Polarcellen

Polarcellen, or pole cells, are germ cell precursors that are set aside during early embryonic development in certain animals, most notably insects such as Drosophila melanogaster. They originate from the germ plasm localized at the posterior pole of the egg and early embryo, which contains maternally supplied determinants that direct their fate.

Formation and determinants: The germ plasm carries specific RNA and protein factors, including genes such as oskar, nanos, and vasa, which establish the pole cells as the precursors of the future germ line. This maternal provisioning allows pole cells to be specified prior to widespread zygotic transcription and to remain separate from somatic lineages during early development.

Migration and role: Pole cells form at the posterior pole, invaginate, and then migrate through surrounding tissues to reach the developing gonads. There they proliferate and differentiate into primordial germ cells, which will later give rise to the sperm or eggs of the mature organism. Their migration is guided by signaling cues and cellular interactions that ensure proper colonization of the gonadal tissue.

Context and variation: Pole cells are a characteristic feature of certain invertebrates, especially many insects. In vertebrates, a related concept exists in the form of primordial germ cells, which originate from different embryonic regions and follow distinct migratory paths. The term polarcellen is commonly used in non-English or historical literature to denote this germ-line lineage.

See also: primordial germ cells, germ plasm, oskar, nanos, vasa.