Abstract
The microtubule cytoskeleton forms complex macromolecular assemblies with a range of microtubule-associated proteins (MAPs) that have fundamental roles in cell architecture, division and motility. Determining how an individual MAP modulates microtubule behaviour is an important step in understanding the physiological roles of various microtubule assemblies. To characterize how MAPs control microtubule properties and functions, we developed an approach allowing for medium-throughput analyses of MAPs in cell-free conditions using lysates of mammalian cells. Our pipeline allows for quantitative as well as ultrastructural analyses of microtubule–MAP assemblies. Analysing 45 bona fide and potential mammalian MAPs, we uncovered previously unknown activities that lead to distinct and unique microtubule behaviours such as microtubule coiling or hook formation, or liquid–liquid phase separation along the microtubule lattice that initiates microtubule branching. We have thus established a powerful tool for a thorough characterization of a wide range of MAPs and MAP variants, thus opening avenues for the determination of mechanisms underlying their physiological roles and pathological implications.
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Data availability
The cryo-EM map for EML1–GFP bound to a microtubule has been deposited in the Electron Microscopy Data Bank (EMDB) under the accession code EMD-32033. Gene sequences of newly identified MAPs (DCX_L, MAP11; Supplementary Table 1) have been deposited at GenBank under the accession codes OK539808 (DCX_L) and OK539809 (MAP11). Deposited data are listed in Supplementary Table 5. All commercial resources used here are detailed in Supplementary Table 3; primers for molecular cloning are listed in Supplementary Table 1; antibodies are listed in Supplementary Table 4. All data supporting the findings of this study are available from the corresponding author upon reasonable request. Source data are provided with this paper.
Code availability
Free software was used for most of the analyses and details of paid software are included in Supplementary Table 3. Home-made macros used in the analyses (Fig. 7d,g) have been deposited at Zenodo (https://doi.org/10.5281/zenodo.5648066).
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Acknowledgements
This work was supported by the ANR-10-IDEX-0001-02, the LabEx Cell’n’Scale ANR-11-LBX-0038 and the Institut de convergence Q-life ANR-17-CONV-0005. C.J. is supported by the Institut Curie, the French National Research Agency (ANR) awards ANR-12-BSV2-0007 and ANR-17-CE13-0021, the Institut National du Cancer (INCA) grant 2014-PL BIO-11-ICR-1, and the Fondation pour la Recherche Medicale (FRM) grant DEQ20170336756. A.S.J. was supported by the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement no. 675737, and the FRM grant FDT201904008210. S.B. was supported by the FRM grant FDT201805005465. M.S. acknowledges funding support from DBT/Wellcome Trust India Alliance Intermediate Fellowship (IA/I/14/2/501533), EMBO Young Investigator Programme award, CEFIPRA (5703-1), Department of Science and Technology, SERB-EMR grant (CRG/2019/003246) and DBT-BIRAC (BT/PR40389/COT/142/6/2020). The authors acknowledge the National Cryo-EM Facility at Bangalore Life Science Cluster, Bangalore, India and the funding by B-life grant from Department of Biotechnology (DBT/PR12422/MED/31/287/2014). M.M.M. is supported by the Fondation Vaincre Alzheimer grant FR-16055p. We thank the team of T. Surrey for technical advice and training; L. Kainka, F. Lautenschläger and G. M. Montalvo Bereau for experimental support; S. Citi, F. Francis, D. Gerlich, N. Manel, and C. Nahmias for providing essential reagents; C. Messaoudi, M.-N. Soler and C. Lovo from the Multimodal Imaging Center (MIC; CNRS UMR2016 / Inserm US43) for support with imaging and image analyses; K. R. Vinothkumar for help with EM data collection and deposition of the maps; and T. Müller-Reichert and P. Tran for insightful discussions and advice.
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A.S.J. established the lysate-based pipeline and performed all experiments related to it. Lysate experiments shown in Extended Data Fig. 10 and Supplementary Video 19 were performed by M.G. S.B., F.M. and V.H. performed molecular cloning and sequence analyses with the help of J.A.S. and M.G. S.B. performed all cell biology experiments. S.B. and V.S. performed live-cell imaging experiments. M.G. purified proteins and established quantitative approaches with A.S.J. M.B. performed electron microscopy studies and analyses. A.S.J. and L.B. analysed and quantified imaging data with the help of S.B. A.S.J., S.B. and C.J. analysed data and prepared figures and videos with the help of M.B. and L.B. M.S. supervised electron microscopy studies and analyses. C.J. supervised the study with the help of M.M.M. A.S.J., S.B., M.M.M., M.S. and C.J. acquired funding. A.S.J., S.B. and C.J. wrote the manuscript with the help of M.G., M.B., M.M.M. and M.S.
