Cilia, centrioles andciliogenesis
MG 5607Shubhra Majumder
What are cilia or flagella?
Cilia are ‘hair-like’ projections fromcell surface
Primary cilia Centrosomes DNA
A. Why cilia are important?
B. How are they formed?B. How are they formed?
Bacterial flagella are not structurallysimilar to eukaryotic flagella
Figure 15-71a: MolecularBiology of the Cell
• Bacterial flagella help in motility and rotation
• A flagellum is made of Basal body, Hook andFilament
• Bacterial flagella are not microtubule-based
• The major component is Flagellin
Subtypes of cilia
Flagella inunicellulareukaryotes
Cilia
Non-motile ciliaMotile cilia
Motile cilia inmulticiliated cells
Sperm flagellum
Flagella provide motility
High speed video microscopy of a Chlamydomonas reinhardtiicell movement using newly developed “Cell LOcating withNanoscale Accuracy (CLONA)” video analysis method
(Fujita et al., Biophys J, 2014)
Ciliary beating regulates fluid flow
Video microscopy of mouse tracheal epithelial cells(Lechtreck K-F. et al., J Cell Biol. 2008)
Multiciliated cells are found in epithelia of respiratory tract,ependyma of brain ventricles etc.
Primary cilium as sensory organMost vertebrate cells contain primary cilia at some point, usually whenthey are differentiated (non-proliferating)
Primary cilia transduce chemical, mechanical or developmental signal
Extra-cellular sensory signaling: Primary cilia in Olfactory sensoryneurons, photoreceptor cells of retina
Mechanical sensor: Cilia in the epithelial cells of renal tubes sensefluid-flow
Intracellular signaling: Sonic Hedgehog signaling
A. Why cilia are important?
B. How they are formed?
Axoneme
Basal body
Plasma membrane
Transition zone
Ciliary membrane
Complex structure of a cilium
Ishikawa and Marshall, 2011Majumder and Fisk, Cell Cycle, 2013
Arl13B Acetylatedtubulin
Merge
Ciliarymembrane
Axoneme
A centrosome contains a pair ofcentrioles
Figure 16-31b: MolecularBiology of the Cell
Daughtercentriole
Mother centriole
Appendages
Figure 16-84b: MolecularBiology of the Cell
Triplet microtubules
(PCM)
Ultra-structure of centrioles
C. Rieder
Appendages
Mothercentriole
Daughtercentriole
Triplet Microtubules
M. Bornens
Figure 16-30a-b: MolecularBiology of the Cell
The centrosome is the majormicrotubule organizing center
Figure 16-31a: Molecular Biology of the Cell
γ-TuRC mediates microtubule nucleation
Reconstructed from EMof individual complexes
EM of a singlemicrotubulenucleatedfrom γ-TuRC
Figure 16-30c: MolecularBiology of the Cell
Reconstituted image of a centrosomefunctioning as MTOC
Centriole duplication cycle
Centrosomeseparation
Elongation andmaturation
Procentrioleformation
Centrioledisengagement
G1 S
G2M
MCDC
Centrosome separation afternew centrosome assembly
MicrotubulesCentrosomes
Human osteosarcoma U2OS cell
Shubhra Majumder
DNA
Centrosomes form the bipolarspindle
Microtubules Centrosomes
Mouse fibroblast NIH 3T3 cell
Harold FiskKinetochores
DNA
The cartwheel provides the baseto assemble a new centriole
Loncarek and Khodjacov, 2009
Cartwheel
Assembly ofcentriolar MTaround cartwheel
Elongation ofprocentriole Cartwheel
disappear aftercentriole maturation
The cartwheel provides thenine-fold symmetry
Gonczy, Nat Rev Mol Cell Biol. 2012
Electron micrograph of the proximalregion of a Chlamydomonas reinhardtiicentriole
A-C linker
A. Why cilia are important?
B. How are they formed?
Structural components of a cilium
Reiter et al. EMBO Rep. 2012
Structure of motile vs non-motile cilia
Reiter et al. EMBO Rep. 2012
Figure 16-81: MolecularBiology of the Cell
Arrangement of ciliary microtubules
A
B
Electron micrograph of the flagellum ofChlamydomonas reinhardtii
Dynein provides the ciliary motility
Figure 16-82: MolecularBiology of the Cell
Head
Stem
Base
Figure 16-83A: MolecularBiology of the Cell
Flagellar dynein produces sliding forceA B
Figure 16-83B: MolecularBiology of the Cell
Sliding force generates the bendingof axonemal microtubules
Figure 16-80: MolecularBiology of the Cell
Wave-like flagellary motion vs ciliary beating
Conservation of ciliary ultrastructure
Carvalho-Santos et al. J Cell Biol. 2011
The cartwheel provides the nine-foldsymmetry
Gonczy, Nat Rev Mol Cell Biol. 2012
Basal bodies are modified centrioles
Figure 16-84A: MolecularBiology of the Cell
Assembly of a cilium
Reiter et al. EMBO Rep. 2012
Golgi
Intraflagellar transport in cilia
Ishikawa and Marshall, 2011
IFT: A bi-directional movement of a largeprotein complex on microtubules
Motor activity of kinesin
Source: The lab website of Dr Ron Vale http://valelab.ucsf.edu/external/moviepages/moviesMolecMotors.html
Motor activity of cytoplasmic dynein
Carter, J Cell Sc. 2013
Walking of cytoplasmic dynein motor onmicrotubules
Intraflagellar transport in cilia
Total Internal Reflection Fluorescence (TIRF) microscopy of IFT20-GFPin Chlamydomonas flagellumEngel et al., Methods Cell Biol. 2009
Ciliary disassembly is coordinated with cellcycle to maintain centriole homeostasis
G0Primary cilia assembly
Disassembly
G1 S
G2M
MCDC
BB
Regulation of ciliary disassembly
Active mechanisms:
1. HDAC6 mediated deacetylation of axonemal microtubules
2. Depolymerization of the axonemal microtubules by kinesins
Pugacheva et al., Cell, 2007
Ciliopathies or cilia-related diseases
Motile cilia
Respiratory tract infection
Male infertility
Kartagener’s syndrome
Situs inversus (loss of left-right asymmetry)
Primary cilia
Polycystic kidney disease
Retinal dystrophy
Developmental defects in organs
Cancer