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The let-7–Imp axis regulates ageing of the Drosophila testis stem-cell niche


Adult stem cells support tissue homeostasis and repair throughout the life of an individual. During ageing, numerous intrinsic and extrinsic changes occur that result in altered stem-cell behaviour and reduced tissue maintenance and regeneration. In the Drosophila testis, ageing results in a marked decrease in the self-renewal factor Unpaired (Upd), leading to a concomitant loss of germline stem cells. Here we demonstrate that IGF-II messenger RNA binding protein (Imp) counteracts endogenous small interfering RNAs to stabilize upd (also known as os) RNA. However, similar to upd, Imp expression decreases in the hub cells of older males, which is due to the targeting of Imp by the heterochronic microRNA let-7. In the absence of Imp, upd mRNA therefore becomes unprotected and susceptible to degradation. Understanding the mechanistic basis for ageing-related changes in stem-cell behaviour will lead to the development of strategies to treat age-onset diseases and facilitate stem-cell-based therapies in older individuals.

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Figure 1: Imp regulates upd levels and GSC maintenance in the testis.
Figure 2: Imp binds to upd mRNA and counteracts siRNA-mediated degradation.
Figure 3: Imp counteracts AGO2 and Dicer-2 to regulate upd levels and stem-cell maintenance.
Figure 4: Imp is targeted by let-7 miRNA in the testis.

Accession codes

Primary accessions

Gene Expression Omnibus

Data deposits

The small RNA libraries from the testes of 1-day-old and 30-day-old flies have been deposited in the Gene Expression Omnibus database under accession GSE37041.


  1. 1

    Schofield, R. The relationship between the spleen colony-forming cell and the haemopoietic stem cell. Blood Cells 4, 7–25 (1978)

    CAS  PubMed  Google Scholar 

  2. 2

    Jones, D. L. & Rando, T. A. Emerging models and paradigms for stem cell ageing. Nature Cell Biol. 13, 506–512 (2011)

    CAS  Article  Google Scholar 

  3. 3

    Voog, J. & Jones, D. L. Stem cells and the Niche: a dynamic duo. Cell Stem Cell 6, 103–115 (2010)

    CAS  Article  Google Scholar 

  4. 4

    Fuller, M. T. in The Development of Drosophila Melanogaster (eds Bate, M. & Martinez-Arias, A. ) 71–147 (Cold Spring Harbor Laboratory Press, 1993)

    Google Scholar 

  5. 5

    Boyle, M., Wong, C., Rocha, M. & Jones, D. L. Decline in self-renewal factors contributes to aging of the stem cell niche in the Drosophila testis. Cell Stem Cell 1, 470–478 (2007)

    CAS  Article  Google Scholar 

  6. 6

    Buszczak, M. et al. The carnegie protein trap library: a versatile tool for Drosophila developmental studies. Genetics 175, 1505–1531 (2007)

    CAS  Article  Google Scholar 

  7. 7

    Fabrizio, J. J. et al. Imp (IGF-II mRNA-binding protein) is expressed during spermatogenesis in Drosophila melanogaster . Fly 2, 47–48 (2008)

    Article  Google Scholar 

  8. 8

    Yisraeli, J. K. VICKZ proteins: a multi-talented family of regulatory RNA-binding proteins. Biol. Cell 97, 87–96 (2005)

    CAS  Article  Google Scholar 

  9. 9

    Brand, A. H., Manoukian, A. S. & Perrimon, N. Ectopic expression in Drosophila . Methods Cell Biol. 44, 635–654 (1994)

    CAS  Article  Google Scholar 

  10. 10

    Munro, T. P., Kwon, S., Schnapp, B. J. & St Johnston, D. A repeated IMP-binding motif controls oskar mRNA translation and anchoring independently of Drosophila melanogaster IMP. J. Cell Biol. 172, 577–588 (2006)

    CAS  Article  Google Scholar 

  11. 11

    Nabel-Rosen, H., Dorevitch, N., Reuveny, A. & Volk, T. The balance between two isoforms of the Drosophila RNA-binding protein how controls tendon cell differentiation. Mol. Cell 4, 573–584 (1999)

    CAS  Article  Google Scholar 

  12. 12

    Hafner, M. et al. Transcriptome-wide identification of RNA-binding protein and microRNA target sites by PAR-CLIP. Cell 141, 129–141 (2010)

    CAS  Article  Google Scholar 

  13. 13

    Bhattacharyya, S. N., Habermacher, R., Martine, U., Closs, E. I. & Filipowicz, W. Relief of microRNA-mediated translational repression in human cells subjected to stress. Cell 125, 1111–1124 (2006)

