Initiating mammalian reproduction from a single male genome

Sex in mammals is unidirectionally determined by the configuration of sex chromosomes. In contrast, several species, including fishes, can switch sexes in response to environmental cues, illustrating the reproductive advantages of sexual plasticity. Thus, technologies that can bypass the unidirectional nature of mammalian sex determination could open new avenues in reproductive biology. Here, by establishing a method that enables robust Y-chromosome elimination in embryos, we provide a strategy to regulate sex in mice. We show that this approach efficiently induces male-to-female sex reversal by releasing the Y chromosome as micronuclei during early development. When integrated with optimized somatic cell nuclear transfer, it enabled the parallel production of both male and sex-reversed female mice from a single male genome source. Offspring were successfully obtained from crosses between these male and sex-reversed female clones, demonstrating that this "dual-sex cloning" strategy can initiate sexual reproduction solely from a male somatic genome. These findings highlight dual-sex cloning as a valuable platform for securing mammalian reproduction and biodiversity from limited genetic resources.