Abstract

Coding variants in the triggering receptor expressed on myeloid cells 2 (TREM2) are associated with late-onset Alzheimer’s disease (AD). We demonstrate that amyloid plaque seeding is increased in the absence of functional Trem2. Increased seeding is accompanied by decreased microglial clustering around newly seeded plaques and reduced plaque-associated apolipoprotein E (ApoE). Reduced ApoE deposition in plaques is also observed in brains of AD patients carrying TREM2 coding variants. Proteomic analyses and microglia depletion experiments revealed microglia as one origin of plaque-associated ApoE. Longitudinal amyloid small animal positron emission tomography demonstrates accelerated amyloidogenesis in Trem2 loss-of-function mutants at early stages, which progressed at a lower rate with aging. These findings suggest that in the absence of functional Trem2, early amyloidogenesis is accelerated due to reduced phagocytic clearance of amyloid seeds despite reduced plaque-associated ApoE.

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The data that support the findings of this study are available from the corresponding author upon reasonable request.

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Acknowledgements

This work was supported by the Deutsche Forschungsgemeinschaft (DFG) within the framework of the Munich Cluster for Systems Neurology (EXC 1010 SyNergy), a DFG funded Koselleck Project (HA1737/16-1 to C.H.), by the Helmholtz-Gemeinschaft Zukunftsthema ‘Immunology and Inflammation’ (ZT-0027 to C.H.), the FOR2290 (to S.F.L. and C.H.), and by a dedicated PET imaging grant to M.B. and A.R. (BR4580/1-1 & RO5194/1-1). This project has received additional funding from the Innovative Medicines Initiative 2 Joint Undertaking under grant agreement No. 115976. Startup funding for this project came from LMUexcellent. Additional funding came from the general legacy of S. Ammer, the MetLife award, and the Cure Alzheimer’s fund. M.M.-L. is supported by the Emmy Noether Program of the DFG (ME 3542/1-1). M.M.-L. and S.F.L. are supported by the Hans and Ilse Breuer Foundation. S.T. got support from Ono Pharmaceuticals, Japan. D.M.H. is supported by NIH grants NS090934 and AG047644, the JPB Foundation, and the Cure Alzheimer’s Fund. S.F.L. is supported by the Centers of Excellence in neurodegeneration and the Helmholtz-Israel program. O.B. is supported by NIH grants NINDS (R01NS088137), NIH-NIA (R01AG051812), NIH-NIA (R01AG054672) and the Cure Alzheimer’s Fund. The APPPS1 colony was established from a breeding pair kindly provided by M. Jucker (Hertie-Institute for Clinical Brain Research, University of Tübingen and DZNE-Tübingen). The authors thank M. Colonna for the Trem2–/– mice. Thanks to the Queen Square Brain Bank for access to tissue: this resource is funded in part by the Weston Foundation and the MRC. D.E. is supported by the European Community’s Health Seventh Framework Programme under grant agreement 617198 [DPR-MODELS].

Author information

Author notes

    • Axel Rominger

    Present address: Department of Nuclear Medicine, Inselspital, University Hospital Bern, Bern, Switzerland

Affiliations

  1. Chair of Metabolic Biochemistry, Biomedical Center (BMC), Faculty of Medicine, Ludwig-Maximilians-Universität München, Munich, Germany

    • Samira Parhizkar
    • , Gernot Kleinberger
    • , Brigitte Nuscher
    • , Michael Willem
    • , Nadine Pettkus
    •  & Christian Haass
  2. Munich Cluster for Systems Neurology (SyNergy), Munich, Germany

    • Thomas Arzberger
    • , Gernot Kleinberger
    • , Stefan F. Lichtenthaler
    • , Jochen Herms
    • , Peter Bartenstein
    • , Dieter Edbauer
    • , Axel Rominger
    •  & Christian Haass
  3. German Center for Neurodegenerative Diseases (DZNE) Munich, Munich, Germany

    • Thomas Arzberger
    • , Stefan F. Lichtenthaler
    • , Stephan A. Müller
    • , Alessio Colombo
    • , Laura Sebastian Monasor
    • , Sabina Tahirovic
    • , Jochen Herms
    • , Dieter Edbauer
    •  & Christian Haass
  4. Center for Neuropathology and Prion Research, Ludwig-Maximilians-Universität München, Munich, Germany

    • Thomas Arzberger
    •  & Jochen Herms
  5. Department of Psychiatry and Psychotherapy, Ludwig-Maximilians-Universität München, Munich, Germany