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Extended data
Extended Data Fig. 1 Schematic representation of the SLIC cloning approach (complement to Fig. 1).
a, Schematic representation (SnapGene® map) of the principal cloning vector used in this study, pTRIP, which is designed for the generation of lentivirus74, but can also be used to transiently transfect cells as done in our study. Zoom images show two possible insertion points of coding sequence for either amino- or carboxy-terminal tagging with GFP. Primer overhang sequences shown here were completed with the forward and reverse sequences from the open reading frame of the coding sequence (see Supplementary Table 1). Note that the P2A site after the GFP sequence is discarded when MAPs are cloned with an amino-terminal GFP tag. A similar vector with mCherry instead of GFP was used for experiments in which two MAPs are visualised concomitantly. b, Schematic representation of the SLIC cloning procedure23. Step 1: amplification of open reading frames of proteins of interest; digestion of plasmid vector with appropriate enzymes for amino- or carboxy-terminal tagging (a). Step 2: treatment of plasmid and PCR product with T4 polymerase without dNTPs. Under these conditions, the 3’ exonuclease activity of the enzyme generates single-strand overhangs on both, PCR product and plasmid. Step 3: transformation into competent E. coli cells, which will fuse PCR product and plasmid using endogenous DNA repair mechanism23. Step 4: plasmid DNA from single bacteria colonies is extracted and verified by enzymatic digestion and subsequent sequencing. We identified alternative splice isoforms for: DCLK1, MAP2, MAP4, SNPH, Tau, and so-far non-described isoforms for DCX (called here DCX_L) and MAP11. Accession numbers, ORF size, position of the fluorescent tag, and PCR primers are listed in Supplementary Table 1, and are also schematically represented in Fig. 2c.
Extended Data Fig. 2 Systematic characterisation of the intracellular behaviour of 45 MAP candidates (complement to Fig. 2a,c).
Representation of all 45 GFP-tagged MAPs, or presumed MAPs (Supplementary Table 1), expressed in U-2 OS cells. MAPs with strong expression levels were fixed after 24 h for immunostaining, while weakly expressed MAPs were fixed after 48 h. Cells were stained with anti-α-tubulin antibody 12G10. Separate images for tubulin and the GFP are shown in Supplementary Fig. 1. All proteins analysed here were classified into three distinct categories (Fig. 2a,c). Details of the experimental repeats and number of cells are provided as source data and in the Statistics & Reproducibility section. Numerical data are available in source data.
Extended Data Fig. 3 Characterisation of the behaviour of selected GFP-MAPs with growing microtubules in cell lysates (complement to Fig. 2b,c; see also Supplementary Fig. 2; Supplementary Videos 2a,3d,7b,c).
Lysates of HEK 293 cells expressing GFP-tagged MAP candidates: a, control, b, CSAP, c, MACF1(C1023), d, MACF2(C1079). Frames from videos observed by TIRF microscopy to visualise the dynamic decoration of growing microtubules by GFP-MAPs. Microtubule (MT) seeds are shown in green and GFP-MAPs in white (left panels). At the end of the time-lapse imaging (12 min), microtubules and actin are visualised with YL1/2 antibody and SiR-actin, respectively, allowing to determine whether a MAP associates with microtubules alone, or co-aligns microtubules and actin fibres in the lysate (right panels). All experiments were performed under equivalent conditions. To determine whether actin polymerisation played a role in the observed microtubule-MAP interactions, all experiments were performed using the same lysates and equivalent conditions in the presence of 11 µM of Latrunculin A to prevent actin polymerisation31,32. Details of the experimental repeats are provided as source data and in the Statistics & Reproducibility section. Numerical data are available in source data.
Extended Data Fig. 4 Characterisation of the behaviour of selected GFP-MAPs with growing microtubules in cell lysates (complement to Fig. 2c; see also Supplementary Fig. 2, Supplementary Video. 5).
