Drosophila Argonaute 1 and its miRNA biogenesis partners are required for oocyte formation and germline cell division

Abstract

Argonaute 1 (Ago1) is a member of the Argonaute/PIWI protein family involved in small RNA-mediated gene regulation. In Drosophila, Ago1 plays a specific role in microRNA (miRNA) biogenesis and function. Previous studies have demonstrated that Ago1 regulates the fate of germline stem cells. However, the function of Ago1 in other aspects of oogenesis is still elusive. Here we report the function of Ago1 in developing egg chambers. We find that Ago1 protein is enriched in the oocytes and also highly expressed in the cytoplasm of follicle cells. Clonal analysis of multiple ago1 mutant alleles shows that many mutant egg chambers contain only 8 nurse cells without an oocyte which is phenocopied in dicer-1, pasha and drosha mutants. Our results suggest that Ago1 and its miRNA biogenesis partners play a role in oocyte determination and germline cell division in Drosophila.

Responses of the Housefly, Musca domestica, to the Hytrosavirus Replication: Impacts on Host's Vitellogenesis and Immunity

“…Argonaute-2 (Ago-2) executes siRNA-mediated gene silencing (Okamura et al, 2004). Interestingly, Ago1 was downregulated by MdSGHV infection; Ago-1 is important in production of miRNAs that are crucial to oogenesis (Nakahara et al, 2005; Azzam et al, 2012). Disruption of LmAgo-1 by RNAi dramatically decreased vitellogenin transcription and severely impaired follicular epithelium development, terminal oocyte maturation, and ovarian growth, supporting the notion that Ago1-dependent miRNAs are required for JH-mediated vitellogenesis and egg production in locusts (Song et al, 2013).…”

Drosha-independent DGCR8/Pasha pathway regulates neuronal morphogenesis

“…These data indicated a role for Pasha in ɣ neuron morphogenesis that was not shared with other miRNA pathway members. The reported similarity between drosha and pasha null phenotypes in the female germ line (30) further suggested that this miRNA-independent function of Pasha might be specific to neurons.…”

“…Phenotypic differences have been previously described among pasha, dcr-1, and ago1 mutant GH146-Gal4-labeled adPN clones: defects in adPN targeting and dendritic density were highly penetrant in clones of the lethal, protein-null pasha LL03660 allele, moderately penetrant in clones of the lethal, transcript-null dcr-1 LL06357 allele, and absent in clones of the hypomorphic ago1 K08121 allele (18). These phenotypes were interpreted as evidence for miRNA function in neurons, because the differences could have been due to the relative strengths of the alleles used: none were molecular nulls, and neither pasha LL03660 nor ago1 K08121 acted like genetic nulls in subsequent analyses (24,30). This interpretation of neuronal miRNA function would be supported if drosha null alleles displayed adPN morphogenesis defects similar to pasha, dcr-1, and ago1 null alleles.…”

Adult-specific functions of animal microRNAs

“…Mutant clones of the bantam miRNA exhibit progressive GSC loss, indicating its relevance to GSC dynamics 26 . More recently, analysis of drosha , pasha , dicer-1 and ago1 mutant clones revealed a common requirement for the miRNA pathway in oocyte determination and germline cell division 27 .…”