    • Thomas Arzberger
  6. Department of Nuclear Medicine, University Hospital, Ludwig-Maximilians-Universität München, Munich, Germany

    • Matthias Brendel
    • , Maximilian Deussing
    • , Carola Focke
    • , Peter Bartenstein
    •  & Axel Rominger
  7. Department of Neurology, Hope Center for Neurological Disorders, and Charles F. and Joanne Knight Alzheimer’s Disease Research Center, Washington University School of Medicine, St. Louis, MO, USA

    • Monica Xiong
    •  & David M. Holtzman
  8. Institute for Stroke and Dementia Research, Klinikum der Universität München, Munich, Germany

    • Alireza Ghasemigharagoz
    •  & Ali Ertürk
  9. Department of Neurology, Medical Center University of Freiburg, and Faculty of Medicine, University of Freiburg, Freiburg, Germany

    • Natalie Katzmarski
    •  & Melanie Meyer-Luehmann
  10. Ann Romney Center for Neurologic Diseases, Department of Neurology, Brigham and Women´s Hospital, Harvard Medical School, Boston, MA, USA

    • Susanne Krasemann
    •  & Oleg Butovsky
  11. Institute of Neuropathology, University Medical Center Hamburg-Eppendorf, Hamburg, Germany

    • Susanne Krasemann
  12. Neuroproteomics, School of Medicine, Klinikum Rechts der Isar, Technische Universität München, Munich, Germany

    • Stefan F. Lichtenthaler
    •  & Stephan A. Müller
  13. Institute for Advanced Study, Technische Universität München, Garching, Germany

    • Stefan F. Lichtenthaler
  14. Evergrande Center for Immunologic Diseases, Brigham and Women’s Hospital, Harvard Medical School, Boston, MA, USA

    • Oleg Butovsky
  15. Department of Cellular Neurology, Hertie Institute for Clinical Brain Research, University of Tübingen, Tübingen, Germany

    • Stefan A. Grathwohl
    •  & Jonas J. Neher
  16. German Center for Neurodegenerative Diseases (DZNE) Tübingen, Tübingen, Germany

    • Jonas J. Neher

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Contributions

C.H., M.M.-L., G.K., and S.P. conceived the study and analyzed the results. C.H. wrote the manuscript with help from M.M.-L., S.P., T.A., G.K., M.B., and D.M.H. and further input from all co-authors. S.P. and N.K. performed seeding experiments; S.P. and M.X. performed the ApoE stainings. B.N. performed Aβ ELISA. M.B., M.D., C.F., P.B., and A.R. performed PET imaging and quantitative PET analyses. G.E. made GE180 cassettes available through an early access model. A.E., A.G. and S.P. performed the three-dimensional image analyses. O.B. and S.K. provided independent immunohistochemical data and interpretation on ApoE. D.M.H. interpreted the ApoE stainings and provided appropriate ApoE antibodies. T.A. and J.H. provided human brain sections and interpreted the immunohistochemical analyses. G.K. and N.P. performed TREM2 sequencing and D.E. performed PSEN1, PSEN2 and APP sequencing of human autopsy cases. S.T., A.C., L.S.M., S.A.M., and S.F.L. prepared primary microglial lysates and measured ApoE levels by mass spectrometry. M.W. provided technical advice for protein extraction and ApoE experiments. S.A.G. and J.J.N. provided brain sections from microglia-depleted mice.

Competing interests

C.H. collaborates with Denali and received a speaker honorarium of Roche and Novartis. D.M.H. co-founded and is on the scientific advisory board of C2N Diagnostics. D.M.H. consults for Denali, Eli Lilly, Glaxosmithkline, and AbbVie. A.R. received consultant and speaker honoria from Piramal Imaging and GE Healthcare. O.B. collaborates with Sanofi. S.T. collaborates with Ono Pharmaceuticals (Japan). S.A.G is an employee of Neurimmune AG. All other authors declare no competing interests.

Corresponding authors

Correspondence to Melanie Meyer-Luehmann or Christian Haass.