Lysates of HEK 293 cells expressing GFP-tagged MAP candidates: a, EML1, b, EML2, c, EML3, d, EML4. Frames from videos observed by TIRF microscopy to visualise the dynamic decoration of growing microtubules by GFP-MAPs. Microtubule (MT) seeds are shown in green and GFP-MAPs in white (left panels). At the end of the time-lapse imaging (12 min), microtubules and actin are visualised with YL1/2 antibody and SiR-actin, respectively, allowing to determine whether a MAP associates with microtubules alone, or co-aligns microtubules and actin fibres in the lysate (right panels). All experiments were performed under equivalent conditions. To determine whether actin polymerisation played a role in the observed microtubule-MAP interactions, all experiments were performed using the same lysates and equivalent conditions in the presence of 11 µM of Latrunculin A to prevent actin polymerisation31,32. Details of the experimental repeats are provided as source data and in the Statistics & Reproducibility section. Numerical data are available in source data.
Extended Data Fig. 5 Characterisation of the behaviour of selected GFP-MAPs with growing microtubules in cell lysates (complement to Fig. 2c; see also Supplementary Fig. 2; Supplementary Video 9).
Lysates of HEK 293 cells expressing GFP-tagged MAP candidates: a, MAP7, b, MAP7D1, c, MAP7D2, d, MAP7D3. Frames from videos observed by TIRF microscopy to visualise the dynamic decoration of growing microtubules by GFP-MAPs. Microtubule (MT) seeds are shown in green and GFP-MAPs in white (left panels). At the end of the time-lapse imaging (12 min), microtubules and actin are visualised with YL1/2 antibody and SiR-actin, respectively, allowing to determine whether a MAP associates with microtubules alone, or co-aligns microtubules and actin fibres in the lysate (right panels). All experiments were performed under equivalent conditions. To determine whether actin polymerisation played a role in the observed microtubule-MAP interactions, all experiments were performed using the same lysates and equivalent conditions in the presence of 11 µM of Latrunculin A to prevent actin polymerisation31,32. Details of the experimental repeats are provided as source data and in the Statistics & Reproducibility section. Numerical data are available in source data.
Extended Data Fig. 6 Characterisation of the behaviour of selected GFP-MAPs with growing microtubules in cell lysates (complement to Fig. 2c; see also Supplementary Fig. 2; Supplementary Video 7d,8a,12c,d).
Lysates of HEK 293 cells expressing GFP-tagged MAP candidates: a, MAP2C, b, MAP2D, c, Tau(0N-3R), d, Tau(0N-4R). Frames from videos observed by TIRF microscopy to visualise the dynamic decoration of growing microtubules by GFP-MAPs. Microtubule (MT) seeds are shown in green and GFP-MAPs in white (left panels). At the end of the time-lapse imaging (12 min), microtubules and actin are visualised with YL1/2 antibody and SiR-actin, respectively, allowing to determine whether a MAP associates with microtubules alone, or co-aligns microtubules and actin fibres in the lysate (right panels). All experiments were performed under equivalent conditions. To determine whether actin polymerisation played a role in the observed microtubule-MAP interactions, all experiments were performed using the same lysates and equivalent conditions in the presence of 11 µM of Latrunculin A to prevent actin polymerisation31,32. Details of the experimental repeats are provided as source data and in the Statistics & Reproducibility section. Numerical data are available in source data.
Extended Data Fig. 7 Quantification of unique activities of MAPs on growing microtubules (complement to Fig. 3).
