BIOL 370 – Developmental Biology
Topic #3
The Roles of Cell to Cell
Communication in Development
Lange
Morphogenesis is one of the major outstanding problems in the
biological sciences. It concerns the fundamental question of how
biological form and structure are generated.
Morphogenesis encompasses a broad scope of biological processes.
It concerns adult as well as embryonic tissues, and includes an
understanding of the maintenance, degeneration, and regeneration of
tissues and organs as well as their formation.
Reaggregation of cells from amphibian neurulae
A study that illustrates that even in this early stage, the presumptive
cells have already differentiated in ways that allows them to segregate
following experimental disaggregation.
Sorting out and reconstruction of spatial relationships in aggregates of embryonic amphibian cells
In this classic study by Townes and Holtfreter (1955), it is shown that a
variety of different disaggregated cells lines will display enough
differentiation to segregate into separate structural cell groupings.
Aggregates formed by mixing 7-day chick embryo neural retina cells with pigmented retina cells
This experimental mixture shows how the
segregation can visibly begin to be seen
after even just 5 hours (B) and is very
obvious and clear after 19 hours (C).
In physics, the dyne is a unit of force. One dyne is equal to 10 µN
(micronewtons). Equivalently, the dyne is defined as "the force required to
accelerate a mass of one gram at a rate of one centimetre per second squared.
In developmental biology, “dynes per centimeter” are units traditionally used to
measure surface tension.
For example, the surface tension of distilled water is 72 dyn/cm at 25 °C (77 °F).
Water displays cohesion (surface tension), but this cohesion varies based
upon other physical factors such as solute concentrations and temperature.
Hierarchy of cell sorting in order of decreasing surface tensions
In this segregation series,
cells that aggregate more
towards the interior have a
greater surface tension
score (dyne/cm) than do
the cells in the outer later.
These differences in
surface tension suggest
one mechanism by which
differentiation may
proceed.
Cell junctions can impact adhesion relationships between tissues as well. For
developmental effects, cadherins can play an especially crucial role.
Plasma membranes
of adjacent cells
Microvilli
Intercellular
space
Basement membrane
Intercellular
space
Plaque
Interlocking
junctional
proteins
Intercellular
space
Intercellular
space
Channel
between cells
(connexon)
Linker
Intermediate
glycoproteins
filament
(cadherins)
(keratin)
(a) Tight junctions: Impermeable
(b) Desmosomes: Anchoring
(c) Gap junctions: Communicating
junctions prevent molecules
junctions bind adjacent cells
junctions allow ions and small
from passing through the
together and help form an
molecules to pass from one cell
intercellular space.
internal tension-reducing
to the next for intercellular
network of fibers.
communication.
Cadherin-mediated cell adhesion
Importance of the amount of cadherin for correct morphogenesis
Importance of the amount of cadherin for correct morphogenesis (Part 1)
Importance of the amount of cadherin for correct morphogenesis (Part 2)
Importance of the types of cadherin for correct morphogenesis
Importance of the types of cadherin for correct morphogenesis (Part 1)
Importance of the types of cadherin for correct morphogenesis (Part 2)
Ventral furrow formation during Drosophila gastrulation internalizes the cells that will become the
mesoderm
Getting mesodermal cells inside the embryo during Drosophila gastrulation by regulation of the
cytoskeleton
Tracheal development in Drosophila
Schematic diagram of induction of the mouse lens (Part 1)
Schematic diagram of induction of the mouse lens (Part 2)
Schematic diagram of induction of the mouse lens (Part 3)
Genetic specificity of induction in amphibians
Sonic Hedgehog is one of three proteins in the mammalian
signaling pathway family called hedgehog. It plays a key
role in regulating vertebrate organogenesis, such as in the
growth of digits on limbs and organization of the brain and
neural pathways.
Hedgehog signal transduction pathway
Hedgehog signal transduction pathway (Part 1)
Hedgehog signal transduction pathway (Part 2)
(A) Sonic hedgehog expression is shown by in situ hybridization in the nervous system, gut, and
limb bud of a chick embryo. (B) Head of a cyclopic lamb
Apoptosis pathways in nematodes and mammals
Apoptosis – programed cell death that is needed for many
types of organ development. The mammalian brain is an
especially well known instance of widespread apoptosis.
Disruption of normal brain development by blocking apoptosis
C. elegans vulval precursor cells and their descendants (Part 1)
C. elegans vulval precursor cells and their descendants (Part 2)
Model for the generation of two cell types from two equivalent cells in C. elegans
Extracellular matrices in the developing embryo
Role of the extracellular matrix in cell differentiation
Basement membrane-directed gene expression in mammary gland tissue
Basement membrane-directed gene expression in mammary gland tissue (Part 1)
Basement membrane-directed gene expression in mammary gland tissue (Part 2)
End.