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Increased synapse elimination by microglia in schizophrenia patient-derived models of synaptic pruning

Abstract

Synapse density is reduced in postmortem cortical tissue from schizophrenia patients, which is suggestive of increased synapse elimination. Using a reprogrammed in vitro model of microglia-mediated synapse engulfment, we demonstrate increased synapse elimination in patient-derived neural cultures and isolated synaptosomes. This excessive synaptic pruning reflects abnormalities in both microglia-like cells and synaptic structures. Further, we find that schizophrenia risk-associated variants within the human complement component 4 locus are associated with increased neuronal complement deposition and synapse uptake; however, they do not fully explain the observed increase in synapse uptake. Finally, we demonstrate that the antibiotic minocycline reduces microglia-mediated synapse uptake in vitro and its use is associated with a modest decrease in incident schizophrenia risk compared to other antibiotics in a cohort of young adults drawn from electronic health records. These findings point to excessive pruning as a potential target for delaying or preventing the onset of schizophrenia in high-risk individuals.

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Fig. 1: Characterizations of iMG cells.
Fig. 2: Isolation of active synaptic structures from iPSC-derived neural cultures.
Fig. 3: Increased engulfment of synaptic structures in schizophrenia-derived models.
Fig. 4: Microglial factors influence synapse engulfment.
Fig. 5: C4 SZ risk variants increase complement deposition on neurons and increase synapse engulfment in in vitro models derived from SZ patients.
Fig. 6: Minocycline inhibits synapse engulfment in vitro and decreases SZ risk in EHRs.

Data availability

Gene expression data is available for download from the NCBI Gene Expression Omnibus (GEO) at SuperSeries (NCBI GEO no. GSE123349). Additional data supporting the findings of this study are available from the corresponding authors upon reasonable request.

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Acknowledgements

We thank the study participants. We are also grateful to J. Ruiliera (MGH) for technical assistance with isolating buffy coats, D. Fletcher and S. Kommineni (Novartis) for stem cell reprogramming and automated neural differentiation assistance. This work was supported by grant no. P50-MH106933 (National Institute of Mental Health and National Human Genome Research Institute) and an anonymous donor to R.H.P., grant nos. 2017-02559 (Swedish Research Council) and MMW 2017.0118 (Marianne and Marcus Wallenberg Foundation) to C.M.S., and a National Institute of Mental Health Biobehavioral Research Award for Innovative New Scientists (BRAINS) no. R01MH113858 to R.K.

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C.M.S., S.D.S., C.P.G. (C3 deposition assay), and R.H.P. conceived the research. C.M.S., S.D.S., and R.H.P. contributed to the overall design, direction, and reporting of the study. J.G. and T.F. derived the neural cultures. C.M.S. and J.G., with help from J.M.T., generated the induced microglia, isolated the SYNs, and performed all experiments as well as data analyses unless otherwise specified. B.W., J.G., and R.K. performed the coculture experiments. J.W., C.M.S., and J.G. performed the data analyses of the images required using the IncuCyte ZOOM live imaging system. J.G. and J.M.T. performed the Western blot experiments. K.W. and A.K. constructed the inducible NGN2 TALEN plasmid constructs and developed the automated cortical excitatory neuronal differentiation and characterization. C.P.G., with help from J.D.B. and P.B.W., designed and performed the C4 deposition assays and performed the molecular analyses of the C4 alleles. C.P.G. and C.M.S. analyzed the C4 allele data. S.D.S. provided cell reprogramming expertise and R.H.P. performed the analyses using EHRs. All authors discussed the results and implications and commented on the manuscript at various stages.

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Correspondence to Carl M. Sellgren or Roy H. Perlis.

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Competing interests

C.P.G., A.K., K.W., P.B.W., and J.D.B. are employees of Novartis. R.H.P. has served on the scientific advisory boards of Genomind and Psy Therapeutics, and was a consultant to RID Ventures and Takeda (none related to the present work). C.M.S. discloses lecture and consulting fees from Otsuka Pharmaceutical and H. Lundbeck A/S (none related to the present work). None of the other authors declare any competing interests.

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Sellgren, C.M., Gracias, J., Watmuff, B. et al. Increased synapse elimination by microglia in schizophrenia patient-derived models of synaptic pruning. Nat Neurosci 22, 374–385 (2019). https://doi.org/10.1038/s41593-018-0334-7

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