UMMS Affiliation

Division of Cell Biology and Imaging, Department of Radiology; Witman Lab

Publication Date


Document Type



Cell Biology | Cells


Cilia are essential organelles required for cell signaling and motility. Nearly all motile cilia have a '9+2' axoneme composed of nine outer doublet microtubules plus two central microtubules; the central microtubules together with their projections are termed the central apparatus (CA). In Chlamydomonas reinhardtii, a model organism for studying cilia, 30 proteins are known CA components, and approximately 36 more are predicted to be CA proteins. Among the candidate CA proteins is the highly conserved FAP70 (CFAP70 in humans), which also has been reported to be associated with the doublet microtubules. Here, we determined by super-resolution structured illumination microscopy that FAP70 is located exclusively in the CA, and show by cryo-electron microscopy that its N-terminus is located at the base of the C2a projection of the CA. We also found that fap70-1 mutant axonemes lack most of the C2a projection. Mass spectrometry revealed that fap70-1 axonemes lack not only FAP70 but two other conserved candidate CA proteins, FAP65 (CFAP65 in humans) and FAP147 (MYCBPAP in humans). Finally, FAP65 and FAP147 co-immunoprecipitated with HA-tagged FAP70. Taken together, these data identify FAP70, FAP65 and FAP147 as the first defining components of the C2a projection.


ASH domains, Axonemal central apparatus, CFAP70, FAP147, FAP174, FAP65, Flagella, MYCBP, MYCBPAP

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Copyright © 2021. Published by The Company of Biologists Ltd. Publisher PDF posted with 12 month embargo as allowed by the publisher's self-archiving policy at

DOI of Published Version



Hou Y, Zhao L, Kubo T, Cheng X, McNeill N, Oda T, Witman GB. Chlamydomonas FAP70 is a component of the previously uncharacterized ciliary central apparatus projection C2a. J Cell Sci. 2021 Jun 15;134(12):jcs258540. doi: 10.1242/jcs.258540. Epub 2021 Jun 28. PMID: 33988244. Link to article on publisher's site

Journal/Book/Conference Title

Journal of cell science

Related Resources

Link to Article in PubMed

PubMed ID


Available for download on Tuesday, June 28, 2022