Generation of primordial germ cell-like cells by two germ plasm components, dnd1 and nanos3, in medaka (Oryzias latipes)

In teleost fish, primordial germ cells (PGCs), the precursors of eggs and sperm, develop from cells that inherit maternal germ plasm (GP). Although numerous GP component genes have been identified, the minimum set of genes essential for germline formation remains unknown. Herein, we provide evidence that dnd1 and nanos3 synergistically induce PGC-like cells from the blastomeres of medaka embryos. One-cell stage embryos injected with dnd1 and nanos3 mRNA (DN-OE) showed developmental arrest before gastrulation and upregulation of PGC markers. Transplantation experiments revealed that most transplanted DN-OE blastomeres migrated into the gonadal ridge of host embryos, resulting in the production of functional eggs and sperm. Furthermore, the combination of genome editing and PGC induction techniques successfully generated transgenic knock-in medaka, demonstrating enhanced, precise, and stable gene integration. Identifying essential GP genes for PGC formation advances our understanding of germ cell development mechanisms and their biotechnological applications.