De novo point mutations and chromosomal structural aberrations (CSA) detected in offspring of unaffected parents show a preferential paternal origin with higher risk for older fathers. Studies in rodents suggest that heritable mutations transmitted from the father can arise from either paternal or maternal misrepair of damaged paternal DNA, and that the entire spermatogenic cycle can be at risk after mutagenic exposure. Understanding the susceptibility and mechanisms of transmission of paternal mutations is important in family planning after chemotherapy and donor selection for assisted reproduction. We report that treatment of male mice with melphalan (MLP), a bifunctional alkylating agent widely used in chemotherapy, induces DNA lesions during male mouse meiosis that persist unrepaired as germ cells progress through DNA repair-competent phases of spermatogenic development. After fertilization, unrepaired sperm DNA lesions are mis-repaired into CSA by the egg's DNA repair machinery producing chromosomally abnormal offspring. These findings highlight the importance of both pre- and post-fertilization DNA repair in assuring the genomic integrity of the conceptus.

This workshop reviewed the current science to inform and recommend the best evidence-based approaches on the use of germ cell genotoxicity tests. The workshop questions and key outcomes were as follows. (1) Do genotoxicity and mutagenicity assays in somatic cells predict germ cell effects? Limited data suggest that somatic cell tests detect most germ cell mutagens, but there are strong concerns that dictate caution in drawing conclusions. (2) Should germ cell tests be done, and when? If there is evidence that a chemical or its metabolite(s) will not reach target germ cells or gonadal tissue, it is not necessary to conduct germ cell tests, notwithstanding somatic outcomes. However, it was recommended that negative somatic cell mutagens with clear evidence for gonadal exposure and evidence of toxicity in germ cells could be considered for germ cell mutagenicity testing. For somatic mutagens that are known to reach the gonadal compartments and expose germ cells, the chemical could be assumed to be a germ cell mutagen without further testing. Nevertheless, germ cell mutagenicity testing would be needed for quantitative risk assessment. (3) What new assays should be implemented and how? There is an immediate need for research on the application of whole genome sequencing in heritable mutation analysis in humans and animals, and integration of germ cell assays with somatic cell genotoxicity tests. Focus should be on environmental exposures that can cause de novo mutations, particularly newly recognized types of genomic changes. Mutational events, which may occur by exposure of germ cells during embryonic development, should also be investigated. Finally, where there are indications of germ cell toxicity in repeat dose or reproductive toxicology tests, consideration should be given to leveraging those studies to inform of possible germ cell genotoxicity.