Integrated supplementary information

  1. Supplemetary Figure 1 Amyloid seeding occurs in a host-dependent manner.

    a, Top: ThioS and 4G8 co-staining for amyloid plaques in C57BL6 mice injected with APPPS1 brain homogenate (BH) (n = 7 mice) show no plaques in the hippocampus or cortex ten weeks after injection. Middle: In contrast, amyloid seeding is induced in the hippocampus of APPPS1/Trem2+/+ mice at four months (n = 8 mice). Bottom: Age-matched C57BL6 brain homogenate-injected APPPS1 mice did not induce amyloid seeding in the hippocampus, although cortical plaques are present in the transgenic APPPS1 mice (n = 6 mice). b, Quantification of Aβ42 in formic acid fractions of C57BL6 brain homogenate-injected hippocampi by Meso Scale Discovery electrochemiluminescence assay confirm significantly lower plaque load compared to APPPS1 brain homogenate-injected hippocampi in APPPS1/Trem2+/+ mice at four months. Data represent mean ± s.e.m. (APPPS1 BH-injected C57BL6 n = 6 mice, C57BL6 BH-injected APPPS1/Trem2+/+ n = 6 mice; APPPS1-injected APPPS1/Trem2+/+ n = 8 mice; F2,17 = 36.8, P = 1.1 × 10–5). One-way ANOVA, Dunnett’s post hoc analysis; ***P < 0.0001. c, APPPS1 brain homogenate-injected APPPS1/Trem2+/+, APPPS1/Trem2-/- and APPPS1/Trem2p.T66M mice show no hippocampal or cortical plaque staining two weeks after injection (n = 4 mice/genotype). d, Uninjected APPPS1/Trem2+/+ mice show neither ThioS nor immunopositive amyloid plaques in hippocampus compared to cortex. Similar seeding patterns are not observed in the cortex because amyloid seeding is region-dependent2 but note pre-existing non-experimentally seeded plaques within the cortex of four months old transgenic mice. Similarly, uninjected APPPS1/Trem2-/- and APPPS1/Trem2p.T66M mice show no ThioS or 4G8-positive plaques in the hippocampus compared to cortex (n = 6 mice/genotype).

  2. Supplemetary Figure 2 Trem2 deficiency impairs microglial clustering and CD68 upregulation around cortical plaques.

    a, APPPS1/Trem2+/+ mice show increased microglia clustering around cortical plaques as compared to APPPS1/Trem2-/- and APPPS1/Trem2p.T66M mice. b, Number of IBA1-positive microglia cells quantified per plaque in the cortex (n+/+ = 9 mice, n-/- = 10 mice, np.T66M = 10 mice, F2,26 = 83.07, P = 5.1 × 10–12). c, APPPS1/Trem2+/+ mice show increased CD68-positive microglia clustering around cortical plaques as compared to APPPS1/Trem2-/- and APPPS1/Trem2p.T66M mice. d, Number of CD68-positive microglia cells quantified per plaque in the cortex (n+/+ = 8 mice, n-/- = 6 mice, np.T66M = 6 mice; F2,17 = 109.7, P = 1.9 × 10–10). e, Number of IBA1-positive microglia cells quantified in plaque barren thalamic nuclei (n = 6 mice/genotype; F2,15 = 0.1553, P = 0.8576). Data represent mean ± s.e.m.. One-way ANOVA, Dunnett’s post hoc analysis; n.s. P > 0.05; ***p < 0.0001.

  3. Supplemetary Figure 3 Regression correlation analysis with longitudinal imaging of microglial activity as well as fibrillar amyloidogenesis in individual mice.

    a,b, Coronal and axial slices show serial TSPO (a) and Amyloid μPET (b) Z-score increases (versus C57BL6) from three to twelve months of age for APPPS1/Trem2+/+ and APPPS1/Trem2-/- mice. APPPS1/Trem2-/- mice indicate decreased microglial activity, most pronounced at twelve months of age, and higher fibrillar amyloidogenesis at three and six months of age when compared to APPPS1/Trem2+/+ mice. c,d, Spaghetti plots show individual longitudinal time courses of cortical microglial activity (c) and fibrillar amyloidogenesis (d) as assessed by in vivo μPET in APPPS1/Trem2+/+ (purple highlighted data point corresponds to representative image shown in e and f) and APPPS1/Trem2-/- mice (dark blue highlighted data point corresponds to representative image shown in a and b). e,f, x34/CD68/IBA1 co-stained microglia (n+/+ = 8 mice; n-/- = 7 mice) as well as (e) fibrillar and immunostained amyloid plaques (f) (n+/+ = 8 mice; n-/- = 7 mice) of twelve months old APPPS1 mice previously included in longitudinal TSPO and Amyloid μPET imaging. g,h, Regression correlation analysis of CD68-positive phagocytic microglia staining and TSPO μPET imaging (n+/+ = 5 mice, n-/- = 4 mice, P = 0.0026) (g) and x34-positive fibrillar Aβ staining and amyloid μPET imaging (n+/+ = 4 mice, n-/- = 4 mice, P = 0.0003) (h)in three months old APPPS1 mice. i,j, Regression correlation analysis of CD68 and TSPO μPET imaging (n+/+ = 10 mice, n-/- = 5 mice, p = 5.2E-5) (i)and x34 and Amyloid μPET imaging (n+/+ = 4 mice, n-/- = 4 mice, P = 0.0088) (j)in six months old APPPS1 mice. k,l Regression correlation analysis of CD68 and TSPO μPET imaging (n+/+ = 8 mice, n-/- = 7 mice, P = 1.0 x 10-6) (k) and x34 and Amyloid μPET imaging (n+/+ = 7 mice, n-/- = 7 mice, P = 2.0 × 10–5) (l) in twelve months old APPPS1 mice. Purple dots represent APPPS1/Trem2+/+ and blue dots indicate APPPS1/Trem2-/- mice.

