C
Cncabej
Guest
Mon, 8 March 2004 004:12 Peter F. wrote:
"CNCabej" <[email protected]> wrote
> I would rather say that there is one integrated control
> system, with the
CNS as
> its controller that is limited by genes (G), as well by
> numerous external
and
> internal stimuli.
>I think that what you are expounding fits in somewhere at
>the center of the most interesting and fascinating of all
>fields of scientific inquiry.
>(It makes me salivate without being able to chew and
>swallow - but I still love it from a distance.
<
If this is really so (and I believe it is), is it not
paradoxical that people here in sbe are showing so little
interest for "the most interesting and fascinating of all
fields of scientific inquiry"? I wonder whether you have an
explantion.
>However, even if the notion and embryonic theory of "the
>histone code" might currently not catalyze conceptual
>clarity or inspire further insight, I still think it is
>generally so relevant to what is discussed here that you
>ought to have at least given it a mention.
>If only for sake of a good (comprehensively spread-
>out) measure.
"The histone code", if you mean the remodelling of the
chromatin by acetylation/deacetylation of histones, is an
essential part of the integrated control system, but it was
not mentioned here because of lack of space. In principle,
the expression of all housekeeping genes is related to that
remodelling.
The integrated (epigenetic) system of control is a
hierarchic system where the chromatine represents a
downstream element in the system. In a very simplified
scheme upstream the chromatine are signal transduction pathways<----
membrane receptors <---- their respective extracellular
signals (protein hormones, growth factors, secreted
proteins, neurotransmitters etc.)<--- hormones of the target
endocrine glands<--- pituitary stimulating hormones <---
hypothalamic releasing hormones <---- brain chemical signals
<---processing of the internal/external stimuli. Downstream
the chromatine ("the histone code") are transcription
factors and genes.
The epigenetic system of control, with the CNS as its
controller, controls the function of all housekeeping genes,
genes whose differential expression determines the type of
the cell (even the so-called cell-cell interactions are
interactions at the level of downstream elements of signal
cascades ultimately originating in the CNS).
The function of the integrated system of control, with the
CNS as its controller, is to maintain the inexorably eroding
metazoan structure at all the different levels of
organization. This implies that the system
1)is in possession of information on the "normal"
physiological and morphological state.
2) does monitor the state of the system (based on the
pervasive presence of the neural tissue thoughout the
animal body).
3) processes the input and by comparing with the set points
it establishes detects deviations from the norm.
4) sends messages (in the form of signal cascades) to
affected parts for restoring the normal state.
Being in possession of information for the normal structure
the integrated system is at the same time the epigenetic
system of heredity as it is demonstrated by the fact that it
regulates and controls
5. The formation of the egg and sperm cells
6. The placement of maternal cytoplasmic factors in
the egg cell.
7. The early embryonic development (which is regulated not
by zygotic genes, but by maternal cytoplasmic factors)
up to the phylotypic stage, when a functioning CNS
first arises.
8.The postphylotypic development, including the post-natal
development (the
All the above suggest that the genetic system of heredity,
which is responsible for most of the hereditary characters
in unicellulars, in metazoans is subordinate to the
epigenetic system of heredity.
If this is really so, how can one determine whether the
evolution of genes is the cause or a consequence of
evolution? Mary Jane West-Eberhard in her recently published
book presents some curious arguments that genes in her
expression are "followers not leaders" in evolution. While
examples of inherited changes in morphology without changes
in genes are known, does any one know an example of how a
mutation in a gene brought about an advantageous
morphological change in metazoans? If not, with H.F. Nijhout
we all have to admit that genes do no more than producing
chemicals (RNA and proteins).
"CNCabej" <[email protected]> wrote
> I would rather say that there is one integrated control
> system, with the
CNS as
> its controller that is limited by genes (G), as well by
> numerous external
and
> internal stimuli.
>I think that what you are expounding fits in somewhere at
>the center of the most interesting and fascinating of all
>fields of scientific inquiry.
>(It makes me salivate without being able to chew and
>swallow - but I still love it from a distance.
<If this is really so (and I believe it is), is it not
paradoxical that people here in sbe are showing so little
interest for "the most interesting and fascinating of all
fields of scientific inquiry"? I wonder whether you have an
explantion.
>However, even if the notion and embryonic theory of "the
>histone code" might currently not catalyze conceptual
>clarity or inspire further insight, I still think it is
>generally so relevant to what is discussed here that you
>ought to have at least given it a mention.
>If only for sake of a good (comprehensively spread-
>out) measure.
"The histone code", if you mean the remodelling of the
chromatin by acetylation/deacetylation of histones, is an
essential part of the integrated control system, but it was
not mentioned here because of lack of space. In principle,
the expression of all housekeeping genes is related to that
remodelling.
The integrated (epigenetic) system of control is a
hierarchic system where the chromatine represents a
downstream element in the system. In a very simplified
scheme upstream the chromatine are signal transduction pathways<----
membrane receptors <---- their respective extracellular
signals (protein hormones, growth factors, secreted
proteins, neurotransmitters etc.)<--- hormones of the target
endocrine glands<--- pituitary stimulating hormones <---
hypothalamic releasing hormones <---- brain chemical signals
<---processing of the internal/external stimuli. Downstream
the chromatine ("the histone code") are transcription
factors and genes.
The epigenetic system of control, with the CNS as its
controller, controls the function of all housekeeping genes,
genes whose differential expression determines the type of
the cell (even the so-called cell-cell interactions are
interactions at the level of downstream elements of signal
cascades ultimately originating in the CNS).
The function of the integrated system of control, with the
CNS as its controller, is to maintain the inexorably eroding
metazoan structure at all the different levels of
organization. This implies that the system
1)is in possession of information on the "normal"
physiological and morphological state.
2) does monitor the state of the system (based on the
pervasive presence of the neural tissue thoughout the
animal body).
3) processes the input and by comparing with the set points
it establishes detects deviations from the norm.
4) sends messages (in the form of signal cascades) to
affected parts for restoring the normal state.
Being in possession of information for the normal structure
the integrated system is at the same time the epigenetic
system of heredity as it is demonstrated by the fact that it
regulates and controls
5. The formation of the egg and sperm cells
6. The placement of maternal cytoplasmic factors in
the egg cell.
7. The early embryonic development (which is regulated not
by zygotic genes, but by maternal cytoplasmic factors)
up to the phylotypic stage, when a functioning CNS
first arises.
8.The postphylotypic development, including the post-natal
development (the
All the above suggest that the genetic system of heredity,
which is responsible for most of the hereditary characters
in unicellulars, in metazoans is subordinate to the
epigenetic system of heredity.
If this is really so, how can one determine whether the
evolution of genes is the cause or a consequence of
evolution? Mary Jane West-Eberhard in her recently published
book presents some curious arguments that genes in her
expression are "followers not leaders" in evolution. While
examples of inherited changes in morphology without changes
in genes are known, does any one know an example of how a
mutation in a gene brought about an advantageous
morphological change in metazoans? If not, with H.F. Nijhout
we all have to admit that genes do no more than producing
chemicals (RNA and proteins).