Male meiosis at the helm: shaping genomes and sex chromosomes in emerging vertebrate models

The generation of haploid gametes is a hallmark of sexual reproduction achieved through a complex, albeit tightly regulated, reductional cell division known as meiosis. While the molecular underpinnings of meiosis have been extensively characterized in eutherian mammalian models, key aspects-particularly those governing chromosome synapsis and recombination-remain poorly understood in non-eutherian mammals and non-model vertebrates. This knowledge gap is especially relevant for understanding genome evolution, with a focus on sex chromosomes. Comparative studies across diverse vertebrate lineages are therefore essential to uncover conserved and lineage-specific features of meiotic regulation. In this review, we explore the evolutionary dynamics of meiosis in vertebrates, emphasizing how the meiotic program influences genome architecture and the evolution of heteromorphic sex chromosomes, especially the Y chromosome. As research in non-model species gains momentum, dissecting the diversity of meiotic mechanisms across taxa emerges as a key to understanding genome plasticity and evolutionary innovation.