Download Integrating and Controlling Signals

Integrating and
Controlling
Signals
By Kimmie Bui
Cells change in response to
signals during and after
development

In many circumstances, responses depends on the
ability to receive cells to integrate multiple signals
and to control the availability of active cells.
 Competence Depends on Properties of Cells that
enable them to respond to Inductive Signals enable
them to respond to Inductive Signals.
 Competence- is the ability to respond to various
inductive signals.
 The reception of one signal may make cells
competent to receive another.
Ex: After one part of the liver is damaged
or surgically removed, increased amounts
of two signals, tumor necrosis factor
(TNF) and interleukin-6 (IL-6) are
produced as part of the response to liver
damage. These two signals cause
hepatocyte, which will increase their
production of transcription factors (NF-kB,
Stat3, API and CEBP) but does not
provide.
Liver
regeneration is important after it has
been damaged or poisoned. The unregulated
growth could lead to cancer.
Some signals can Induce
Diverse Cellular Response

Several mechanisms for producing diverse cellular
response to a particular signaling molecule seem
possible in principle.
 The strength or duration of the signal governs the
nature of the responses
 The pathway downstream of the receptor is not
really the same in different cell type.
 Converging inputs from other pathways modify
the response to the signal.
Limb Development Depends
on the Integration of Multiple
Extracellular Signal Gradients
Vertebrate limbs grow from small “buds”
composed of an inner mass of mesoderm cells
surrounded by a sheath of ectoderm.
 There are three dimensions to a limb.
-Anterior/posterior (thumb to little finger).
-Dorsal/ventral (palm verses back of hand).
-Proximal/distal (shoulder to fingers).

Fibroblast Growth Factor
(FGF10) - signal comes from
the mesoderm in specific
regions of the embryo flank

FGF10- is a local region of surface
ectoderm that becomes the signaling center.
 Apical Ectodermal Ridge (AER)- is at the
tip of emerging limb bud.
 Both of these drive persistent division of
mesoderm cells and continue limb growth.
Signals are buffered by the
Intracellular and Extracellular
Antagonist

Many organisms experience a wide variation in
their environment and must adapt or die.
 Inducible Antagonist-signal induces the
transcription of genes in the receiving cells.
 Anatogonist Not Induced by signal secreted
antagonist comes from the opposite direction; it
will block the action of the signal even in cells
receiving above-threshold amounts.
Conclusion:

In liver regeneration, early signals change cells
into a primed state in which they are competent to
respond to subsequent signals that causes growth
and mitosis.
 At least one signaling protein acts along each axis
of the developing limb bud. Cells responds to
many combination of signals, and the signals
reinforce the production of other signals to
coordinate growth and patterning in threedimension.
-Include intracellular and secreted proteins whose
production is induced by a particular signal. The
antagonist protein then feeds back; opposing the
ongoing action of the signal. Inducible antagonist
provides buffering in most signaling pathways to
compensate for excess or inadequate signals.
-Signals can also be controlled by antagonist that
are not induced by the signal itself. By binding to
signals, these antagonists prevent the signals from
binding to their specific receptors and activating
them.
Questions?