Environmental and Molecular MutagenesisVolume 54, Issue 2 p. 79-81 Commentary The development of adverse outcome pathways for mutagenic effects for the organization for economic co-operation and development Carole L. Yauk, Corresponding Author Carole L. Yauk carole.yauk@hc-sc.gc.ca Environmental Health Science and Research Bureau, Health Canada, Ottawa, Ontario, CanadaEnvironmental Health Science and Research Bureau, Health Canada, Ottawa, Ontario, CanadaSearch for more papers by this authorJack Bishop, Jack Bishop National Toxicology Program, National Institute of Environmental Health Sciences, Research Triangle Park, North CarolinaSearch for more papers by this authorKerry L. Dearfield, Kerry L. Dearfield United States Department of Agriculture, Food Safety and Inspection Service, Washington, District of ColumbiaSearch for more papers by this authorGeorge R. Douglas, George R. Douglas Environmental Health Science and Research Bureau, Health Canada, Ottawa, Ontario, CanadaSearch for more papers by this authorBarbara F. Hales, Barbara F. Hales Department of Pharmacology and Therapeutics, Department of Obstetrics and Gynecology, McGill University, Montreal, Quebec, CanadaSearch for more papers by this authorMirjam Luijten, Mirjam Luijten National Institute for Public Health and the Environment, Bilthoven, The NetherlandsSearch for more papers by this authorJason M. O'Brien, Jason M. O'Brien Environmental Health Science and Research Bureau, Health Canada, Ottawa, Ontario, CanadaSearch for more papers by this authorBernard Robaire, Bernard Robaire Department of Pharmacology and Therapeutics, Department of Obstetrics and Gynecology, McGill University, Montreal, Quebec, CanadaSearch for more papers by this authorRadim Sram, Radim Sram Institute of Experimental Medicine, Academy of Sciences of the Czech Republic, Prague, Czech RepublicSearch for more papers by this authorJan van Benthem, Jan van Benthem National Institute for Public Health and the Environment, Bilthoven, The NetherlandsSearch for more papers by this authorMike G. Wade, Mike G. Wade Environmental Health Science and Research Bureau, Health Canada, Ottawa, Ontario, CanadaSearch for more papers by this authorPaul A. White, Paul A. White Environmental Health Science and Research Bureau, Health Canada, Ottawa, Ontario, CanadaSearch for more papers by this authorFrancesco Marchetti, Francesco Marchetti Environmental Health Science and Research Bureau, Health Canada, Ottawa, Ontario, CanadaSearch for more papers by this author Carole L. Yauk, Corresponding Author Carole L. Yauk carole.yauk@hc-sc.gc.ca Environmental Health Science and Research Bureau, Health Canada, Ottawa, Ontario, CanadaEnvironmental Health Science and Research Bureau, Health Canada, Ottawa, Ontario, CanadaSearch for more papers by this authorJack Bishop, Jack Bishop National Toxicology Program, National Institute of Environmental Health Sciences, Research Triangle Park, North CarolinaSearch for more papers by this authorKerry L. Dearfield, Kerry L. Dearfield United States Department of Agriculture, Food Safety and Inspection Service, Washington, District of ColumbiaSearch for more papers by this authorGeorge R. Douglas, George R. Douglas Environmental Health Science and Research Bureau, Health Canada, Ottawa, Ontario, CanadaSearch for more papers by this authorBarbara F. Hales, Barbara F. Hales Department of Pharmacology and Therapeutics, Department of Obstetrics and Gynecology, McGill University, Montreal, Quebec, CanadaSearch for more papers by this authorMirjam Luijten, Mirjam Luijten National Institute for Public Health and the Environment, Bilthoven, The NetherlandsSearch for more papers by this authorJason M. O'Brien, Jason M. O'Brien Environmental Health Science and Research Bureau, Health Canada, Ottawa, Ontario, CanadaSearch for more papers by this authorBernard Robaire, Bernard Robaire Department of Pharmacology and Therapeutics, Department of Obstetrics and Gynecology, McGill University, Montreal, Quebec, CanadaSearch for more papers by this authorRadim Sram, Radim Sram Institute of Experimental Medicine, Academy of Sciences of the Czech Republic, Prague, Czech RepublicSearch for more papers by this authorJan van Benthem, Jan van Benthem National Institute for Public Health and the Environment, Bilthoven, The NetherlandsSearch for more papers by this authorMike G. Wade, Mike G. Wade Environmental Health Science and Research Bureau, Health Canada, Ottawa, Ontario, CanadaSearch for more papers by this authorPaul A. White, Paul A. White Environmental Health Science and Research Bureau, Health Canada, Ottawa, Ontario, CanadaSearch for more papers by this authorFrancesco Marchetti, Francesco Marchetti Environmental Health Science and Research Bureau, Health Canada, Ottawa, Ontario, CanadaSearch for more papers by this author First published: 28 January 2013 https://doi.org/10.1002/em.21757Citations: 16Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article.Citing Literature Volume54, Issue2March 2013Pages 79-81 RelatedInformation

Next-generation sequencing technologies can now be used to directly measure heritable de novo DNA sequence mutations in humans. However, these techniques have not been used to examine environmental factors that induce such mutations and their associated diseases. To address this issue, a working group on environmentally induced germline mutation analysis (ENIGMA) met in October 2011 to propose the necessary foundational studies, which include sequencing of parent–offspring trios from highly exposed human populations, and controlled dose–response experiments in animals. These studies will establish background levels of variability in germline mutation rates and identify environmental agents that influence these rates and heritable disease. Guidance for the types of exposures to examine come from rodent studies that have identified agents such as cancer chemotherapeutic drugs, ionizing radiation, cigarette smoke, and air pollution as germ-cell mutagens. Research is urgently needed to establish the health consequences of parental exposures on subsequent generations.

