Diverse and variable sex determination mechanisms in vertebrates.

Sex is prevalent in nature and sex determination is one of the most fundamental biological processes, while the way of initiating female and male development exhibits remarkable diversity and variability across vertebrates. The knowledge on why and how sex determination mechanisms evolve unusual plasticity remains limited. Here, we summarize sex determination systems, master sex-determining genes and gene-regulatory networks among vertebrates. Recent research advancements on sex determination system transition are also introduced and discussed in some non-model animals with multiple sex determination mechanisms. This review will provide insights into the origin, transition and evolutionary adaption of different sex determination strategies in vertebrates, as well as clues for future perspectives in this field.