Mutagenesis and human genetic disease: an introduction

Treatment of male infertility

Major difficulties exist in the accurate and meaningful diagnosis of male reproductive dysfunction, and our understanding of the epidemiology and etiology of male infertility has proven quite complex.The numerous spermatozoa produced in mammals and other species provides some degree of protection against adverse environmental conditions represented by physical and chemical factors that can reduce reproductive function and increase gonadal damage even resulting in testicular cancer or congenital malformations. The wide fluctuations of sperm production in men, both geographical and temporal, may reflect disparate environmental exposures, occurring on differing genetic backgrounds, in varying psychosocial conditions, and leading to the diversified observed outcomes.Sperm analysis is still the cornerstone in diagnosis of male factor infertility, indeed, individually compromised semen paramaters while adequately address therapeutic practices is progressively flanked by additional tests. Administration of drugs, IUI, correction of varicocele, and, to a certain extent, IVF although they may not be capable of restoring fertility itself often result in childbearing.

The physico-chemical "anatomy" of the tautomerization through the DPT of the biologically important pairs of hypoxanthine with DNA bases: QM and QTAIM perspectives

The biologically important tautomerization of the Hyp·Cyt, Hyp·Thy and Hyp·Hyp base pairs to the Hyp·Cyt, Hyp·Thy and Hyp·Hyp base pairs, respectively, by the double proton transfer (DPT) was comprehensively studied in vacuo and in the continuum with a low dielectric constant (ε = 4) corresponding to hydrophobic interfaces of protein-nucleic acid interactions by combining theoretical investigations at the B3LYP/6-311++G(d,p) level of QM theory with QTAIM topological analysis. Based on the sweeps of the energetic, electron-topological, geometric and polar parameters, which describe the course of the tautomerization along the intrinsic reaction coordinate (IRC), it was proved that the tautomerization through the DPT is concerted and asynchronous process for the Hyp·Cyt and Hyp·Thy base pairs, while concerted and synchronous for the Hyp·Hyp homodimer. The continuum with ε = 4 does not affect qualitatively the course of the tautomerization reaction for all studied complexes. The nine key points along the IRC of the Hyp·Cyt↔Hyp·Cyt and Hyp·Thy↔Hyp·Thy tautomerizations and the six key points of the Hyp·Hyp↔Hyp·Hyp tautomerization have been identified and fully characterized. These key points could be considered as electron-topological "fingerprints" of concerted asynchronous (for Hyp·Cyt and Hyp·Thy) or synchronous (for Hyp·Hyp) tautomerization process via the DPT. It was found, that in the Hyp·Cyt, Hyp·Thy, Hyp·Hyp and Hyp·Hyp base pairs all H-bonds are significantly cooperative and mutually reinforce each other, while the C2H…O2 H-bond in the Hyp·Cyt base pair and the O6H…O4 H-bond in the Hyp·Thy base pair behave anti-cooperatively, i.e., they become weakened, while two others become strengthened.

Whole genome sequencing for quantifying germline mutation frequency in humans and model species: cautious optimism

Factors affecting the type and frequency of germline mutations in animals are of significant interest from health and toxicology perspectives. However, studies in this field have been limited by the use of markers with low detection power or uncertain relevance to phenotype. Whole genome sequencing (WGS) is now a potential option to directly determine germline mutation type and frequency in family groups at all loci simultaneously. Medical studies have already capitalized on WGS to identify novel mutations in human families for clinical purposes, such as identifying candidate genes contributing to inherited conditions. However, WGS has not yet been used in any studies of vertebrates that aim to quantify changes in germline mutation frequency as a result of environmental factors. WGS is a promising tool for detecting mutation induction, but it is currently limited by several technical challenges. Perhaps the most pressing issue is sequencing error rates that are currently high in comparison to the intergenerational mutation frequency. Different platforms and depths of coverage currently result in a range of 10-10(3) false positives for every true mutation. In addition, the cost of WGS is still relatively high, particularly when comparing mutation frequencies among treatment groups with even moderate sample sizes. Despite these challenges, WGS offers the potential for unprecedented insight into germline mutation processes. Refinement of available tools and emergence of new technologies may be able to provide the improved accuracy and reduced costs necessary to make WGS viable in germline mutation studies in the very near future. To streamline studies, researchers may use multiple family triads per treatment group and sequence a targeted (reduced) portion of each genome with high (20-40 ×) depth of coverage. We are optimistic about the application of WGS for quantifying germline mutations, but caution researchers regarding the resource-intensive nature of the work using existing technology.

History of environmental and molecular mutagenesis

Environmental and Molecular Mutagenesis, the journal of the Environmental Mutagen Society (EMS), marks its 25th anniversary in 2004. The journal, originally called Environmental Mutagenesis, was established in 1979 with Seymour Abrahamson as its first editor. The development of the journal is closely linked to the evolution of the fields of mutation research and genetic toxicology. This perspective traces the founding of the journal and discusses its editorial history, growth, content, style, administration, and relationship to the EMS.

Life cycle of the mammalian germ cell: implication for spontaneous mutation frequencies

A brief history of the developmental life cycle of the mammalian germ cell, from fertilization to gametogenesis in the mature gonad, is presented. The differences between gametogenesis in the mature gonad of males and females are also described with regard to properties that may affect their susceptibilities to mutation. It is emphasized that any historical control background rate of necessity will include mutations that occur in germinal tissue at all stages of development and differentiation, although it is not always possible to determine at what stage of germline development a spontaneous mutation has occurred. Studies of induced mutations suggest that the impact on the molecular level and the distribution of mutations among the F1 and F2 progeny may be partly determined by the stage and sex of germ cells in which spontaneous mutations occur. In summary, historical control rates should only be considered the sum total of mutations that occur during the entire life of the individual and cannot represent the control values of any individual germ cell stage. Nonetheless, it is certainly important and valid to use historical control data for calculating human risk, because the primary use of the estimation of mutant frequencies is to access the potential impact of agents in increasing the genetic load in the human population.

Genetic activity profiles of anticancer drugs

The results from short-term tests for genetic and related effects, abstracted from the open literature for 36 anticancer drugs, are examined in this review. Data for 27 of these agents are available in the EPA/IARC Genetic Activity Profile (GAP) database. Data summaries, including data listings and activity profiles, are presented for nine anticancer drugs added to the GAP database for this analysis. Genetic toxicity data from the recent literature are included for the additional agents to provide a broader representation of the categories of drugs being evaluated. These categories, based on the chemical mode of action, are covalent and noncovalent DNA-binding drugs, topoisomerase II inhibitors, antimetabolites, mitotic spindle inhibitors, and drugs which affect endocrine function. The qualitative data for all 36 drugs are summarized in this report and findings are presented from pair-wise matching of genetic activity profiles, based on test results in common, for some chemical analogs. The significance of germ cell test results for some of these drugs and their implication in assessing risk of heritable genetic disease are discussed.