Deriving No Observed Adverse Effect Level (NOAEL) or benchmark dose is important for risk assessment and can be influenced by study design considerations. In order to define the di-(2-ethylhexyl) phthalate (DEHP) dose-response curve for reproductive malformations, we retained more offspring to adulthood to improve detection of these malformations in the reproductive assessment by continuous breeding study design. Sprague-Dawley rats were given a dietary administration of 1.5 (control), 10, 30, 100, 300, 1000, 7500, and 10,000 ppm DEHP. Male pups were evaluated for gross reproductive tract malformations (RTMs) associated with the "phthalate syndrome." DEHP treatment had minimal effects on P0 males. There was a statistically significant increase in F1 and F2 total RTMs (testis, epididymides, seminal vesicle, and prostate) in the 7500-ppm dose group and F1 10,000-ppm dose group. The 10,000-ppm exposed F1 males did not produce an F2 generation. The NOAEL for F1 and F2 RTM combined data, because in utero exposures were similar, were 100 ppm (4.8 mg/kg/day), which was close to the 5% response benchmark dose lower confidence limit of 142 ppm. The utility of evaluating more pups per litter was examined by generating power curves from a Monte Carlo simulation. These curves indicate a substantial increase in detection rate when three males are evaluated per litter rather than one. A 10% effect across male pups would be detected 5% of the time if one pup per litter was evaluated, but these effects would be detected 66% of the time if three pups per litter were evaluated. Taken together, this study provides a well-defined dose response of DEHP-induced RTMs and demonstrates that retention of more adult F1 and F2 males per litter, animals that were already produced, increases the ability to detect RTMs and presumably other low-incidence phenomena.

Environmental and Molecular MutagenesisVolume 51, Issue 8-9 p. 744-745 In Memoriam Memorial for John Wassom† Suzanne Morris, Suzanne Morris National Center for Toxicology Research, US FDA, Jefferson, ArkansasSearch for more papers by this authorJack Bishop, Jack Bishop National Center for Toxicology Research, US FDA, Jefferson, ArkansasSearch for more papers by this authorBarbara Parsons, Barbara Parsons National Center for Toxicology Research, US FDA, Jefferson, ArkansasSearch for more papers by this author Suzanne Morris, Suzanne Morris National Center for Toxicology Research, US FDA, Jefferson, ArkansasSearch for more papers by this authorJack Bishop, Jack Bishop National Center for Toxicology Research, US FDA, Jefferson, ArkansasSearch for more papers by this authorBarbara Parsons, Barbara Parsons National Center for Toxicology Research, US FDA, Jefferson, ArkansasSearch for more papers by this author First published: 24 September 2010 https://doi.org/10.1002/em.20620 † This article is a US Government work and, as such, is in the public domain in the United States of America. Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL No abstract is available for this article. Volume51, Issue8-9October ‐ December 2010Pages 744-745 RelatedInformation

Consistent high-quality of papers published in Mutation Research-Reviews in Mutation Research can only be maintained with the co-operation and dedication of a number of expert referees. The Editors would like to thank all those who have donated the hours necessary to review, evaluate and comment on manuscripts; their conscientious efforts have enabled the journal to maintain its tradition of excellence. We are grateful to the following reviewers for their contributions during 2007.

Chromosomal mosaicism in human preimplantation embryos is a common cause of spontaneous abortions, however, our knowledge of its etiology is limited. We used multicolor fluorescence in situ hybridization painting to investigate whether paternally transmitted chromosomal aberrations result in mosaicism in mouse two-cell embryos. Paternal exposure to acrylamide, an important industrial chemical also found in tobacco smoke and generated during the cooking process of starchy foods, produced significant increases in chromosomally defective two-cell embryos, however, the effects were transient primarily affecting the postmeiotic stages of spermatogenesis. Comparisons with our previous study of zygotes demonstrated similar frequencies of chromosomally abnormal zygotes and two-cell embryos suggesting that there was no apparent selection against numerical or structural chromosomal aberrations. However, the majority of affected two-cell embryos were mosaics showing different chromosomal abnormalities in the two blastomeric metaphases. Analyses of chromosomal aberrations in zygotes and two-cell embryos showed a tendency for loss of acentric fragments during the first mitotic division of embryogenesis, whereas both dicentrics and translocations apparently underwent proper segregation. These results suggest that embryonic development can proceed up to the end of the second cell cycle of development in the presence of abnormal paternal chromosomes and that even dicentrics can persist through cell division. The high incidence of chromosomally mosaic two-cell embryos suggests that the first mitotic division of embryogenesis is prone to missegregation errors and that paternally transmitted chromosomal abnormalities increase the risk of missegregation leading to embryonic mosaicism.

