Re: Epigenetic Control of Development, Homeostasis and Reproduction

On Feb 2, 9:45 pm, CNCa...@xxxxxxx wrote:
On Feb 2, 2:05 pm, rnorman <rnor...@xxxxxxxxx> wrote:





On Jan 30, 11:52 pm, CNCa...@xxxxxxx wrote:

I am avoiding long and useless discussions on irrelevant interactions..
I will simply present a few of numerous examples of signals from
the brain that induce development of organs.

1. Pulses of ecdysone biosynthesis "direct the destruction of obsolete
 larval tissues and their replacement by tissues and structures that
form the adult fly...via the precise stage- and tissue-specific
regulation
 of key death effector genes. (Draizen et al., 1999). And, as it is
known,
these pulses ate just echo of pulses of the neuropeptide PTTH
(prothoracicotropic hormone) released by the brain.

2. Metamorphosis in molluscs, in cnidarians, in insects and in
amphibians.

3. Control of muscle fiber differentiation durin  myogenesis in
Drosophila
(Fernandes and Keshishian, 2005)Based on experimental evidence, it is
concluded that the motoneuron influences both the number of cells
available for fusion, as well as potentially regulates the fusion
events themselves. This in our view is an elegant mechanism for
controlling muscle fiber differentiation during myogenesis, and may
have evolved as a way to ensure that muscle primordia develop into
muscles that meet the diverse demands placed on them by the nervous
system. (Fernandes and Keshishian, 2005)

4. After formation of the neural tube and the CNS, the heart is the
first
embryonic organ to develop in most vertebrates studied. The neural
tube
sends signals (Wnt3 and Wnt8) that inhibit  induction of
cardiogenesis
and promote  blood cell differentiation of mesoderm cells along the
whole
of its length, except for the region where the heart nomally develops..
By simply using Wnt antagonists it has been possible to induce
ectopic
heart development (Schneider and Mercola, 2001; Tzahor and Lassar,
2001).

5. In the embryonic limb skin VEGFs  secreted by local nerves  induce
formation of
blood vessels, thus explaining the old anatomic observation on the
association of
nerves and blood vessels:
"Peripheral nerves provide a template that determines the organotypic
pattern of blood vessel branching and arterial differentiation in the
skin, via local secretion of VEGF." (Mukoyama et al., 2002).

For numerous examples of the neural control of development of organs
and organ
systems visit my website
nelsoncabej.com orhttp://www.epigeneticscomesofage.com

So, on item 1 above, I believe you have misinterpreted your citation.

Please, see above, who has misinterpreted and the examples I present
on
the neural control of organogenesis here and in my website.

On item 2 above, the circulatory system develops and is functional
before the CNS is well formed, certainly before it is truly
functional.

The example 5 shows the contrary:

"Peripheral nerves provide a template that determines the organotypic
pattern of blood vessel branching and arterial differentiation in the
skin, via local secretion of VEGF. (Mukoyama et al., 2002) (certainly,
honest mistake).

On items 3, 4, and 5 above, you present no evidence but simply make
rather sweeping statements.

In relation to 3, I have already presented examples of the evolution
of
the change in the size of M. sexta, evolution of caste polymorphism in
ants,
loss of teeth in birds, but you can further read on the role of
auditory mechanisms,
olfactory mechanisms, visual mechanisms, and electrosensory mechanisms
in
sympatric speciation in chapter 20 of my book Epigenetic Principles of
Evolution
or in my website

In relation to 4 (role of the nervous system in transgenerational
plasticity) look at the following example:

Under normal to favorable conditions in environment, Daphnia magna
reproduces
asexually by producing only diploid female offspring. It responds to
the stressful environemntal conditions (shortening of the photoperiod,
drop in food quality and quantity, crowding etc.) by activating the
neuroendocrine cascade CHH (crustacean
hyperglycemic neuropeptides --> hormone methyl farnesoate via the CNS
-->
X organ/sinus gland complex --> ovary. Thus the crustacean  transduces
the
unfavorable environmental stimuli into inherited phenotypic changes in
the offspring,
giving birth to both male and sexualy responsive female individuals,
leading to sexual reproduction and production of eggs that are
different from the parental eggs in
morphology (contain a protective cover ephippium), biochemistry
(contain substances
that protect them from drying and freezing), and in the life history
(can delay hatching for many yearsuntil favorable conditions in the
environment return) (Rider et al. 2005).

