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Modulation of dADAR-dependent RNA editing by the Drosophila fragile X mental retardation protein

Nature Neuroscience volume 14, pages 1517–1524 (2011)Cite this article

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Abstract

Loss of FMR1 gene function results in fragile X syndrome, the most common heritable form of intellectual disability. The protein encoded by this locus (FMRP) is an RNA-binding protein that is thought to primarily act as a translational regulator; however, recent studies have implicated FMRP in other mechanisms of gene regulation. We found that the Drosophila fragile X homolog (dFMR1) biochemically interacted with the adenosine-to-inosine RNA-editing enzyme dADAR. Adar and Fmr1 mutant larvae exhibited distinct morphological neuromuscular junction (NMJ) defects. Epistasis experiments based on these phenotypic differences revealed that Adar acts downstream of Fmr1 and that dFMR1 modulates dADAR activity. Furthermore, sequence analyses revealed that a loss or overexpression of dFMR1 affects editing efficiency on certain dADAR targets with defined roles in synaptic transmission. These results link dFMR1 with the RNA-editing pathway and suggest that proper NMJ synaptic architecture requires modulation of dADAR activity by dFMR1.

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Figure 1: dFMR1 biochemically interacts with dADAR in Drosophila S2 cell culture and in vivo.
Figure 2: Adar5G1 mutants exhibit NMJ defects in third instar larvae.
Figure 3: Neuronal expression of dADAR is sufficient for normal NMJ synaptic architecture.
Figure 4: Deaminase activity by dADAR is essential for normal NMJ synaptic architecture.
Figure 5: Adar and Fmr1 genetically interact.
Figure 6: Reduction of Adar dosage rescues the Fmr13 null NMJ defects in L3 larvae.
Figure 7: dFMR1 modifies dADAR function and affects A-to-I editing efficiency.

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Acknowledgements

We thank current and former members of the Jongens laboratory for helpful discussions and technical support, especially R. Beerman for preliminary studies with the LMB experiments, and S. Cruz and C. Dubowy. We also thank M. Sundaram and D. Hancks for critical reading of the manuscript. We are grateful to R. Carstens, G. Bashaw, T. Dockendorff, C. Hughes, K. Kaestner, S. Artavanis-Tsakonas, the Bloomington Stock Center and the Developmental Studies Hybridoma Bank for fly strains and reagents. We also thank C.-X. Yuan and The Perelman School of Medicine at the University of Pennsylvania Proteomics Facility for help with the mass spectrometry results. This work was supported by a Predoctoral Training grant in Genetics (5T32GM008216 to B.B.), a National Institute of Mental Health grant (MH086705 to T.A.J.), a National Institute of General Medical Science grant (GM086902 to T.A.J.) and an Ellison Medical Foundation Senior Scholar award to R.A.R.

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Authors and Affiliations

  1. Department of Genetics, The Perelman School of Medicine at the University of Pennsylvania, Philadelphia, Pennsylvania, USA

    Balpreet Bhogal, Anita S-R Pepper & Thomas A Jongens

  2. Department of Molecular Biology, Cell Biology and Biochemistry, Brown University, Providence, Rhode Island, USA

    James E Jepson, Yiannis A Savva & Robert A Reenan

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  1. Balpreet Bhogal
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Contributions

B.B. performed the experiments shown in Figures 1,2,3,4,5,6 and 7 and Supplementary Figures 2–5, generated the figures and wrote the manuscript. J.E.J. and Y.A.S. generated the Adar-HA4.5.2 and Adar-HA12.5.2 fly lines used in this study, performed experiments shown in Figure 7, helped generate the figure and contributed to the writing of this manuscript. J.E.J. also performed experiments for, and generated part of, Supplementary Figure 4. A.S.-R.P. performed the experiments shown in Supplementary Figure 1, generated the figure, identified the initial findings for this manuscript and contributed to the writing of this manuscript. R.A.R. and T.A.J. contributed to the conclusions drawn from all figures, provided intellectual input, contributed portions of the funding and contributed to the writing of this manuscript.

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Correspondence to Thomas A Jongens.

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Bhogal, B., Jepson, J., Savva, Y. et al. Modulation of dADAR-dependent RNA editing by the Drosophila fragile X mental retardation protein. Nat Neurosci 14, 1517–1524 (2011). https://doi.org/10.1038/nn.2950

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