Primordial Germ Cell Development in Teleosts: Their Origin, Fate and Role in Sex Determination.

In the context of sexual reproduction, primordial germ cells (PGCs) are the progenitors of life; they develop into gametes and safeguard fertility. By virtue of their diverse reproductive strategies, fishes provide appealing models to study germ cell formation and functional gonadogenesis. This review aims to consolidate our understanding of PGC development in teleosts by evaluating the developmental milestones of germ cell formation in contrast with other model animals. Here, we revisit germ plasm assembly in gametes, re-examining the extent and nature of parental contributions to germ cell inheritance. We further examine how germ cell fate in teleosts is governed by germ plasm inheritance, whereby lineage identity arises through selective retention and stabilisation of maternal determinants rather than de novo specification. Following this, we demonstrate that a coordinated network of molecular pathways and effector genes drives PGC signalling, mobilization, and homing to the gonadal niche. Then, we highlight that, in contrast to mammals, teleost germ cell specification is largely uncoupled from genome-wide epigenetic reprogramming and instead relies on maternally inherited messages and post-transcriptional regulation to establish germline identity. Finally, we explore the interplay between newly harboured germ cells and gonadal somatic cells that underpins sexual identity acquisition. Collectively, these findings establish a conceptual framework in which germ plasm inheritance, post-transcriptional regulation, and soma-germline interactions jointly govern germ cell fate, sexual identity, and functional fertility in teleosts.