I hope to have  been helpful.

As usual we are speaking at cross purposes.  It is very true that the
nervous system is involved in the tissue interactions involved in
early development.  That does not mean that the nervous system  ***as
an information processing system*** is involved.  It only means that
the nervous cells interact with their neighbors in the same way that
epithelial cells interact with their neighbors.  

This is not correct. It is not about any interactions. It is about
signal cascades regulating these processes during the development,
in cases of developmental plasticity, transgenerational developmental
plasticity and evolution. And signal cascades are unmistakable
indicators of the direction of the flow of information. The
information
in all these cases flows from the nervous system to the target
organs.
This is epigenetic information (it comes not from DNA and flows not
from DNA to RNAs to proteins.

The information processing capability of the nervous system is not involved, for
example, in the fact that blood vessels tend to parallel peripheral
nerve pathways.  Since nerve and muscle necessarily function together
as a neuromuscular unit of action, it is no surprise that nerve and
muscle influence each other in development.  

The example of the sensory neurons that by secreting VEGFdetermine
cell differentiation and patterning of arteries in their vicinity is a
typical
case the of a structure on the template of a nerve. Let me quote once
again the investigator:

"Peripheral nerves provide a template that determines the organotypic
 pattern of blood vessel branching and arterial differentiation in the
 skin, via local secretion of VEGF. "(Mukoyama et al., 2002)

There is no interaction between nerves and blood vessels in this case
(in fact initially there areno blood vessels to interact).
The nerve secretes along its whole length secretes VEGF which induces
adjacent formation of blood vessels, thus serving as a template for
blood vessel formation. I believe we both agree that a template
provides information for formation of its copy rather than interacts
with the unexisting copy (remember  DNA that serves
as a template for RNA synthesis).

The formation of the blood vessel is not a random
process (no random process could repeatedly produce the same pattern
as it occurs with blood cells) but a process  for which the nerve
invests
epigenetic information.

And it is very clear that
in an already well developed animal life stage, the nervous system is
part of the regulatory machinery triggering events like metamorphosis.

I doubt whether this general statement can argue anything.

None of this is related to epigenetics, though, unless you stretch the
notion of epigenetics to include any cellular function apart from the
molecular biology of DNA.  Cells are motile, cells secrete, cells are
irritable (in the technical sense of responding electrically to
stimuli), cells are biochemical factories, cells transport material
across membranes;  all these things are separate from genetics.  None
of this is called epigenetics; it is called "cell physiology".

This is a clear a (honest) distraction. It is irrelevant to our topic
of signals from
the brain that induce development of organs.

Nothing you have said and none of the citations you provide are in any
way connected to the notion that epigenetic information is transmitted
from parent to offspring and is involved with evolution in any way.

This is another distraction. My intention in this post is to provide
you
a few of numerous examples of signals from the brain that induce
development of organs. I would  like to see you to consider whether my
examples
prove my idea on the role of the central nervous system in the
development
rather than see irrelevant general statements.

I have already acknowledged that there are interactions between (i.e.
"signals from") the nervous system and other tissues that influence
development. What you have never shown is that this has anthing in
the world to do with what is ordinarily called "epigenetics" as
opposed to, for example "developmental biology". You seem to think
that anything and everything that happens in cells and tissues and
organs and organisms that does not immediately involved DNA must
necessarily be epigenetic in nature.

Please answer this question. Do you believe that all these things
that you call "epigenetics" are factors that can be inherited from
parent to offspring and are involved in the process we call
evolution?

I

.

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