effect of organophosphate compounds, dichlorvos and chlorpyrifos in the reproductive tissues of transgenic Drosophila melanogaster: 70kDa heat shock protein as a marker of cellular damage

The study highlights the adverse effects of organophosphate compounds dichlorvos and chlorpyrifos on reproduction in Drosophila. Freshly eclosed first instar larvae of Drosophila melanogaster transgenic for hsp70 (hsp70-lacZ) Bg(9) were fed on 0.015-150.0ppb dichlorvos and chlorpyrifos mixed food. Virgin flies eclosing from the normal and contaminated food were pair-mated to examine the effect of the test chemicals on reproduction of the exposed organisms. Expression of hsp70, sex peptide (SP or Acp70A), accessory gland protein (Acp36DE) and tissue damage was examined in reproductive organs of adult fly. Exposed organisms exhibited a dose-dependent significantly reduced reproductive outcome and males were found to be more sensitive than females. Hsp70 expression was restricted only within the testis lobes of male fly while it was not induced in the ovary of the female. In concurrence with absence of hsp70 expression in the accessory glands of male fly, tissue damage was evident in them. Acp70A and Acp36DE expression were found to be significantly downregulated at the higher concentrations of the test chemicals. The study suggests that (i) dichlorvos is more deleterious to fly reproduction compared to chlorpyrifos with an adverse effect on Acp70A and Acp36DE expression required to facilitate normal reproduction; (ii) hsp70 may be used as a marker of cellular damage against dichlorvos and chlorpyrifos in Drosophila.