Cilia, centrioles and
ciliogenesis
MG 5607
Shubhra Majumder
What are cilia or flagella?
Cilia are ‘hair-like’ projections from
cell surface
Primary cilia Centrosomes DNA
A. Why cilia are important?
B. How are they formed?
Bacterial flagella are not structurally
similar to eukaryotic flagella
• Bacterial flagella help in motility and rotation
• A flagellum is made of Basal body, Hook and
Filament
• Bacterial flagella are not microtubule-based
• The major component is Flagellin
Figure 15-71a: Molecular
Biology of the Cell
Subtypes of cilia
Cilia
Motile cilia
Flagella in
unicellular
eukaryotes
Sperm flagellum
Non-motile cilia
Motile cilia in
multiciliated cells
Flagella provide motility
High speed video microscopy of a Chlamydomonas reinhardtii
cell movement using newly developed “Cell LOcating with
Nanoscale 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 organ
Most vertebrate cells contain primary cilia at some point, usually when
they are differentiated (non-proliferating)
Primary cilia transduce chemical, mechanical or developmental signal
Extra-cellular sensory signaling: Primary cilia in Olfactory sensory
neurons, photoreceptor cells of retina
Mechanical sensor: Cilia in the epithelial cells of renal tubes sense
fluid-flow
Intracellular signaling: Sonic Hedgehog signaling
A. Why cilia are important?
B. How they are formed?
Complex structure of a cilium
Ciliary membrane
Axoneme
Arl13B
Plasma membrane
Acetylated Merge
tubulin
Axoneme
Ciliary
membrane
Transition zone
Majumder and Fisk, Cell Cycle, 2013
Basal body
Ishikawa and Marshall, 2011
A centrosome contains a pair of
centrioles
(PCM)
Daughter
centriole
Mother centriole
Appendages
Triplet microtubules
Figure 16-84b: Molecular
Biology of the Cell
Figure 16-31b: Molecular
Biology of the Cell
Ultra-structure of centrioles
Triplet Microtubules
Appendages
Mother
centriole
C. Rieder
Daughter
centriole
M. Bornens
The centrosome is the major
microtubule organizing center
Figure 16-30a-b: Molecular
Biology of the Cell
γ-TuRC mediates microtubule nucleation
Reconstructed from EM
of individual complexes
Figure 16-31a: Molecular Biology of the Cell
EM of a single
microtubule
nucleated
from γ-TuRC
Reconstituted image of a centrosome
functioning as MTOC
Figure 16-30c: Molecular
Biology of the Cell
Centriole duplication cycle
Centriole
disengagement
MC
DC
G1
M
S
Procentriole
formation
G2
Elongation and
maturation
Centrosome
separation
Centrosome separation after
new centrosome assembly
Human osteosarcoma U2OS cell
DNA
Centrosomes
Microtubules
Shubhra Majumder
Centrosomes form the bipolar
spindle
Mouse fibroblast NIH 3T3 cell
DNA
Microtubules Kinetochores Centrosomes
Harold Fisk
The cartwheel provides the base
to assemble a new centriole
Cartwheel
Assembly of
centriolar MT
around cartwheel
Elongation of
procentriole
Cartwheel
disappear after
centriole maturation
Loncarek and Khodjacov, 2009
The cartwheel provides the
nine-fold symmetry
A-C linker
Electron micrograph of the proximal
region of a Chlamydomonas reinhardtii
centriole
Gonczy, Nat Rev Mol Cell Biol. 2012
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
Arrangement of ciliary microtubules
B
A
Electron micrograph of the flagellum of
Chlamydomonas reinhardtii
Figure 16-81: Molecular
Biology of the Cell
Dynein provides the ciliary motility
Head
Stem
Base
Figure 16-82: Molecular
Biology of the Cell
Flagellar dynein produces sliding force
A B
Figure 16-83A: Molecular
Biology of the Cell
Sliding force generates the bending
of axonemal microtubules
Figure 16-83B: Molecular
Biology of the Cell
Wave-like flagellary motion vs ciliary beating
Figure 16-80: Molecular
Biology of the Cell
Conservation of ciliary ultrastructure
Carvalho-Santos et al. J Cell Biol. 2011
The cartwheel provides the nine-fold
symmetry
Gonczy, Nat Rev Mol Cell Biol. 2012
Basal bodies are modified centrioles
Figure 16-84A: Molecular
Biology of the Cell
Assembly of a cilium
Golgi
Reiter et al. EMBO Rep. 2012
Intraflagellar transport in cilia
IFT: A bi-directional movement of a large
protein complex on microtubules
Ishikawa and Marshall, 2011
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
Walking of cytoplasmic dynein motor on
microtubules
Carter, J Cell Sc. 2013
Intraflagellar transport in cilia
Total Internal Reflection Fluorescence (TIRF) microscopy of IFT20-GFP
in Chlamydomonas flagellum
Engel et al., Methods Cell Biol. 2009
Ciliary disassembly is coordinated with cell
cycle to maintain centriole homeostasis
Disassembly
BB
MC
DC
Primary cilia assembly
G0
G1
M
S
G2
Regulation of ciliary disassembly
Pugacheva et al., Cell, 2007
Active mechanisms:
1. HDAC6 mediated deacetylation of axonemal microtubules
2. Depolymerization of the axonemal microtubules by kinesins
Ciliopathies or cilia-related diseases
Motile cilia
Primary cilia
Respiratory tract infection
Polycystic kidney disease
Male infertility
Retinal dystrophy
Kartagener’s syndrome
Developmental defects in organs
Situs inversus (loss of leftright asymmetry)
Cancer