title: The role of PIWI and the miRNA machinery in Drosophila germline determination.
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.
authors.affiliation: Department of Cell Biology and Duke University Medical Center, Durham, North Carolina 27705, USA.
authors.forename: Heather B
authors.initials: HB
authors.lastname: Megosh
authors.forename: Daniel N
authors.initials: DN
authors.lastname: Cox
authors.forename: Chris
authors.initials: C
authors.lastname: Campbell
authors.forename: Haifan
authors.initials: H
authors.lastname: Lin
mesh_terms: D000818:Animals; D060565:Argonaute Proteins; D019521:Body Patterning / Q000502:physiology; D002454:Cell Differentiation; D053487:DEAD-box RNA Helicases / Q000235:genetics / Q000378:metabolism; D004330:Drosophila / Q000196:embryology* / Q000235:genetics / Q000378:metabolism; D029721:Drosophila Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D004625:Embryo, Nonmammalian / Q000166:cytology / Q000378:metabolism; D047108:Embryonic Development / Q000502:physiology; D051860:Fragile X Messenger Ribonucleoprotein 1 / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D018507:Gene Expression Regulation, Developmental; D005854:Germ Cells / Q000166:cytology / Q000378:metabolism*; D035683:MicroRNAs / Q000502:physiology*; D011506:Proteins / Q000502:physiology*; D020365:RNA Helicases / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D034741:RNA, Small Interfering / Q000378:metabolism; D034743:RNA-Induced Silencing Complex; D043244:Ribonuclease III
chemical_list: D060565:Argonaute Proteins; D053487:DEAD-box RNA Helicases; D029721:Drosophila Proteins; D051860:Fragile X Messenger Ribonucleoprotein 1; D035683:MicroRNAs; D011506:Proteins; D020365:RNA Helicases; D034741:RNA, Small Interfering; D034743:RNA-Induced Silencing Complex; D043244:Ribonuclease III; C091675:osk protein, Drosophila; C116498:piwi protein, Drosophila; C478069:DCR-2 protein, Drosophila; C515033:Dcr-1 protein, Drosophila; C088269:vas protein, Drosophila