Zidovudine-based antiretroviral therapies (ARTs) for treatment of HIV-infected pregnant women have markedly reduced mother-to-child transmission of the human immunodeficiency virus (HIV-1) from ∼25% to <1%. However, zidovudine (ZDV; AZT), a nucleoside analogue, induces chromosomal damage, gene mutations, and cancer in animals following direct or transplacental exposure. To determine if chromosomal damage is induced by ZDV in infants exposed transplacentally, we evaluated micronucleated reticulocyte frequencies (%MN-RET) in 16 HIV-infected ART-treated mother–infant pairs. Thirteen women received prenatal ART containing ZDV; three received ART without ZDV. All infants received ZDV for 6 weeks postpartum. Venous blood was obtained from women at delivery and from infants at 1–3 days, 4–6 weeks, and 4–6 months of life; cord blood was collected immediately after delivery. Ten cord blood samples (controls) were obtained from infants of HIV-uninfected women who did not receive ART. %MN-RET was measured using a single laser 3-color flow cytometric system. Tenfold increases in %MN-RET were seen in women and infants who received ZDV-containing ART prenatally; no increases were detected in three women and infants who received prenatal ART without ZDV. Specifically, mean %MN-RET in cord blood of ZDV-exposed infants was 1.67 ± 0.34 compared with 0.16 ± 0.06 in non-ZDV ART-exposed infants ( P = 0.006) and 0.12 ± 0.02 in control cord bloods ( P < 0.0001). %MN-RET in ZDV-exposed newborns decreased over the first 6 months of life to levels comparable to cord blood controls. These results demonstrate that transplacentalZDV exposure is genotoxic in humans. Long-term monitoring of HIV-uninfected ZDV-exposed infants isrecommended to ensure their continued health. Environ. Mol. Mutagen. Published 2007 Wiley-Liss, Inc.

Birth defects, de novo genetic diseases, and chromosomal abnormality syndromes occur in ∼5% of all live births, and affected children suffer from a broad range of lifelong health consequences. Despite the social and medical impact of these defects, and the 8 decades of research in animal systems that have identified numerous germ-cell mutagens, no human germ-cell mutagen has been confirmed to date. There is now a growing consensus that the inability to detect human germ-cell mutagens is due to technological limitations in the detection of random mutations rather than biological differences between animal and human susceptibility. A multidisciplinary workshop responding to this challenge convened at The Jackson Laboratory in Bar Harbor, Maine. The purpose of the workshop was to assess the applicability of an emerging repertoire of genomic technologies to studies of human germ-cell mutagenesis. Workshop participants recommended large-scale human germ-cell mutation studies be conducted using samples from donors with high-dose exposures, such as cancer survivors. Within this high-risk cohort, parents and children could be evaluated for heritable changes in (a) DNA sequence and chromosomal structure, (b) repeat sequences and minisatellites, and (c) global gene expression profiles and pathways. Participants also advocated the establishment of a bio-bank of human tissue samples from donors with well-characterized exposure, including medical and reproductive histories. This mutational resource could support large-scale, multiple-endpoint studies. Additional studies could involve the examination of transgenerational effects associated with changes in imprinting and methylation patterns, nucleotide repeats, and mitochondrial DNA mutations. The further development of animal models and the integration of these with human studies are necessary to provide molecular insights into the mechanisms of germ-cell mutations and to identify prevention strategies. Furthermore, scientific specialty groups should be convened to review and prioritize the evidence for germ-cell mutagenicity from common environmental, occupational, medical, and lifestyle exposures. Workshop attendees agreed on the need for a full-scale assault to address key fundamental questions in human germ-cell environmental mutagenesis. These include, but are not limited to, the following: Do human germ-cell mutagens exist? What are the risks to future generations? Are some parents at higher risk than others for acquiring and transmitting germ-cell mutations? Obtaining answers to these, and other critical questions, will require strong support from relevant funding agencies, in addition to the engagement of scientists outside the fields of genomics and germ-cell mutagenesis. Environ. Mol. Mutagen., 2007. Published 2007 Wiley-Liss, Inc.