    CAS  Article  Google Scholar 

  14. 14

    Elcheva, I., Goswami, S., Noubissi, F. K. & Spiegelman, V. S. CRD-BP protects the coding region of βTrCP1 mRNA from miR-183-mediated degradation. Mol. Cell 35, 240–246 (2009)

    CAS  Article  Google Scholar 

  15. 15

    Czech, B. et al. An endogenous small interfering RNA pathway in Drosophila . Nature 453, 798–802 (2008)

    ADS  CAS  Article  Google Scholar 

  16. 16

    Lee, Y. S. et al. Distinct roles for Drosophila Dicer-1 and Dicer-2 in the siRNA/miRNA silencing pathways. Cell 117, 69–81 (2004)

    CAS  Article  Google Scholar 

  17. 17

    Carthew, R. W. & Sontheimer, E. J. Origins and mechanisms of miRNAs and siRNAs. Cell 136, 642–655 (2009)

    CAS  Article  Google Scholar 

  18. 18

    Golden, D. E., Gerbasi, V. R. & Sontheimer, E. J. An inside job for siRNAs. Mol. Cell 31, 309–312 (2008)

    CAS  Article  Google Scholar 

  19. 19

    Czech, B. et al. Hierarchical rules for Argonaute loading in Drosophila . Mol. Cell 36, 445–456 (2009)

    CAS  Article  Google Scholar 

  20. 20

    Geng, C. & Macdonald, P. M. Imp associates with squid and Hrp48 and contributes to localized expression of gurken in the oocyte. Mol. Cell. Biol. 26, 9508–9516 (2006)

    CAS  Article  Google Scholar 

  21. 21

    Wang, L. & Jones, D. L. The effects of aging on stem cell behavior in Drosophila . Exp. Gerontol. 46, 340–344 (2010)

    Article  Google Scholar 

  22. 22

    Boyerinas, B. et al. Identification of let-7-regulated oncofetal genes. Cancer Res. 68, 2587–2591 (2008)

    CAS  Article  Google Scholar 

  23. 23

    Nishino, J., Kim, I., Chada, K. & Morrison, S. J. Hmga2 promotes neural stem cell self-renewal in young but not old mice by reducing p16Ink4a and p19Arf Expression. Cell 135, 227–239 (2008)

    CAS  Article  Google Scholar 

  24. 24

    Zhao, C. et al. MicroRNA let-7b regulates neural stem cell proliferation and differentiation by targeting nuclear receptor TLX signaling. Proc. Natl Acad. Sci. USA 107, 1876–1881 (2010)

    ADS  CAS  Article  Google Scholar 

  25. 25

    Landgraf, P. et al. A mammalian microRNA expression atlas based on small RNA library sequencing. Cell 129, 1401–1414 (2007)

    CAS  Article  Google Scholar 

  26. 26

    Chen, C. et al. Defining embryonic stem cell identity using differentiation-related microRNAs and their potential targets. Mamm. Genome 18, 316–327 (2007)

    CAS  Article  Google Scholar 

  27. 27

    Rybak, A., Fuchs, H., Smirnova, L., Brandt, C., Pohl, E. E., Nitsch, R. & Wulczyn, F. G. A feedback loop comprising lin-28 and let-7 controls pre-let-7 maturation during neural stem-cell commitment. Nature Cell Biol. 10, 987–993 (2008)

    CAS  Article  Google Scholar 

  28. 28

    Melton, C., Judson, R. L. & Blelloch, R. Opposing microRNA families regulate self-renewal in mouse embryonic stem cells. Nature 463, 621–626 (2010)

    ADS  CAS  Article  Google Scholar 

  29. 29

    Iliopoulos, D., Hirsch, H. A. & Struhl, K. An epigenetic switch involving NF-κB, Lin28, let-7 microRNA, and IL6 links inflammation to cell transformation. Cell 139, 693–706 (2009)

    CAS  Article  Google Scholar 

  30. 30

    Boyerinas, B., Park, S. M., Hau, A., Murmann, A. E. & Peter, M. E. The role of let-7 in cell differentiation and cancer. Endocr Relat Cancer 17, F19–F36 (2010)

    CAS  Article  Google Scholar 

  31. 31

    Zhu, H. et al. The Lin28/let-7 axis regulates glucose metabolism. Cell 147, 81–94 (2011)

    CAS  Article  Google Scholar 

  32. 32

    Li, X., Cassidy, J. J., Reinke, C. A., Fischboeck, S. & Carthew, R. W. A microRNA imparts robustness against environmental fluctuation during development. Cell 137, 273–282 (2009)

    CAS  Article  Google Scholar 

  33. 33

    Boylan, K. L. et al. Motility screen identifies Drosophila IGF-II mRNA-binding protein–zipcode-binding protein acting in oogenesis and synaptogenesis. PLoS Genet. 4, e36 (2008)

