Research Themes

Unveiling the secret of germline cells: the heir of the lives beyond birth and death of individuals

Thought higher animals do die as individuals, their species are maintained by sexual reproduction. Individuals are just like vehicles in which passenger –genetic information– can ride to be inherited to next generation by germline lineage. As such, germline cells are the most important cells to maintain the species. Drosophila melanogaster is one of the ideal model organisms we can study gametogenesis. How are germline stem cells maintained in the microenvironment, niche? What is the molecular mechanism that controls germline cells to mature into egg and sperm? How genome in germline cells safely guarded by non-coding RNA from transposons attacks? Our group has been addressing such molecular mechanisms for better understanding of gametogenesis.

A confocal image showing one of Tudor domain proteins, Tejas (fly TDRD5 homolog), localized to nuage (red). Piwi involved in nuclear processing of piRNAs is shown in green. Tejas appears foci on the cytoplasmic face of the nurse cell nuclei.

A confocal image showing one of Tudor domain proteins, Tejas (fly TDRD5 homolog), localized to nuage (red). Piwi involved in nuclear processing of piRNAs is shown in green. Tejas appears foci on the cytoplasmic face of the nurse cell nuclei.

Nuage dynamics with live-imaging

Published Articles

Research articles

  • Teo RYW, Anand A, Sridhar V, Okamura K, Kai T. (2018) Heterochromatin protein 1a functions for piRNA biogenesis predominantly from pericentric and telomeric regions in Drosophila. Nat. Commun. 9:1735
  • Quénerch’du E, Anand A, Kai T. (2016) The piRNA pathway is developmentally regulated during spermatogenesis in Drosophila. RNA 22(7):1044–1054
  • Patil VS, Anand A, Chakrabarti, A, Kai T. (2014) The Tudor domain protein Tapas, a homolog of the vertebrate Tdrd7, functions in piRNA pathway to regulate retrotransposons in germline of Drosophila melanogaster. BMC Biol. 12:61
  • Anand A, Kai T. (2014) Response to ‘Antisense piRNA amplification, but not piRNA production or nuage assembly, requires the Tudor-domain protein Qin’ (Correspondence). EMBO J. 33(6):540–541
  • Lim RSM, Anand A, Nishimiya-Fujisawa C, Kobayashi S, Kai T. (2014) Analysis of Hydra PIWI proteins and piRNAs uncover early evolutionary origins of the piRNA pathway. Dev. Biol. 386(1):237–251
  • Pek JW, Ng BF, Kai T. (2012) Polo-mediated phosphorylation of Maelstrom regulates oocyte determination. Development 139(24):4505–4513
  • Anand A, Kai T. (2012) The tudor domain protein Kumo is required to assemble the nuage and to generate germline piRNAs in Drosophila. EMBO J. 31(4):870–882
  • Pek JW, Kai T. (2011) DEAD-box RNA helicase Belle/DDX3 and the RNA interference pathway promote mitotic chromosome segregation. Proc. Natl. Acad. Sci. USA 108(29):12007–12012
  • Pek JW, Kai T. (2011) A role for Vasa in regulating mitotic chromosome condensation in Drosophila. Curr. Biol. 21(1):39–44
  • Patil VS, Kai T. (2010) Repression of retroelements in Drosophila germline via piRNA pathway by the tudor domain protein Tejas. Curr. Biol. 20(8):724–730
  • Pek JW, Lim AK, Kai T. (2009) Drosophila Maelstrom Ensures Proper Germline Stem Cell Lineage Differentiation by Repressing microRNA-7. Dev. Cell 17(3):417–424
  • Lim AK, Tao L, Kai T. (2009) piRNAs mediate post-transcriptional retroelement silencing and localization to pi-bodies in the Drosophila germline. J. Cell Biol. 186(3):333–342
  • Lim AK, Kai T. (2007) Unique germ-line organelle, nuage, functions to repress selfish genetic elements in Drosophila melanogaster. Proc. Natl. Acad. Sci. USA 104(16):6714–6719
  • Kai T, Williams D, Spradling AC. (2005) The expression profile of purified Drosophila germline stem cells. Dev. Biol. 283(2):486–502
  • Kai T, Spradling A. (2004) Differentiating germ cells can revert into functional stem cells in Drosophila melanogaster ovaries. Nature 428(6982):564–569
  • Kai T, Spradling A. (2003) An empty Drosophila stem cell niche reactivates the proliferation of ectopic cells. Proc. Natl. Acad. Sci. USA 100(8):4633–4638

Review articles

  • Niwa R, Kai T. (2020) Editorial overview: Stem cells orchestrate oogenesis: a lesson from the fruit fly, Drosophila melanogaster. Curr. Opin. Insect Sci 37:iii–v
  • Gleason RJ, Anand A, *Kai T, *Chen X. (2017) Protecting and diversifying the germline. ** 208(2):435–471 (A part of FLY BOOK) *Co-corresponding
  • Lim RSM, Kai T. (2015) A piece of the pi(e): the diverse roles of animal piRNAs and their PIWI partners. Sem. Cell Dev. Biol. 47–48:17–31 (Special Issue on Coding and Non-coding RNAs)
  • Pek JW, Anand A, Kai T. (2012) Tudor domain proteins in development (Invited Review Article). Development 139:2255–2266
  • Pek JW, Patil VS, Kai T. (2012) The piRNA pathway and the potential processing site, the nuage, in the Drosophila germline. Dev. Growth Differ. 54(1):66–77
  • Pek JW, Kai T. (2011) Non-coding RNAs enter mitosis: functions, conservation and implications. Cell Div. 6:6
  • Pek JW, Kai T. (2009) Conserved germline organelle, nuage, serves as site for processing of Piwi-interacting RNAs. (in Japanese). Exp. Med. 27:393–399
  • Kai T. (2004) Germline stem cells and their niches. (in Japanese). Tanpakushitsu Kakusan Koso 49(6):710–717
  • Spradling A, Drummond-Barbosa D, Kai T. (2001) Stem cells find their niche. Nature 414(6859):98–104

Protocol articles

  • Lim RS, Osato M, Kai T. (2015) Isolation of undifferentiated female germline cells from adult Drosophila ovaries. Curr. Protoc. Stem Cell Biol. 34:2E.3.1–2E.3.15