Immediate early gene
<p>Oct 29, 2009 9:32 PM
 
(from the NIH monograph which is 200 pages long ... takes 1-2 mins to download)
 
Brent Cochran first paper  Reulation of Immed Early Gene Expressions
 
IEGS are expressed inneurons in response to a variety of enurotropic stim.
Its been sugges. that long-termc changes in CNS behavior REQUIRE changes in gene expression.
Since IEG expression is co coupled to neuro activ and neurotrans relaease, it may now be possible to provide resolution
at single-cell level to correlate whte physio state of a neuron with behav and physio outputs.
 
IEG  are sometimes called early-resonse or primary response genes  ...
first identified not in nerv system but rather in stud. of cell growth regul.  in the 80s.
Polypeptide growth factors were found to be key modulators of cell growth and different.
 
Genes are induced with 1 hour of growth facotr treatment and are rgul at the level of transcription.
They are induced by polypeptide growth factors that bind to cell surface recptors in the absence of
ne protein synthesis.   That is,  induction of these genes is a primary reponse to events
at the cell surfraace and not secondary to toher waves of gene expres.
 
So, the FIRST WAVE does not require any protein synthesis ...  that is the disting factor of IEG
immed. early genes  ... they are formed by translation without any protein synthesis.
Some IEGs are the cell homologs of var retroviral oncogenes like c-myc, c-fos, c-jun.
 
Typical early-response gene is induced as early as within 5 mins of stim.  mRNA for c-fos is unstable and
persists for less than 2 hours.
 
The c-fos proto-oncogene is the best characgterized of the early-response gene at the level of transcription.
 
FUNCTION OF IEGS in CNS
 
One role that has been suggested for these genes is that <b>they mediate between
short-term signaling and long-term changes in the nervous system</b> (Morgan
and Curran 1989). This is especially intriguing, since <b>many studies have
implicated cAMP in the formation of long-term memory through transcriptional
changes in the nervous system (Goelet et al. 1986), tiowever, as the induction
of IEGs is transient, it is not yet clear how these genes would mediate such
long-term changes. They could be regulating the expression of structural
genes that could contribute to the formation of synapses and other structural
changes within neurons. Alternatively, early-response genes could serve as
a reset mechanism that functions to replenish and restore supplies of
neurotransmitters that h</b>ave been utilized. Another possible role for early-
response genes would be to modulate in the intermediate term the temporal
patterns of spike trains of given neurons. Since these genes are expressed
on a time scale of hours, they could contribute to short-term adaptive changes
in the activity of a given neuron. Obtaining the answers to questions like these
should be the focus of future research.
 
 
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