  4. Supplemetary Figure 4 Confocal images of individual microglia-depleted APPPS1/TK+ and control APPPS1/TK mice.

    a, IMARIS 3D reconstructed high-resolution confocal images of x34/ApoE/Aβ stained cortical amyloid plaques of control APPPS1/TK- (left) and age-matched microglia-depleted APPPS1/TK + mice (right) (n = 3 mice/genotype). Numbers at the top left of each image indicate three individual mice per group. b, Left: 3D reconstructed image of x34/ApoE/IBA1 staining shows higher ApoE and IBA1 colocalisation in APPPS1/TK- mice indicated by the degree of white merged staining, compared to; right: APPPS1/TK + mice (n = 3 mice/genotype). c, x34/ApoE/GFAP co-staining in APPPS1/TK- mice looks comparable to APPPS1/TK + mice (n = 3 mice/genotype).

  5. Supplemetary Figure 5 Reduced ApoE levels in Aβ plaques and impaired microglial clustering in TREM2 mutation carriers.

    a, Temporal neocortex of additional human AD patients with and without the indicated examples of TREM2 variants stained for Aβ by 4G8 immunohistochemistry. b, Reduced ApoE immunoreactivity within amyloid plaques compared to no CV shown in sections consecutive to those of the left column. Red boxes indicate the area in each staining that is magnified as inset. c, Additional examples of ApoE stainings comparing the same region in consecutive Aβ stained sections. d, Impaired clustering of microglial cells (brown) around and within amyloid plaques (red) in AD cases with different TREM2 coding variants compared to no CV cases (last 2 rows). Dotted black boxes indicate the area magnified as inset. e, Quantification of Aβ42 in formic acid fractions of temporal neocortex by Meso Scale Discovery electrochemiluminescence assay (nR47H = 2 cases, nR62H = 4 cases; nR62C = 1 case; nno CV = 4 cases). f, ApoE/Aβ42 ratio quantified from temporal neocortex plaque-enriched formic acid fraction (nR47H = 2 cases, nR62H = 4 cases; nR62C = 1 case, nno CV = 4 cases). Of note, frozen material from p.D87N cases was not available and therefore not included. One of the no CV cases could not be included in the study due to diagnosed Hepatitis. (g) Number of IBA1-positive microglia per plaque in temporal neocortex quantified from images shown in d and Fig. 8 (nR47H = 2 cases, nR62H = 4 cases; nR62C = 1 case; nD87N = 2 cases; nno CV = 3 cases). Noteworthy, sections from only three no CV cases were available in comparison to frozen material. No subjects were excluded in this analysis. (h) Aβ42 in formic acid fractions quantified from temporal neocortex grouped according to APOE status (nE3/E3 = 4 cases, nE3/E4 = 4 cases; nE4/E4 = 3 cases). (i) Number of IBA1-positive microglia per plaque in temporal neocortex grouped according to APOE status (nE3/E3 = 3 cases, nE3/E4 = 6 cases; nE4/E4 = 3 cases). Medial temporal cortex at the level of anterior hippocampus was used for all experiments. Data represent as mean ± s.d.

  6. Supplemetary Figure 6 Schematic summary.

    Schematic figure of the consequences of a Trem2 loss-of-function (LoF) on microglial clustering and ApoE accumulation in amyloid plaques.

  7. Supplemetary Figure 7 Original western blots.

    Cropped KODAK films for Western blots in Fig. 1, Fig.4, Fig. 5, Fig. 6 and Fig. 8. Membranes were cut prior to antibody stainings to allow for detection of proteins running at different sizes on the same membrane.

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https://doi.org/10.1038/s41593-018-0296-9

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