In early ''

Drosophila ''Drosophila'' () is a genus of flies, belonging to the family Drosophilidae, whose members are often called "small fruit flies" or (less frequently) pomace flies, vinegar flies, or wine flies, a reference to the characteristic of many species ...

development Development or developing may refer to: Arts *Development hell, when a project is stuck in development *Filmmaking, development phase, including finance and budgeting *Development (music), the process thematic material is reshaped * Photograph ...

, the first 13 cells pass through

mitosis In cell biology, mitosis () is a part of the cell cycle in which replicated chromosomes are separated into two new nuclei. Cell division by mitosis gives rise to genetically identical cells in which the total number of chromosomes is mainta ...

are nuclear divisions (karyokinesis) without

cytokinesis Cytokinesis () is the part of the cell division process 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 in mitosis and meios ...

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

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

, but strictly a

coenocyte A coenocyte () is a multinucleate cell which can result from multiple nuclear divisions without their accompanying cytokinesis, in contrast to a syncytium, which results from cellular aggregation followed by dissolution of the cell membranes insid ...

). Pole cells are the cells that form at the polar ends of the Drosophila egg, which begin the adult germ cells. Pole plasm functions to bud the development of pole cells, as well as restore

fertilization Fertilisation or fertilization (see spelling differences), also known as generative fertilisation, syngamy and impregnation, is the fusion of gametes to give rise to a new individual organism or offspring and initiate its development. Proce ...

, even when the cell was previously sterile.

Formation

During early development of the ''Drosophila'' development, pole plasm assembles at the

posterior pole In ophthalmology, the posterior pole is the back of the eye, usually referring to the retina between the optic disc and the macula.Cassin, B. and Solomon, S. ''Dictionary of Eye Terminology''. Gainesville, Florida: Triad Publishing Company, 1990. ...

of the ''Drosophila'' embryo, allowing determination of the abdominal patterning. Late in

oogenesis Oogenesis, ovogenesis, or oögenesis 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 in the embryonic stage. O ...

polar organelle A polar organelle is a structure at a specialised 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 ultrathi ...

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. ...

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 Oskar may refer to: * oskar (gene), the Drosophila gene * Oskar (given name) Oscar or Oskar is a masculine given name of Irish origin. Etymology The name is derived from two elements in Irish: the first, ''os'', means "deer"; the second element, ' ...

, 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