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Preadaptations

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« Reply #15 on: July 31, 2009, 12:14:43 PM »

More preadaptations:

The sea urchin is another interesting creature (Green circle, yellow circle = divergence time):

It provides valuable knowledge for cancer, Alzheimer's and infertility research:

Sea Urchins' Genetics Add To Knowledge Of Cancer, Alzheimer's And Infertility


What is even more interesting is what lurks in its genome. According to present models, they originated at least 450 million years ago. These organisms have no eyes, ears or a nose, yet they have the genes humans have for vision, hearing and smelling (see above link). They also have a surprisingly complex immune system, which surpasses the human one by far.

Now the genes in the genetic toolkit (nice video) in animals responsible for assigning specific properties of the various body parts are known as Hox genes. Here is a nice overview of Hox genes. A great deal of Hox genes are found in the sea urchin, the pattern of gene expression just differs, resulting in a different body plan.

Right at the base of the animal tree, a sundry of genes necessary for sight, smell, hearing as well as the various body plans were present in the genome of the common ancestor.

The Trichoplax adhaerens genome is equally intriguing. More coming...
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« Reply #16 on: August 03, 2009, 08:47:55 AM »

Pitx: Another neurologically associated Hox gene present in the Trichplax genome.

The various versions:
Trichoplax. Function unknown at present. Would be interesting to find out what it is.
Human Pitx1 Its function:
Quote
This gene encodes a member of the RIEG/PITX homeobox family, which is in the bicoid class of homeodomain proteins. Members of this family are involved in organ development and left-right asymmetry. This protein acts as a transcriptional regulator involved in basal and hormone-regulated activity of prolactin.

Human Pitx2 Its function:
Quote
This gene encodes a member of the RIEG/PITX homeobox family, which is in the bicoid class of homeodomain proteins. The encoded protein acts as a transcription factor and regulates procollagen lysyl hydroxylase gene expression. This protein plays a role in the terminal differentiation of somatotroph and lactotroph cell phenotypes, is involved in the development of the eye, tooth and abdominal organs, and acts as a transcriptional regulator involved in basal and hormone-regulated activity of prolactin. Mutations in this gene are associated with Axenfeld-Rieger syndrome, iridogoniodysgenesis syndrome, and sporadic cases of Peters anomaly. A similar protein in other vertebrates is involved in the determination of left-right asymmetry during development. Alternatively spliced transcript variants encoding distinct isoforms have been described

Human Pitx3 Its function:
Quote
This gene encodes a member of the RIEG/PITX homeobox family, which is in the bicoid class of homeodomain proteins. Members of this family act as transcription factors. This protein is involved in lens formation during eye development. Mutations of this gene have been associated with anterior segment mesenchymal dysgenesis and congenital cataracts.

Zebrafish Pitx1
Zebrafish Pitx2
Zebrafish Pitx3
Drosophila Ptx1 (fruitfly)

More interesting facts about Pitx:
The Pitx homeobox gene in Bombyx mori: Regulation of DH-PBAN  europeptide hormone gene expression
Quote
The diapause hormone-pheromone biosynthesis activating neuropeptide gene, DH-PBAN, is expressed exclusively in seven pairs of DH-PBAN-producing neurosecretory cells (DHPCs) on the terminally differentiated processes of the subesophageal ganglion (SG). To help reveal the regulatory mechanisms of cell-specific DH-PBAN expression, we identified a cis-regulatory element that regulates expression in DHPCs using the recombinant AcNPV-mediated gene transfer system and a gel-mobility shift assay. Bombyx mori Pitx (BmPitx), a bicoid-like homeobox transcription factor, binds this element and activates DH-PBAN expression. The BmPitx was expressed in various tissues, including DHPCs in the SG. Suppression of DH-PBAN expression by silencing of the BmPitx successfully induced non-diapaused eggs from a diapause egg producer. To the best of our knowledge, this report is the first to identify a neuropeptide-encoding gene as a target of the Pitx transcriptional regulator in invertebrates. Thus, it is tempting to speculate that functional conservation of Pitx family members on neuropeptide gene expression occurs through a combinational code mechanism in both vertebrate and invertebrate in neuroendocrine systems.


PITX genes are required for cell survival and Lhx3 activation

Zebrafish pitx3 is necessary for normal lens and retinal development.

And the trend of neurologically associated genes present before the emergence of neurons, eyes, body plans etc. continues...
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« Reply #17 on: August 03, 2009, 11:50:25 AM »

*Yawn*  “Well, I can’t explain it, therefore a greater intelligence must be at work.”

What a tired little joke.


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« Reply #18 on: August 03, 2009, 15:39:17 PM »

Don't worry, this wabbit can handle it...


Aaaanyway... more preadaptations Grin.

More about toolkits for eye development in animals with no eyes, present before the emergence of eyes... the Trichplax genome.
Six3 and Six6 activity is modulated by members of the groucho family.
Quote
Six3 and Six6 are two genes required for the specification and proliferation of the eye field in vertebrate embryos, suggesting that they might be the functional counterparts of the Drosophila gene sine oculis (so). Phylogenetic and functional analysis have however challenged this idea, raising the possibility that the molecular network in which Six3 and Six6 act may be different from that described for SO. To address this, we have performed yeast two-hybrid screens, using either Six3 or Six6 as a bait. In this paper, we report the results of the latter screen that led to the identification of TLE1 (a transcriptional repressor of the groucho family) and AES (a potential dominant negative form of TLE proteins) as cofactors for both SIX6 and SIX3. Biochemical and mutational analysis shows that the Six domain of both SIX3 and SIX6 strongly interact with the QD domain of TLE1 and AES, but that SIX3 also interacts with TLE proteins via the WDR domain. Tle1 and Aes are expressed in the developing eye of medaka fish (Oryzias latipes) embryos, overlapping with the distribution of both Six3 and Six6. Gain-of-function studies in medaka show a clear synergistic activity between SIX3/SIX6 and TLE1, which, on its own, can expand the eye field. Conversely, AES alone decreases the eye size and abrogates the phenotypic consequences of SIX3/6 over-expression. These data indicate that both Tle1 and Aes participate in the molecular network that control eye development and are consistent with the view that both Six3 and Six6 act in combination with either Tle1 and/or Aes.



And toolkits for forebrain neuronal development?
The LIM-homeobox gene Islet-1 is required for the development of restricted forebrain cholinergic neurons.

Quote
Forebrain cholinergic neurons modulate complex mammalian behaviors such as reward-related learning and cognitive functions. Although their dysfunction is implicated in various psychiatric and neurodegenerative diseases, the factors governing cholinergic neuron differentiation and diversity are mostly unknown. We tested the role of the LIM-homeobox gene Isl1 in the development of forebrain cholinergic neurons by conditionally deleting Isl1 using a Six3-cre transgene. A depletion of cholinergic interneurons in the dorsal and ventral striatum, and cholinergic projection neurons in the nucleus basalis is observed and is ascribed to an early and persistent defect in cholinergic neuron differentiation. Notably, cholinergic innervation to the neocortex is abolished, whereas that to the hippocampus is unaltered. The unique pattern of cholinergic hypoinnervation encountered is supported by the presence of cholinergic projection neurons in the medial septum, the magnocellular preoptic area, and the substantia innominata. Together, these results demonstrate the requirement for Isl1 in the development of restricted telencephalic cholinergic neurons and link the development of cholinergic neurons in anatomically disparate sites to Isl1 function.

Some of these sequences present in bacteria and archaea...

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« Reply #19 on: August 03, 2009, 21:07:26 PM »


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