On Fri, 27 Feb 2004 16:40:59 +0000 (UTC)
John Edser" edser{at}tpg.com.au wrote

NC:-
>As we all know, from 10-30,000 genes of the metazoan genome, several
>thousands,
>the so-called HOUSEKEEPING GENES,  are needed for the subsistence and
>reproduction of metazoan cells and are expressed some time during the
>lifetime
>of the cell. The rest, i.e. the majority of them are NONHOUSEKEEPING GENES,
>which perform extracellular, organismic functions and are expressed
>differentially in different types of cells. Their extracellular function
>determines the extracellular origin of signals for their expression, for no
>cell could figure out what the organism might need at any particular point
>in
>time (cell-cell interactions come to mind but they will later be dealt
>with).
>
>JE:-
>OK

>NC:-
..........................................................
>JE:-
>OK. Epigenetic control hierarchies exist which
>may be much larger within metazoan forms such that
>they can alter the phenotype expressed from the
>same set of genes.
>

Thus, you agree that the expression of nonhousekeeping genes, which are
responsible for cell differentiation and cell-cell interactions, is under
epigenetic (NONGENETIC) control. In view of the fact that all the stages of
metazoan reproduction (gametogenesis, early development and organogenesis)
depend on cell differentiatiion, it follows that this epigenetic system, or
these "epigenetic control hierarchies", regulates the individual
development in
metazoans.

>NC:-
>What we need to demonstrate is that all the stages of animal reproduction,
>starting with the formation of gametes and  individual development are under
>the  CNS control and regulation.
>
>JE:-
>I think you are arguing that the CNS is the last
>(highest)  epigenetic system that exists so that
>it has the power of direction of the phenotype.
>In my diagram this means the CNS would be E2
>where E2 is limited by E1 and E1 is limited by G.
>

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.

>JC:-
>Adequate experimental evidence already shows that the CNS (to be more exact,
>the integrated control system, which besides the CNS comprises the
>mechanisms
>for monitoring the status of the living system in general as well as the
>pathways for transmission to the cells all over the animal body of the
>epigenetic information  generated in neural circuits) controls and
>regulates:
>
>1. The formation of the egg and sperm cells
>
>2. The placement of maternal cytoplasmic factors in the egg cell.
>
>3. 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.
>
>4.The postphylotypic development, including the post-natal development (the
>development of secondary sexual characters etc.).
>
>JE:-
>Could you provide one example of each
>of the above?
>

"One example of each of the above" is a reasonable challenge, even though
examples abound. 



>1. The formation of the egg and sperm cells

a. In the female fire ant, Solenopsis invicta, the electrical activation of the
dopamine system resulting fromthe PROCESSING of an external stimulus (queen
pheromone) in the brain controls oogenesis and oviposition (Boulay et al 2000).
b. For more than two decades it is generally acknowledged that spermatogenesis
"is ultimately controlled by neurons in the CNS" (Sharp and Gow
1983) and that
the CNS exerts that control via the GnRH pulse generator and the
hypothalamic-pituitary-testicular axis (Vander).

>2. The placement of maternal cytoplasmic factors in the egg cell.

In the canary, Serinus  canaria, the seasonal changes  of photoperiod are
processed in the brain and via hypothalamic-pituitary-ovarian axis determine
the concentration of maternal testosterone in the egg (Schwabl, 1993).

>3. 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.

Since
-the parental CNS  regulates the placement of maternal cytoplasmic factors in
the egg cell, and
-maternal cytoplasmic factors  regulate the early development (Wolpert et al
1998; Hall 1998; Gilbert 2000, etc etc.)

-THE PARENTAL CNS(s) REGULATE THE EARLY DEVELOPMENT (since A regulates B and B
regulates C)

>4.The postphylotypic development, including the post-natal development (the
>development of secondary sexual characters etc.).

During embryogenesis the sensory neurons and Schwann cells secrete VEGF, which
determines the cell differentiation and patterning of arteries in their
vicinity what explains the old anatomic  observation on the general association
of arteries and peripheral nerves (Mukoyama et al. 2002).

One more example. For a long time it has been believed that the expression of
the  Sry gene on the chromosome Y induces the development of testes and
hormones secreted by testes determine the specific organization of the male
brain. Now we are told that the causal chain is the opposite: the sexual
differentiation of the brain starts before the expression of the Sry gene on
the chromosome Y, before the testes are formed and testosterone is secreted
(Dewing et al 2003). Recently (2003) in the Proc.Natl. Acad. Sci. USA, a
naturally occurring zebra finch was reported to be male (with testis) on the
right side and female (with an ovary) on the left, although genes and  the
circulating hormones are the same in both sides. Only brain circuits on the
right side are of different male patterning.

I believe the epigenetic system of heredity in metazoans is an obvious reality.
The examples presented here and numerous others clearly show that the
expression of nonhousekeeping genes and the main stages of individual
development are under control of an epigenetic control predicted by J. Maynard
Smith. 

Thank you for giving me the opportunity to argue and substantiate the existence
of this system. Further input and critical remarks from you, r. norman, and
others in the sbe are wellcomed and appreciated.
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