Pole cell explained

In early Drosophila development, the embryo passes through thirteen nuclear divisions (karyokinesis) without cytokinesis, resulting in a multinucleate cell (generally referred to as a syncytium, but strictly a coenocyte^[1]). Pole cells are the cells that form at the polar ends of the Drosophila egg, which begin the adult germ cells.^[2] Pole plasm functions to bud the pole cells, as well as restore fertilization, even when the cell was previously sterile.^[3]

Formation

During early development of Drosophila, pole plasm assembles at the posterior pole of the Drosophila embryo, allowing determination of the abdominal patterning. Late in oogenesis, polar organelles, 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.^[4] Serine protease 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.^[5] The patterning of the pole cells are determined by the activation of oskar, which acts in the determination of body patterning segments.^[6] 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.^[7]

Notes and References

1. Willmer, P. G. (1990). Invertebrate Relationships : Patterns in Animal Evolution. Cambridge University Press, Cambridge.
2. Saito. Kuniaki. 2013. The epigenetic regulation of transposable elements by PIWI-interacting RNAs in Drosophila. Genes & Genetic Systems. 88. 1. 9–17. 10.1266/ggs.88.9. 1341-7568. free.
3. Kobayashi. Satoru. Okada. Masukichi. August 1989. Mitochondrial lrRNA sequences restore pole cell-forming ability to UV-sterilized embryos. Cell Differentiation and Development. 27. 123. 10.1016/0922-3371(89)90382-1. 0922-3371.
4. Harria. Adam. Macdonald. Paul. 2001. aubergine encodes a Drosophila polar granule component required for pole cell formation and related to eIF2C. Development. 128. 2823–2832.
5. Jakobsen. Rasmus Kragh. Ono. Shin. Powers. James C.. DeLotto. Robert. 2004-12-18. Fluorescently labeled inhibitors detect localized serine protease activities in Drosophila melanogaster pole cells, embryos, and ovarian egg chambers. Histochemistry and Cell Biology. 123. 1. 51–60. 10.1007/s00418-004-0734-5. 15609041. 0948-6143.
6. Lin. Haifan. Wolfner. Mariana F.. Mariana Wolfner. January 1991. The Drosophila maternal-effect gene fs(1)Ya encodes a cell cycle-dependent nuclear envelope component required for embryonic mitosis. Cell. 64. 1. 49–62. 10.1016/0092-8674(91)90208-g. 0092-8674. free.
7. Callaini. Giuliano. Riparbelli. Maria Giovanna. Dallai. Romano. August 1995. Pole Cell Migration through the Gut Wall of the Drosophila Embryo: Analysis of Cell Interactions. Developmental Biology. 170. 2. 365–375. 10.1006/dbio.1995.1222. 7649369. 0012-1606. free.