The role of PIWI and the miRNA machinery in Drosophila germline determination

Curr Biol. 2006 Oct 10;16(19):1884-94. doi: 10.1016/j.cub.2006.08.051. Epub 2006 Aug 31.

Abstract

Background: The germ plasm has long been demonstrated to be necessary and sufficient for germline determination, with translational regulation playing a key role in the process. Beyond this, little is known about molecular activities underlying germline determination.

Results: We report the function of Drosophila PIWI, DICER-1, and dFMRP (Fragile X Mental Retardation Protein) in germline determination. PIWI is a maternal component of the polar granule, a germ-plasm-specific organelle essential for germline specification. Depleting maternal PIWI does not affect OSK or VASA expression or abdominal patterning but leads to failure in pole-plasm maintenance and primordial-germ-cell (PGC) formation, whereas doubling and tripling the maternal piwi dose increases OSK and VASA levels correspondingly and doubles and triples the number of PGCs, respectively. Moreover, PIWI forms a complex with dFMRP and DICER-1, but not with DICER-2, in polar-granule-enriched fractions. Depleting DICER-1, but not DICER-2, also leads to a severe pole-plasm defect and a reduced PGC number. These effects are also seen, albeit to a lesser extent, for dFMRP, another component of the miRISC complex.

Conclusions: Because DICER-1 is required for the miRNA pathway and DICER-2 is required for the siRNA pathway yet neither is required for the rasiRNA pathway, our data implicate a crucial role of the PIWI-mediated miRNA pathway in regulating the levels of OSK, VASA, and possibly other genes involved in germline determination in Drosophila.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Animals
  • Argonaute Proteins
  • Body Patterning / physiology
  • Cell Differentiation
  • DEAD-box RNA Helicases / genetics
  • DEAD-box RNA Helicases / metabolism
  • Drosophila / embryology*
  • Drosophila / genetics
  • Drosophila / metabolism
  • Drosophila Proteins / genetics
  • Drosophila Proteins / metabolism
  • Drosophila Proteins / physiology
  • Embryo, Nonmammalian / cytology
  • Embryo, Nonmammalian / metabolism
  • Embryonic Development / physiology
  • Fragile X Mental Retardation Protein / genetics
  • Fragile X Mental Retardation Protein / metabolism
  • Fragile X Mental Retardation Protein / physiology
  • Gene Expression Regulation, Developmental
  • Germ Cells / cytology
  • Germ Cells / metabolism*
  • MicroRNAs / physiology*
  • Proteins / physiology*
  • RNA Helicases / genetics
  • RNA Helicases / metabolism
  • RNA Helicases / physiology
  • RNA, Small Interfering / metabolism
  • RNA-Induced Silencing Complex
  • Ribonuclease III

Substances

  • Argonaute Proteins
  • Drosophila Proteins
  • MicroRNAs
  • Proteins
  • RNA, Small Interfering
  • RNA-Induced Silencing Complex
  • osk protein, Drosophila
  • piwi protein, Drosophila
  • Fragile X Mental Retardation Protein
  • DCR-2 protein, Drosophila
  • Dcr-1 protein, Drosophila
  • Ribonuclease III
  • vas protein, Drosophila
  • DEAD-box RNA Helicases
  • RNA Helicases