a, Inverted grey-scale TIRF images of CSAP-GFP-decorated microtubules, showing that CSAP induces microtubule helices / coils, as well as straight microtubules. Red dashes in the images show where the measurements of the width of the microtubule coils were taken. The diagram (also shown in Fig. 3c) shows a plot of all 41 measurements, with a mean coil width of 872 nm (± s.d.: 125 nm). The quantification was performed from n = 4 independent TIRF assays using 3 independent cell lysate preparations. Data are presented as scatter plots with mean ± s.d.. b, Inverted grey-scale TIRF images of MACF1(C1023)-GFP-decorated microtubules, showing the induction of microtubule hooks. Two red arrow heads show where individual measurements of the diameters of the microtubule hooks were taken. The plot (also shown in Fig. 3d) shows all 136 measurements, with a mean hook diameter of 1.025 µm (± s.d.: 0.15 µm). The quantification was performed from n = 3 independent TIRF assays. Data are presented as scatter plots with mean ± s.d.. c, Inverted grey-scale TIRF images of two zoomed time series of GFP-MAP2C. In the first time series, GFP-MAP2C reveals the formation of transitional hooks that were fainter than the microtubules, suggesting that they could consist of some protofilaments decorated by GFP-MAP2C. These filaments appeared to initiate the formation of a GFP-MAP2C cluster. The cluster remains attached to the microtubule (MT), which subsequently continues growing. In the second series, a hook-like structure at the growing microtubule (MT) end is converted into a GFP-MAP2C cluster, which however arrests microtubule growth. Note that the fluorescence intensity of both GFP-MAP2C clusters increases continuously, suggesting an accumulation of GFP-MAP2C. The time-lapse shown here is a representative experiment from n = 7 independent TIRF assays using 4 independent set of cell lysates. Numerical data are available in source data.
Extended Data Fig. 8 The impact of a disease-related mutation of EML1 on microtubule binding (complement to Fig. 5; Supplementary Video 16b).
Time-lapse images of microtubules polymerising in a 1:1 mixture of lysates from HEK 293 cells expressing wild-type EML1-mCherry and EML1(T243A)-GFP, respectively. Note that the behaviour of wild-type and mutated EML1 is similar to the observations in (Fig. 5b) despite the inversion of the fluorescence tags. N = 3 independent TIRF assays from one set of cell lysate preparations. Numerical data are available in source data.
Extended Data Fig. 9 Characterisation of concentration-dependence of CLIP170 droplet formation (complement to Fig. 7).
a, Formation of GFP-CLIP170 droplets in lysates of HEK 293 cells at three different concentrations. Images shown are 10 min after the start of the experiment. Red lines indicate microtubules on which CLIP170 droplets were quantified (b; Fig. 7g,h). White rectangles indicate image sections shown in Fig. 7f. N = 3 independent TIRF assays from 2 sets of independent cell lysate preparation. b, Line scans of GFP-CLIP170 intensity profiles. Numbers indicate the identity of the scanned microtubule in (a). Note that the intensity profiles were only used to determine local maxima, from which distances between maxima were measured and plotted in Fig. 7h. The overall fluorescence intensity of the profiles was thus not considered for calculating droplet spacing. Numerical data are available in source data.
Extended Data Fig. 10 Characterisation of CLIP170 droplet behaviour in the presence of 1,6-hexanediol (complement to Fig. 7; Supplementary Video 19).
a, Formation of GFP-CLIP170 droplets (white) in lysates with polymerising microtubules. GMPCPP seeds are shown in green. N = 2 independent TIRF assays from 2 sets of independent cell lysate preparation. b, Development of GFP-CLIP170 droplets formed in (a) after the addition of 5% and 10% 1,6-hexanediol (w/v). Note that droplets do not dissolve at any of the tested conditions. BRB80 buffer was used as a control. N = 2 independent TIRF assays from 2 sets of independent cell lysate preparation. Numerical data are available in source data.
Supplementary information
Supplementary Information
The supplementary information pdf file contains legends, Supplementary Figs. 1, 2, 3, and references for all supplementary material including tables (which are provided as Excel files).
Supplementary Video 1
Spastin and EB3 behaviour in cell lysates (corresponding to Fig. 1b,c). a, Spastin–GFP from cell lysates severs taxol-stabilized microtubules (green). See still images in Fig. 1b. b, EB3–GFP (white) from cell lysates tracks growing microtubule ends. GMPCPP seeds are shown in green. Note the enrichment of EB3–GFP at a growing microtubule tip. Still images are shown in Fig. 1c.
Supplementary Video 2
Characterization of MAP candidates with growing microtubules in cell lysates (corresponding to Fig. 2c, Extended Data Fig. 3a and Supplementary Fig. 2a). Untransfected control lysates (a), GFP-tagged ATIP3 (b), CCDC66 (c) and CFAP (d) in lysates with growing microtubules. GFP-tagged MAPs are shown in white, GMPCPP seeds are in green. In the upper row, actin can polymerize (visualized by actin staining shown in Extended Data Fig. 3a for a, Supplementary Fig. 2a), while in the lower row, actin polymerization in the lysates was prevented by the addition of 11 µM of latrunculin A. Still images of all videos are shown in Extended Data Fig. 3a and Supplementary Fig. 2a.
