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Background: Anti-HER2 monoclonal antibody is associated with a greater risk of heart failure (HF) in female breast cancer patients. In recent years, the indication of anti-HER2 monoclonal antibodies was further expanded to stomach, colorectal, and salivary gland cancers regardless of sex in Japan. However, there have been no data on sex difference in the risk of HF after the anti-HER2 monoclonal antibody treatment., Objectives: We compared the risk of HF between male and female cancer patients treated with anti-HER2 monoclonal antibody using a nationwide population-based database., Method: We analyzed 4,608 cancer patients (230 men, median age; 52 years, breast cancer; 4,333) treated with HER2 monoclonal antibody enrolled in the JMDC Claims Database. The primary outcome was the incidence of HF., Results: Over a mean follow-up of 917 ± 835 days, 559 HF events were documented. Kaplan-Meier curves showed no significant difference in the incidence of HF between men and women. Multivariable Cox regression analysis showed that male sex was not associated with a risk of HF compared with women (HR, 0.76; 95% CI: 0.39-1.49)., Conclusions: Our analysis of a nationwide population-based database firstly revealed that no significant sex difference existed in the risk of HF among cancer patients treated with anti-HER2 monoclonal antibody. Our findings suggest that the use of anti-HER2 monoclonal antibodies in male patients may be associated with similar risks observed in female patients., (© 2023 The Author(s). Published by S. Karger AG, Basel.)

The availability of genome sequences from large numbers of species offers the prospect of studying genotype-phenotype correlations across various phylogenetic scales using only available data. A new study illustrates the power of this approach, showing an association across primates between morphological sexual dimorphism and the prevalence of a class of DNA elements that stimulate gene expression in response to male androgens., (© 2022 The Authors. Evolution © 2022 The Society for the Study of Evolution.)

DNA methylation is an ancient epigenetic pathway found across eukaryotes. Nevertheless, the targets of DNA methylation within genomes evolve extremely rapidly. Arthropods display many such examples. The mealybug Planococcus citri has evolved methylation at promoter sequences, associated with gene silencing just as in mammals. In this issue of Molecular Ecology, Bain et al. (2021), thoroughly characterise mealybug methylation, exploring its potential functions in gene expression and the spectacular sexual dimorphism that is a characteristic of this species. Their results provide new insights into the complex relationship between DNA methylation and gene expression and highlight how rapidly different methylation systems can evolve., (© 2021 The Authors. Molecular Ecology published by John Wiley & Sons Ltd.)

Sexual dimorphism can cause sexual antagonism of phenotypic traits. Lund-Hansen and colleagues (2020) investigated female-limited X chromosome evolution in Drosophila melanogaster using forced matrilineal inheritance. Body size and developmental time evolved toward their female optima, but reproductive fitness and locomotion remained unchanged. These findings imply that some sexually antagonized loci may be distributed across the genome and that some phenotypes may have already reached their female optima in nature., (© 2020 The Authors. Evolution © 2020 The Society for the Study of Evolution.)

Meiotic recombination affects fertility, shuffles genomes, and modulates the effectiveness of natural selection. Despite conservation of the recombination pathway, the rate of recombination varies among individuals and along chromosomes. Recombination rate also differs among cells from the same organism, but this form of variation has received less attention. To identify patterns that characterize intercellular variation in the genome-wide recombination rate, we counted foci of the MLH1 recombination-associated protein in oocytes and spermatocytes from a panel of wild-derived inbred strains of house mice. Females show higher intercellular variation in MLH1 focus count than males from the same inbred strains. This pattern is consistent across strains from multiple subspecies, including 2 strains in which the average MLH1 focus count is higher in males. The sex difference in genome-wide recombination rate we report suggests that selection targeting recombination rate will be more efficient in males than in females., (© 2021 S. Karger AG, Basel.)

