Migration of primordial germ cells and their relationship of PGCs with sex development in transgenic germline-specific fluorescent freshwater angelfish (Pterophyllum scalare)

Abstract

Primordial germ cells (PGCs), the progenitors of gametes, are essential for teleost reproduction. While their formation is conserved across teleosts, the activation, migration routes, and localization periods vary among species. In this study, we developed a novel transgenic line, Tg(ddx4:TcCFP13-nanos3), based on the Nile tilapia genome, to label PGCs with clear fluorescent signals in the freshwater angelfish (Pterophyllum scalare). Our findings reveal a complex, multistage PGCs migration process in angelfish, with a significantly extended localization period (168 hpf) compared to zebrafish (24 hpf). Notably, individual differences in PGCs abundance were observed during early somite development. Analysis of PGCs counts and subsequent sexual maturation demonstrate a potential correlation between PGCs abundance and sex determination: 90% of PGCs-reduced individuals developed as males, while 83% of PGCs-rich individuals developed as females. This study provides a foundation for understanding PGCs migration and sex development in freshwater angelfish, offering valuable insights into reproductive biology and ornamental fish species. Furthermore, this in vivo PGCs tracking system for Cichlids provides a versatile tool for advancing research and applications in germ cell biology.