Supplementary Video 3
Characterization of MAP candidates with growing microtubules in cell lysates (corresponding to Fig. 2c, Extended Data Fig. 3b, Supplementary Fig. 2b). GFP-tagged Cingulin (a), CKAP2 (b), CKAP2L (c) and CSAP (d) in lysates with growing microtubules. GFP-tagged MAPs are shown in white, GMPCPP seeds are in green. In the upper row, actin can polymerize (visualized by actin staining shown in Extended Data Fig. 3b for d, Supplementary Fig. 2b), while in the lower row, actin polymerization in the lysates was prevented by the addition of 11 µM of latrunculin A. Still images of all videos are shown in Extended Data Fig. 3b and Supplementary Fig. 2b.
Supplementary Video 4
Characterization of MAP candidates with growing microtubules in cell lysates (corresponding to Fig. 2b,c, Supplementary Fig. 2c). GFP-tagged DCLK1_4 (a), DCLK1_5 (b), DCX (c) and DCX_L (d) in lysates with growing microtubules. GFP-tagged MAPs are shown in white, GMPCPP seeds are in green. In the upper row, actin can polymerize (visualized by actin staining shown in Fig. 2b for c, Supplementary Fig. 2c), while in the lower row, actin polymerization in the lysates was prevented by the addition of 11 µM of latrunculin A. Still images of all videos are shown in Fig. 2b and Supplementary Fig. 2c.
Supplementary Video 5
Characterization of MAP candidates with growing microtubules in cell lysates (corresponding to Fig. 2c, Extended Data Fig. 4, Supplementary Fig. 2d). GFP-tagged EML1 (a), EML2 (b), EML3 (c) and EML4 (d) in lysates with growing microtubules. GFP-tagged MAPs are shown in white, GMPCPP seeds are in green. In the upper row, actin can polymerize (visualized by actin staining shown in Extended Data Fig. 4, Supplementary Fig. 2d), while in the lower row, actin polymerisation in the lysates was prevented by the addition of 11 µM of latrunculin A. Still images of all videos are shown in Extended Data Fig. 4 and Supplementary Fig. 2d.
Supplementary Video 6
Characterization of MAP candidates with growing microtubules in cell lysates (corresponding to Fig. 2b,c, Supplementary Fig. 2e). GFP-tagged GLFND1 (a), GLFND2 (b), HICE1 (c) and JPL1 (d) in lysates with growing microtubules. GFP-tagged MAPs are shown in white, GMPCPP seeds are in green. In the upper row, actin can polymerize (visualized by actin staining shown in Fig. 2b for d, Supplementary Fig. 2e), while in the lower row, actin polymerization in the lysates was prevented by the addition of 11 µM of latrunculin A. Still images of all videos are shown in Fig. 2b and Supplementary Fig. 2e.
Supplementary Video 7
Characterization of MAP candidates with growing microtubules in cell lysates (corresponding to Fig. 2b,c, Extended Data Figs. 3c,d,6a, Supplementary Fig. 2f). GFP-tagged JPL2 (a), MACF1(C1023) (b), MACF2(C1079) (c) and MAP2C (d) in lysates with growing microtubules. GFP-tagged MAPs are shown in white, GMPCPP seeds are in green. In the upper row, actin can polymerize (visualized by actin staining shown in Fig. 2b for b, Extended Data Fig. 3c,d for b,c, Extended Data Fig. 6a for d, Supplementary Fig. 2f), while in the lower row, actin polymerization in the lysates was prevented by the addition of 11 µM of latrunculin A. Still images of all videos are shown in Fig. 2b, Extended Data Figs. 3c,d,6a and Supplementary Fig. 2f.
Supplementary Video 8
Characterization of MAP candidates with growing microtubules in cell lysates (corresponding to Fig. 2c, Extended Data Fig. 6b, Supplementary Fig. 2g). GFP-tagged MAP2D (a), MAP4_X16 (b), MAP4_X20 (c) and MAP6 (d) in lysates with growing microtubules. GFP-tagged MAPs are shown in white, GMPCPP seeds are in green. In the upper row, actin can polymerize (visualized by actin staining shown in Extended Data Fig. 6b for a, Supplementary Fig. 2g), while in the lower row, actin polymerization in the lysates was prevented by the addition of 11 µM of latrunculin A. Still images of all videos are shown in Extended Data Fig. 6b and Supplementary Fig. 2g.