    Article  Google Scholar 

  34. 34

    Kitadate, Y. et al. Boss/Sev signaling from germline to soma restricts germline-stem-cell-niche formation in the anterior region of Drosophila male gonads. Dev. Cell 13, 151–159 (2007)

    CAS  Article  Google Scholar 

  35. 35

    Sokol, N. S. et al. Drosophila let-7 microRNA is required for remodeling of the neuromusculature during metamorphosis. Genes Dev. 22, 1591–1596 (2008)

    CAS  Article  Google Scholar 

  36. 36

    Caldwell, J. C., Fineberg, S. K. & Eberl, D. F. reduced ocelli encodes the leucine rich repeat protein Pray For Elves in Drosophila melanogaster . Fly 1, 146–152 (2007)

    Article  Google Scholar 

  37. 37

    Hime, G. R., Brill, J. A. & Fuller, M. T. Assembly of ring canals in the male germ line from structural components of the contractile ring. J. Cell Sci. 109, 2779–2788 (1996)

    CAS  PubMed  Google Scholar 

  38. 38

    Harrison, D. A., McCoon, P. E., Binari, R., Gilman, M. & Perrimon, N. Drosophila unpaired encodes a secreted protein that activates the JAK signaling pathway. Genes Dev. 12, 3252–3263 (1998)

    CAS  Article  Google Scholar 

  39. 39

    Bailey, T. L. & Elkan, C. Fitting a mixture model by expectation maximization to discover motifs in biopolymers. Proc. Int. Conf. Intell. Syst. Mol. Biol. 2, 28–36 (1994)

    CAS  PubMed  Google Scholar 

  40. 40

    Schmittgen, T. D. & Livak, K. J. Analyzing real-time PCR data by the comparative C T method. Nature Protocols 3, 1101–1108 (2008)

    CAS  Article  Google Scholar 

  41. 41

    Min, K. J., Yamamoto, R., Buch, S., Pankratz, M. & Tatar, M. Drosophila lifespan control by dietary restriction independent of insulin-like signaling. Aging Cell 7, 199–206 (2008)

    CAS  Article  Google Scholar 

  42. 42

    Yuan, J. S., Reed, A., Chen, F. & Stewart, C. N., Jr Statistical analysis of real-time PCR data. BMC Bioinformatics 7, 85 (2006)

    Article  Google Scholar 

  43. 43

    Brennecke, J. et al. Discrete small RNA-generating loci as master regulators of transposon activity in Drosophila . Cell 128, 1089–1103 (2007)

    CAS  Article  Google Scholar 

  44. 44

    Haley, B. & Zamore, P. D. Kinetic analysis of the RNAi enzyme complex. Nature Struct. Mol. Biol. 11, 599–606 (2004)

    CAS  Article  Google Scholar 

  45. 45

    Haley, B., Foys, B. & Levine, M. Vectors and parameters that enhance the efficacy of RNAi-mediated gene disruption in transgenic Drosophila . Proc. Natl Acad. Sci. USA 107, 11435–11440 (2010)

    ADS  CAS  Article  Google Scholar 

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We are grateful to D. St Johnston, W. Chia, P. Macdonald, R. Carthew, E. Bach, D. Harrison, T. Volk, U. Heberlein, A. Spradling, J. Kadonaga, G. Hannon, T. Hays, N. Sokol, H. Siomi and P. Lasko for reagents and fly stocks, to C. Doe, R. Hans, G. Volohonsky, T. Juven-Gershon, A. Pasquinelli, R. Zhou and S. Aigner for guidance on methods used in this manuscript, to O. Tam for computational support, and to C. Koehler for technical assistance. This work was supported by the G. Harold and Leila Y. Mathers Charitable Foundation, the Ellison Medical Foundation, the Emerald Foundation, the American Federation for Aging Research, and the National Institutes of Health (to D.L.J.). B.C. is supported by a PhD fellowship from the Boehringer Ingelheim Fonds. E.L. is supported by the National Science Foundation.

Author information




H.T., C.D. and D.L.J. designed experiments. H.T. and C.D. performed experiments. B.C. generated and analysed small RNA libraries. E.L. performed bioinformatic analysis to identify Imp-binding sequences. H.T., C.D., B.C. and D.L.J. evaluated the data and wrote the manuscript.

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Correspondence to D. Leanne Jones.

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The authors declare no competing financial interests.

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Toledano, H., D’Alterio, C., Czech, B. et al. The let-7–Imp axis regulates ageing of the Drosophila testis stem-cell niche. Nature 485, 605–610 (2012).

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