The follicle stem cell lineage in telotrophic Tribolium oogenesis
Zusammenfassung der Projektergebnisse
The beetle Tribolium represents telotrophic ovaries, which differ fundamentally from the polytrophic ovary of Drosophila. In Tribolium, the formation and maintenance of the adult follicle stem cell (FSC) linage is largely independent of the germline stem cells (GSCs), as germline proliferation is restricted to larval and early pupal stages. The follicle stem cell niche, however, remains active up to adulthood. Thus, the somatic stem cell lineage can be studied using systemic RNAi without affecting the formation of germ cells, which makes Tribolium an attractive model system to identify and study the genetic regulation of FSCs. Of the 3116 genes screened in the second phase, 574 (18,4%) resulted in the cessation of eggproduction. Of those, 226 (39,4%) either did not show any obvious phenotypes, or turned out to be "held-egg" phenotypes. For 157 (27,3%) genes, we observed “starvation phenotypes”, which manifests in degeneration of the fat body and ovaries. 28 (4,9%) candidates showed rather global defects, in which germline derived cells (e.g. nurse cells and oocytes) as well as the somatic follicle cell lineages were affected, indicating rather general (maybe housekeeping) function in cell maintenance or survival. The remaining 163 genes (28,4% the 574 "no-egg" phenotypes) were scored for the loss or reduction of developing follicles and somatic tissue. Among others we identified Tc003132 as a prime candidate for differentiation and / or maintenance of FSC linage. Tc003132 belongs to the Casein Kinase 2 substrate (CK2S) family (accession: pfam15011), which in humans is associated with the proliferative activity of different cancers. Upon Tc03132 RNAi, central pre-follicular cells are lost, which results in termination of oogenesis. Given that also Notch-signalling is required to promote the mitotic activity of central pre-follicular cells, we performed epistasis experiments with Notch and cut. We found that Tc003132 depleted pre-follicular cells neither reacts to mitosis or endocycle stimulating signals. Hence, Tc003132 may be required to provide competence for differentiation cues, which may resemble the situation in C. elegans were CK2 is required to maintain the balance between proliferation and differentiation in the germ line. By monitoring the mitotic pattern of wild-type and Tc003132 depleted follicle cells by EDU incorporations, we identified a putative follicle stem cell population. In Tc003132 RNAi these putative FSC cease the expression of differentiation makers and eventfully are lost. These results suggest that Tc003132 might be required for the proliferation or maintenance of follicle stem cells in the telotrophic Tribolium ovary.
Projektbezogene Publikationen (Auswahl)
- 2015. iBeetle-Base: a database for RNAi phenotypes in the red flour beetle Tribolium castaneum. Nucleic Acids Res. 43, D720–D725
Dönitz, J., Schmitt-Engel, C., Grossmann, D., Gerischer, L., Tech, M., Schoppmeier, M., Klingler, M., Bucher, G.
(Siehe online unter https://doi.org/10.1093/nar/gku1054) - 2015. Large scale RNAi screen in Tribolium reveals novel target genes for pest control and the proteasome as prime target. BMC Genomics 16
Ulrich, J., Dao, V.A., Majumdar, U., Schmitt-Engel, C., Schwirz, J., Schultheis, D., Ströhlein, N., Trelenberg, N., Grossmann, D., Richter, T., Dönitz, J., Gerischer, L., Leboulle, G., Vilcinskas, A., Stanke, M., Bucher, G.
(Siehe online unter https://doi.org/10.1186/s12864-015-1880-y) - 2015. The iBeetle large-scale RNAi screen reveals gene functions for insect development and physiology. Nat. Commun. 6, 7822
Schmitt-Engel, C., Schultheis, D., Schwirz, J., Ströhlein, N., Troelenberg, N., Majumdar, U., Dao, V.A., Grossmann, D., Richter, T., Tech, M., Dönitz, J., Gerischer, L., Theis, M., Schild, I., Trauner, J., Koniszewski, N.D.B., Küster, E., Kittelmann, S., Hu, Y., Lehmann, S., Siemanowski, J., Ulrich, J., Panfilio, K.A., Schröder, R., Morgenstern, B., Stanke, M., Buchhholz, F., Frasch, M., Roth, S., Wimmer, E.A., Schoppmeier, M., Klingler, M., Bucher, G.
(Siehe online unter https://doi.org/10.1038/ncomms8822)