Shortly after birth, mammals are colonized by a multitude of microbes derived from the mother and the environment. Studies in model organisms have demonstrated that the structure and composition of the gut microbiome of offspring steadily mature with increasing diversity during nursing and weaning (Sommer & Bäckhed, 2013). This period of microbiome assembly is critical for young mammals because the gut microbes they acquire will help train their immune system (Lathrop et al., 2011) with potential long-lasting effects on their health (Cox et al., 2014). In an article in this issue of Molecular Ecology, Stoffel et al. (2020) investigated the gut microbiota of northern elephant seals (Mirounga angustirostris) during a key developmental window. A month after giving birth, elephant seal mothers stop nursing their pups and return to the sea. As a consequence, their pups go from a diet of milk rich in fat to abruptly enter a post weaning fasting period which lasts for about two months while they remain with the colony. This particular life-history trait therefore offered the authors a unique and exciting opportunity to evaluate intrinsic factors contributing to gut microbiota development in a wild marine mammal., (© 2020 John Wiley & Sons Ltd.)

Cycloramphus and Zachaenus Neotropical frogs breed in rocky streams (saxicolous breeding) or in terrestrial environments. In their recent work, de Sá et al. investigate shifts between these habitats and the impact that these shifts have on body size and sexual size dimorphism (SSD). The researchers found that terrestrial breeding evolved on three occasions. Additionally, there was an association between habitat and SSD, with decreases in male body size correlating with shifts toward terrestrial breeding., (© 2019 The Authors. Evolution © 2019 The Society for the Study of Evolution.)

Why do some species exhibit apparently suboptimal combinations of life history traits? In a comparative study of lizard species, Reedy et al. test the idea that variation in the trade-off between fecundity and survival can be explained by sexual conflict. Their results show that degree of sexual conflict alone cannot explain this variation, and they found a positive correlation between trade-off optimality and the size of males relative to females. These findings suggest a more complicated picture of the fecundity-survival trade-off, possibly involving a third, unknown source of selective pressure., (© 2019 The Author(s). Evolution © 2019 The Society for the Study of Evolution.)

Selected twin research papers that are classic, provocative, and/or influential are surveyed. Many papers meet these criteria, so those chosen reflect the opinion of the author. Reviews of recent research on twin pregnancies with and without polycystic ovary syndrome, ectopic pregnancy, sex differences in cognition and maternal cardiac hemodynamics follow. Newsworthy twin-based items, including President Obama's portrait artist, the financial activities of the Winkelvoss twins, a set of triplet fashion models and the experience of seeing oneself in a painting, are summarized.

There is tremendous diversity in ageing rates and lifespan not only among taxa but within species, and particularly between the sexes. Women often live longer than men, and considerable research on this topic has revealed some of the potential biological, psychological and cultural causes of sex differences in human ageing and lifespan. However, sex differences in lifespan are widespread in nonhuman animals suggesting biology plays a prominent role in variation in ageing and lifespan. Recently, evolutionary biologists have borrowed techniques from biomedicine to identify whether similar mechanisms causing or contributing to variation in ageing and lifespan in humans and laboratory animals also operate in wild animals. Telomeres are repetitive noncoding DNA sequences capping the ends of chromosomes that are important for chromosomal stability but that can shorten during normal cell division and exposure to stress. Telomere shortening is hypothesized to directly contribute to the ageing process as once telomeres shorten to some length, the cells stop dividing and die. Men tend to have shorter telomeres and faster rates of telomere attrition with age than women, suggesting one possible biological cause of sex differences in lifespan. In this issue of Molecular Ecology, Watson et al. () show that telomere lengths in wild Soay sheep are similar between females and males near the beginning of life but quickly diverge with age because males but not females showed reduced telomere lengths at older ages. The authors further show that some of the observed sex difference in telomere lengths in old age may be due to male investment in horn growth earlier in life, suggesting that sexually dimorphic allocation to traits involved in sexual selection might underlie sex differences in telomere attrition. This study provides a rare example of how biological mechanisms potentially contributing to sex differences in lifespan in humans may also operate in free-living animals. However, future studies using a longitudinal approach are necessary to confirm these observations and identify the ultimate and proximate causes of any sex differences in telomere lengths. Collaborations between evolutionary biologists and gerontologists are especially needed to identify whether telomere lengths have a causal role in ageing, particularly in natural conditions, and whether this directly contributes to sex differences in lifespan., (© 2017 John Wiley & Sons Ltd.)

A comprehensive analysis of data from The Cancer Genome Atlas has shed light on molecular-level differences between men and women with cancer. The study researchers separated 13 cancers into "strong" and "weak" sex-effect groups; cancers in the former showed extensive sex-biased molecular signatures, including changes in a considerable number of clinically actionable genes., (©2016 American Association for Cancer Research.)