Supplementary Video 9
Characterization of MAP candidates with growing microtubules in cell lysates (corresponding to Fig. 2c, Extended Data Fig. 5, Supplementary Fig. 2h). GFP-tagged MAP7 (a), MAP7D1 (b), MAP7D2 (c) and MAP7D3 (d) in lysates with growing microtubules. GFP-tagged MAPs are shown in white, GMPCPP seeds are in green. In the upper row, actin can polymerize (visualized by actin staining shown in Extended Data Fig. 5, Supplementary Fig. 2h), while in the lower row, actin polymerization in the lysates was prevented by the addition of 11 µM of latrunculin A. Still images of all videos are shown in Extended Data Fig. 5 and Supplementary Fig. 2h.
Supplementary Video 10
Characterization of MAP candidates with growing microtubules in cell lysates (corresponding to Fig. 2c, Supplementary Fig. 2i). GFP-tagged MAP8 (a), MAP9 (b), MAP10 (c) and MAP11 (d) in lysates with growing microtubules. GFP-tagged MAPs are shown in white, GMPCPP seeds are in green. In the upper row, actin can polymerize (visualized by actin staining shown Supplementary Fig. 2i), while in the lower row, actin polymerization in the lysates was prevented by the addition of 11 µM of latrunculin A. Still images of all videos are shown in Supplementary Fig. 2i.
Supplementary Video 11
Characterization of MAP candidates with growing microtubules in cell lysates (corresponding to Fig. 2c, Supplementary Fig. 2j). GFP-tagged Parkin (a), PRC1 (b), SAXO1 (c) and SPEF1 (d) in lysates with growing microtubules. GFP-tagged MAPs are shown in white, GMPCPP seeds are in green. In the upper row, actin can polymerize (visualized by actin staining shown Supplementary Fig. 2j), while in the lower row, actin polymerization in the lysates was prevented by the addition of 11 µM of latrunculin A. Still images of all videos are shown in Supplementary Fig. 2j.
Supplementary Video 12
Characterization of MAP candidates with growing microtubules in cell lysates (corresponding to Fig. 2c, Extended Data Fig. 6c,d, Supplementary Fig. 2k). GFP-tagged SNPH_A (a), SNPH_C (b), Tau(0N-3R) (c) and Tau(0N-4R) (d) in lysates with growing microtubules. GFP-tagged MAPs are shown in white, GMPCPP seeds are in green. In the upper row, actin can polymerize (visualized by actin staining shown in Extended Data Fig. 6c,d for c,d, Supplementary Fig. 2k), while in the lower row, actin polymerization in the lysates was prevented by the addition of 11 µM of latrunculin A. Still images of all videos are shown in Extended Data Fig. 6c,d and Supplementary Fig. 2k.
Supplementary Video 13
Characterization of MAP candidates with growing microtubules in cell lysates (corresponding to Fig. 2c, Supplementary Fig. 2l). GFP-tagged TRAK1 (a) and TRAK2 (b) in lysates with growing microtubules. GFP-tagged MAPs are shown in white, GMPCPP seeds are in green. In the upper row, actin can polymerize (visualized by actin staining shown Supplementary Fig. 2l), while in the lower row, actin polymerization in the lysates was prevented by the addition of 11 µM of latrunculin A. Still images of all videos are shown in Supplementary Fig. 2l.
Supplementary Video 14
Unique activities of MAPs on growing microtubules (corresponding to Fig. 3a). Representative videos of selected MAPs inducing unique microtubule behaviour in lysates. MAPs are false-colour-coded. MAP7 (cyan) generated microtubule asters. CSAP (blue) induced formation of microtubule coils. MACF1(C1023) (green) formed hooks at growing microtubule ends. MAP2C (red) induced the formation of temporary hooks along microtubules and at growing microtubule ends, which further accumulated MAP2C to form droplet-like clusters. Still images of all videos are shown in Fig. 3a.
