DEV2011 Study Guide - Final Guide: Intermediate Filament, Cell Adhesion, Cell Adhesion Molecule
25 May 2018
School
Department
Course
Professor
Lecture 15 – Cytoskeleton and Cell Mobility in Development
Nature of Cytoskeleton
• Complex network of filaments extending throughout cytoplasm of cells
o Function:
▪ Stabilises and protects cell
▪ Maintenance of cell shape
▪ Cellular movement
• Cytoskeletal filaments (3)
1. Actin microfilaments
▪ Function: structural support, motility (cell migration)
2. Microtubules
▪ Function: cell division, mobility (intracellular transport of
molecules)
3. Intermediate filaments
▪ Function: support for nuclear membrane, cell adhesion,
structural and shape
Actin Microfilaments and Movement
• Actin are helical polymers of protein actin
(flexible)
• Dispersed throughout cell – highly concentrated
in cortex
o Beneath plasma membrane
o Most abundant protein within eukaryotic
cells
• Use electron microscopy
• Functions
o Provide cell shape via actin cortex
o Participate in cell attachment points
o Allow cell movement
o Cytokinesis (division of cells) dependent on actin
• Structure
o Formation of fibre much more active at plus end
o Plus and minus end
find more resources at oneclass.com
find more resources at oneclass.com
o Two intertwined chains of globular actin monomers: G actin and F
actin
• Migration
o Filopodium – movement in one direction
▪ Between filopodia: lamellipodia – formed of actin networks
o Excessary proteins help bind actin fibres into specific networks
Intermediate Filaments and Interaction with Plasma Membrane
• Rope like filaments – monomeric fibre (8-10nm)
• Extremely strong – don’t break down
• In epithelial cells – span cytoplasm from one cell-cell junction to another –
adhesion
• Built up of fibrous protein subunits
• Form cobweb like structure within cytoplasm
• Functions
o Provides mechanical strength (across tissues)
▪ Links with cell junction
o Anchor junction complexes
▪ Distribution of tissue tensile stress in epithelia by anchor
junctions through desmosomes (cell-cell junction) and
hemidesmosomes (cell matrix junction)
▪ Form flexible but resilient framework that gives structural
support to an epithelium
o Organelle organization
▪ Provides basic structure of such tough epithelial keratin
structures: features, hair, horn and nails
▪ Assembly of nuclear envelope
o Organise tissue layers
Microtubules
• Long, hollow cylinders made up of dimer of alpha and beta tubules (protein
tubulin) → form heterodimers
• More rigid than actin filaments
• Attached to microtubule – centrosome
• Found during interphase – separate cells
• Function
o Make up centrioles and form spindle in dividing cells
o Form flagella and cilia of cell
▪ 9+2 arrangement of microtubules:
• 9 fused pairs on outside of cylinder
• 2 unfused paris in centre
o Provide pathway for intracellular movement of organelles, vesicles and
proteins
o Significant role for axonal migration by guiding neuronal growth
• Assemble and disassemble depending on temperature and surrounding tubulin
concentration
• Microtubule treadmilling
o Polymerisation: addition of heterodimers at one end
o Depolymerisation: removal of heterodimers at other end
find more resources at oneclass.com
find more resources at oneclass.com
• Regulated by microtubule-associated proteins (MAPs)
o Some stabilise, some destabilise microtubules
Cell Migration
• Movement of cells underlies tissue formation during embryonic development
and wound healing and immune responses in adult
• Collective cell migration
o Essential in building,
shaping, remodelling
complex tissues and
compartments: epithelia,
ducts, glands, vessels
• Single cell migration
o Allows cells to cover local
distances and integrate into
tissues (e.g. neural crest cell
migration)
Lecture 16 – Developmental Origins of Muscle
Skeletal Muscle
• Origin: from paraxial mesoderm → somite →
myotome: divides into epimere (back muscles)
and hypomere (thorax, abdomen)
• Control: voluntary
• Develop from fusion of myoblasts → fuse to
form myofibres
• Long fibres, multinucleated fused cells, striated
• Neural tube can direct development into
skeletal muscle
• Very young somite → mesenchyme
• Myoblasts: undergo frequent divisions
o Coalesce with formation of a multinucleated, syncytial muscle fibre
(myotube)
o Nuclei at this stage centrally located in muscle fibre → nuclei
gradually displaced to periphery of cell
• Myoblasts fuse to form new skeletal muscle fibres: striated
o Develop into tubes with many nuclei
o Produce contractile filaments – accumulate in fused cytoplasms
▪ Results in very long muscle fibres with multiple nuclei
• Sarcomeres (contractile apparatus)
o Smallest contractile unit of skeletal muscle – give striations
o Rows of sarcomeres form myofibrils
• High nutritive requirements (capillary)
• Sequence of genes from neighbouring tissues that signal to somites to start
signalling events of myotome → form myoblasts → myofiber
• Genes important
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Lecture 15 cytoskeleton and cell mobility in development. Intermediate filaments and interaction with plasma membrane: rope like filaments monomeric fibre (8-10nm, extremely strong don"t break down. Intercalated discs form between adjacent cells: as heart increases in size with development disassemble their contractile filaments to undergo mitosis, single, centrally placed nucleus, striations and branching evident. Fibres: structure of collagen: collagen fibres most abundant, tough and flexible, resist stretching, e. g. Extracellular matrix (ecm: ecm usually made by cells within it, composition of matrix: according to function of tissue, gel like (due to hydration, very strong (fibres within it, rock hard (bone): mineralisation, fluid like (blood): dissolved proteins. Endochondral ossification: making cartilage into bone, occurs during later foetal development, bone tissue (long bones) is created from cartilage template, cartilage is not vascularised but bone is. Intracellular domain: binds to keratin intermediate filaments: antibodies produced against integrins blistering of epithelia.
