In early ''Drosophila'' development, the embryo passes through thirteen nuclear divisions (karyokinesis) without

cytokinesis Cytokinesis () is the part of the cell division process and part of mitosis during which the cytoplasm of a single eukaryotic cell divides into two daughter cells. Cytoplasmic division begins during or after the late stages of nuclear division ...

, resulting in a multinucleate cell (generally referred to as a

syncytium A syncytium (; : syncytia; from Greek: σύν ''syn'' "together" and κύτος ''kytos'' "box, i.e. cell") or symplasm is a multinucleate cell that can result from multiple cell fusions of uninuclear cells (i.e., cells with a single nucleus), i ...

, but strictly a coenocyte). Pole cells are the cells that form at the polar ends of the ''

Drosophila ''Drosophila'' (), from Ancient Greek δρόσος (''drósos''), meaning "dew", and φίλος (''phílos''), meaning "loving", is a genus of fly, belonging to the family Drosophilidae, whose members are often called "small fruit flies" or p ...

'' egg, which begin the adult germ cells. Pole plasm functions to bud the pole cells, as well as restore

fertilization Fertilisation or fertilization (see American and British English spelling differences#-ise, -ize (-isation, -ization), spelling differences), also known as generative fertilisation, syngamy and impregnation, is the fusion of gametes to give ...

, even when the cell was previously sterile.

Formation

During early

development Development or developing may refer to: Arts *Development (music), the process by which thematic material is reshaped * Photographic development *Filmmaking, development phase, including finance and budgeting * Development hell, when a proje ...

of ''Drosophila'', pole plasm assembles at the posterior pole of the ''Drosophila'' embryo, allowing determination of the abdominal patterning. Late in

oogenesis Oogenesis () or ovogenesis is the differentiation of the ovum (egg cell) into a cell competent to further develop when fertilized. It is developed from the primary oocyte by maturation. Oogenesis is initiated before birth during embryonic devel ...

polar organelle A polar organelle is a structure at a specialized region of the bacterial polar membrane that is associated with the flagellar apparatus. This flagellum-associated structure can easily be distinguished from the other membrane regions in ult ...

s, which are electro-negative granules, are in the pole plasm. When the pole plasm further matures, it continues to consist of polar granules into the development of germ cells, which develop into adult germ cells.

Serine protease Serine proteases (or serine endopeptidases) are enzymes that cleave peptide bonds in proteins. Serine serves as the nucleophilic amino acid at the (enzyme's) active site. They are found ubiquitously in both eukaryotes and prokaryotes. Serin ...

activity occurs less than 2 hours after the budding of the pole cells from the pole plasm, and ending just prior to the movement of the pole cells via gastrulation. The patterning of the pole cells are determined by the activation of oskar, which acts in the determination of body patterning segments. Pole cells begin their migration in a cluster in the midgut primordium. To reach their final destination, pole cells must migrate through the epithelial wall. It is known that the cells migrate through the epithelial wall, but little is known about the mechanisms used to do so.

References

Mitosis {{cell-cycle-stub