Supplementary Video 15
The impact of MAP–GFP concentration on microtubule behaviour in lysates (corresponding to Fig. 4b). The impact of MACF1(C1023)–GFP concentrations on microtubule hook formation was determined in lysates with four defined concentrations of this MAP. TIRF videos of MACF1(C1023)–GFP (GFP shown in inverted greyscale) show that hook-formation propensity decreases with decreasing MACF1(C1023)–GFP concentrations. Still images of all videos are shown in Fig. 4b.
Supplementary Video 16
The impact of a disease-related mutation of EML1 on microtubule binding (corresponding to Fig. 5, Extended Data Fig. 8). a, Microtubules polymerizing in a 1:1 mixture of lysates from HEK 293 cells expressing wild-type EML1 and EML1(T243A), respectively. microtubule seeds are visualized in red together with EML1(T243A)–mCherry, and wild-type EML1–GFP in green. b, Microtubules polymerising in a 1:1 mixture of lysates from HEK 293 cells expressing wild-type EML1–mCherry and EML1(T243A)–GFP, respectively. Note that the behaviour of wild-type and mutated EML1 is similar to the observations in a despite the inversion of the fluorescence tags. Still images of all videos are shown in Fig. 5b and Extended Data Fig. 8.
Supplementary Video 17
Helical reconstructions of EML1–GFP and EML4(N207) bound to microtubules (corresponding to Fig. 6c). Animated views of a symmetrized helical reconstruction (resolution 3.7 Å, low-pass filtered to 15 Å) of 14-protofilament microtubules (grey) with extra densities corresponding to EML1–GFP (green). Comparison with a similar helical reconstruction (EMDB 0331; resolution 3.6 Å, low-pass filtered to 15 Å) obtained for 13-protofilament microtubules (polymerized from brain tubulin) with purified EML4(N207) (red; Adib et al., 2019). Note that both MAPs bind along the microtubule protofilament ridge. Still images of all videos are shown in Fig. 6c.
Supplementary Video 18
Droplet formation by CLIP170 (corresponding to Fig. 7,8). a, A video showing the accumulation of overexpressed GFP–CLIP170 in a U-2 OS cell. The cell contours are visualized by bright-field microscopy. Note that initially small droplets are formed, which are later fusing. Note also the constant deformation of the GFP patches. Still images of this video are shown in Fig. 7a. b, Time-lapse of a TIRF assay with lysate of HEK 293 cells expressing GFP–CLIP170 (white). GFP–CLIP170 is forming regularly spaced droplets along the microtubules. The evolution of these droplets along one microtubule (orange line) is plotted as profiles of relative GFP intensity. Still images of these videos are shown in Fig. 7c. c, Microtubules grown in lysates of HeLa Kyoto cells stably expressing mCherry-α-tubulin (green), and transfected with GFP–CLIP170 (white). This video was recorded after GFP–CLIP170 droplets had formed and the new cell lysate with only mCherry-α-tubulin was added. Still images of this video are shown in Fig. 8c. d, At the end of the time-lapse imaging (c), microtubules were stained with the antibody YL1/2 for better visualization. Note that microtubules have grown almost exclusively from GFP–CLIP170 droplets (image is also shown in Fig. 8d).
Supplementary Video 19
Characterization of CLIP170 droplet behaviour in the presence of 1,6-hexanediol (complement to Extended Data Fig. 10). a, Formation of GFP–CLIP170 droplets (white) in lysates with polymerising microtubules. GMPCPP seeds are shown in green. b, Development of GFP–CLIP170 droplets formed in a after the addition of 5% and 10% 1,6-hexanediol (w/v). Note that droplets do not dissolve at any of the tested conditions. BRB80 buffer was used as a control.
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Original Coomassie brilliant blue stained gel used for Fig. 4a with visible molecular weight markers and full-size immunoblot as in Fig. 4a. An additional immunoblot with visible light shows molecular weight markers (red boxes show the sections of the gels or blots shown in the main figure).
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Jijumon, A.S., Bodakuntla, S., Genova, M. et al. Lysate-based pipeline to characterize microtubule-associated proteins uncovers unique microtubule behaviours. Nat Cell Biol 24, 253–267 (2022). https://doi.org/10.1038/s41556-021-00825-4
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DOI: https://doi.org/10.1038/s41556-021-00825-4
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