Although numerous germ-cell mutagens have been identified inanimal model systems, to date, no human germ-cell mutagens have beenconfirmed. Because the genomic integrity of our germ cells is essentialfor the continuation of the human species, a resolution of this enduringconundrum is needed. To facilitate such a resolution, we organized aworkshop at The Jackson Laboratory in Bar Harbor, Maine on September28-30, 2004. This interactive workshop brought together scientists from awide range of disciplines to assess the applicability of emergingmolecular methods for genomic analysis to the field of human germ-cellmutagenesis. Participants recommended that focused, coordinated humangerm-cell mutation studies be conducted in relation to important societalexposures. Because cancer survivors represent a unique cohort withwell-defined exposures, there was a consensus that studies should bedesigned to assess the mutational impact on children born to parents whohad received certain types of mutagenic cancer chemotherapy prior toconceiving their children. Within this high-risk cohort, parents andchildren could be evaluated for inherited changes in (a) gene sequencesand chromosomal structure, (b) repeat sequences and minisatelliteregions, and (c) global gene expression and chromatin. Participants alsorecommended studies to examine trans-generational effects in humansinvolving mechanisms such as changes in imprinting and methylationpatterns, expansion of nucleotide repeats, or induction of mitochondrialDNA mutations. Workshop participants advocated establishment of abio-bank of human tissue samples that could be used to conduct amultiple-endpoint, comprehensive, and collaborative effort to detectexposure-induced heritable alterations in the human genome. Appropriateanimal models of human germ-cell mutagenes is should be used in parallelwith human studies to provide insights into the mechanisms of mammaliangerm-cell mutagenesis. Finally, participants recommended that scientificspecialty groups be convened to address specific questions regarding thepotential germ-cell mutagenicity of environmental, occupational, andlifestyle exposures. Strong support from relevant funding agencies andengagement of scientists outside the fields of genomics and germ-cellmutagenesis will be required to launch a full-scale assault on some ofthe most pressing and enduring questions in environmental mutagenesis: Dohuman germ-cell mutagens exist, what risk do they pose to futuregenerations, and are some parents at higher risk than others foracquiring and transmitting germ-cell mutations?

Zidovudine‐based antiretroviral therapies (ARTs) for treatment of HIV‐infected pregnant women have markedly reduced mother‐to‐child transmission of the human immunodeficiency virus (HIV‐1) from ∼25% to <1%. However, zidovudine (ZDV; AZT), a nucleoside analogue, induces chromosomal damage, gene mutations, and cancer in animals following direct or transplacental exposure. To determine if chromosomal damage is induced by ZDV in infants exposed transplacentally, we evaluated micronucleated reticulocyte frequencies (%MN‐RET) in 16 HIV‐infected ART‐treated mother–infant pairs. Thirteen women received prenatal ART containing ZDV; three received ART without ZDV. All infants received ZDV for 6 weeks postpartum. Venous blood was obtained from women at delivery and from infants at 1–3 days, 4–6 weeks, and 4–6 months of life; cord blood was collected immediately after delivery. Ten cord blood samples (controls) were obtained from infants of HIV‐uninfected women who did not receive ART. %MN‐RET was measured using a single laser 3‐color flow cytometric system. Tenfold increases in %MN‐RET were seen in women and infants who received ZDV‐containing ART prenatally; no increases were detected in three women and infants who received prenatal ART without ZDV. Specifically, mean %MN‐RET in cord blood of ZDV‐exposed infants was 1.67 ± 0.34 compared with 0.16 ± 0.06 in non‐ZDV ART‐exposed infants (P = 0.006) and 0.12 ± 0.02 in control cord bloods (P < 0.0001). %MN‐RET in ZDV‐exposed newborns decreased over the first 6 months of life to levels comparable to cord blood controls. These results demonstrate that transplacentalZDV exposure is genotoxic in humans. Long‐term monitoring of HIV‐uninfected ZDV‐exposed infants isrecommended to ensure their continued health. Environ. Mol. Mutagen. Published 2007 Wiley‐Liss, Inc.