Preadaptations

[Phronesis]

Neurons and plant root cells may grow using a similar mechanism. And the protein responsible for this emerged way before neurons and plant root cells were present...

From Nerve Roots To Plant Roots: Research On Hereditary Spastic Paraplegia Yields Surprises

ScienceDaily (Aug. 10, 2009) — Sprouting. Branching. Pruning. Neuroscientists have borrowed heavily from botanists to describe the way that neurons grow, but analogies between the growth of neurons and plants may be more than superficial. A new study from the National Institutes of Health and Harvard Medical School suggests that neurons and plant root cells may grow using a similar mechanism.

The protein: Atlastin
Drosophila spastin regulates synaptic microtubule networks and is required for normal motor function.

The most common form of human autosomal dominant hereditary spastic paraplegia (AD-HSP) is caused by mutations in the SPG4 (spastin) gene, which encodes an AAA ATPase closely related in sequence to the microtubule-severing protein Katanin. Patients with AD-HSP exhibit degeneration of the distal regions of the longest axons in the spinal cord. Loss-of-function mutations in the Drosophila spastin gene produce larval neuromuscular junction (NMJ) phenotypes. NMJ synaptic boutons in spastin mutants are more numerous and more clustered than in wild-type, and transmitter release is impaired. spastin-null adult flies have severe movement defects. They do not fly or jump, they climb poorly, and they have short lifespans. spastin hypomorphs have weaker behavioral phenotypes. Overexpression of Spastin erases the muscle microtubule network. This gain-of-function phenotype is consistent with the hypothesis that Spastin has microtubule-severing activity, and implies that spastin loss-of-function mutants should have an increased number of microtubules. Surprisingly, however, we observed the opposite phenotype: in spastin-null mutants, there are fewer microtubule bundles within the NMJ, especially in its distal boutons. The Drosophila NMJ is a glutamatergic synapse that resembles excitatory synapses in the mammalian spinal cord, so the reduction of organized presynaptic microtubules that we observe in spastin mutants may be relevant to an understanding of human Spastin's role in maintenance of axon terminals in the spinal cord.

Atlastin, microtubules and synapses... Interesting.

Found in that critter without synapses yet emerged before the emergence of synapses... the trichoplax...

 

[Phronesis]

Inner Workings Of Molecular Thermostat Point To Pathways To Fight Diabetes, Obesity

ScienceDaily (Sep. 13, 2009) — Best known as the oxygen-carrying component of hemoglobin, the protein that makes blood red, heme also plays a role in chemical detoxification and energy metabolism within the cell. Heme levels are tightly maintained, and with good reason: Too little heme prevents cell growth and division; excessive amounts of heme are toxic.

So how long has heme been with us? Apparently since the LUCA...
Globin-coupled sensors, protoglobins, and the last universal common ancestor.

From the paper:

This protoglobin is thought to be present in organisms possibly as far back as the Last Universal Common Ancestor, or LUCA, the source of all life on Earth. LUCA is believed to have been a metabolically “flexible” single-celled organism with the ability to utilize oxygen for energy before free oxygen even existed in the air, thus preceding oxygenic photosynthesizers. The idea that an organism existed with the capacity to “breathe” O2 before there was a real need to, however, goes against the textbook viewpoint [45]. In his recent book [9], Nick Lane argues that LUCA likely made use of a hemoglobin-like protein to manage oxygen homeostasis and an antioxidant enzyme like superoxide dismutase (SOD) to protect itself. This hemoglobin would not have to deal with much oxygen at all, but rather very low levels of oxygen, perhaps similar to the role of leghemoglobin in nitrogen-fixing bacteria.

Another example of a preadaptation biasing future evolutionary pathways... This time and oxygen-utilizing preadaptation before the emergence of oxygenic photosynthesizers. This fits in nice with the observations that large parts of multicellular body plans being present before the emergence of multicelluar organisms.

The hedghog signaling pathway and the unfolding of multicellular body plans was bought on by life itself as a result of an increase in atmospheric oxygen pressure produced by oxygenic photosynthesizers. This increase in atmospheric oxygen in turn seemed to have unlocked the pathways to multicellular body plans (>3 cell types) and oxygen-utilizing preadaptations were already present.

 

[Phronesis]

Two interesting articles:
How the Microbial World Saved Evolution from the Scylla of Molecular Biology and the Charybdis of the Modern Synthesis

Safeguarding evolution seems to have become a "scientific anathema". Thank goodness for molecular biology.

pg 18

On the other hand, 20th-century microbiology did not have a concept of evolution. Indeed, for most of the century, the discipline didn’t even have a proper understanding of itself! Microbiology was defined by those problems for which microbial systems were useful, be they practical (e.g., medical) or in the service of the better-developed scientific disciplines such as biochemistry and molecular biology or otherwise. Until relatively recently, microbiology’s concern with evolution never went beyond the stage of idle speculation.
As for evolution, it had been developed from a phenomenological description centering around what was generally termed natural selection into the modern evolutionary synthesis through its union with Mendelian genetics. The modern evolutionary synthesis should have been the 20th century’s evolutionary bastion, the forefront of research into the evolutionary process. No such luck!
The basic understanding of evolution, considered as a process, did not advance at all under its tutelage. The presumed fundamental explanation of the evolutionary process, “natural selection,” went unchanged and unchallenged from one end of the 20th century to the other. Was this because there was nothing more to understand about the nature of the evolutionary process? Hardly! Instead, the focus was not the study of the evolutionary process so much as the care and tending of the modern synthesis. Safeguarding an old concept, protecting “truths too fragile to bear translation” is scientific anathema. (The quote here is Alfred North Whitehead’s, and it continues thus: “A science which hesitates to forget its founders is lost” [32].) What makes the treatment of evolution by biologists of the last century insufferable scientifically is not the modern synthesis per se. Rather, it is the fact that molecular biology accepted the synthesis as a complete theory unquestioningly— thereby giving the impression that evolution was essentially a solved scientific problem with its roots lying only within the molecular paradigm.
There you have it. An entire century spent studying biology without seriously addressing evolution, without assigning importance to the study of the evolutionary process. Our understanding of biology, of biological organization, far from being near complete (as molecularists would have us believe), seems still in its infancy.

Read the whole article. Quite interesting.

Between “design” and “bricolage”: Genetic networks, levels of selection, and adaptive evolution

Mmmm, seems like evolution is more biased, less random and more predictable than previously thought...

Evolution in more predictable than a bricoleur randomly throwing things together until it works.
It borrows from previous solutions as evidenced by preadaptations.
It is biased towards a few endpoints.
Evolutionary pathways tend to converge on similar solutions.

See any similarities?

 

[Phronesis]

There are many forms of cell death including apoptosis, autophagy, oncosis, metabolic catastrophe, mitotic catastrophe etc.

Apoptosis is an interesting form of programmed cell death. It plays crucial role during development. For example, during the development of the hand, there are weblike structures that from that make your hands look like frog feet. After a certain period, programmed cell death of these membranes between the fingers kicks in and signals the descrtruction of these cells so that your hand can be formed without them.

There are several regulatory pathways that regulate this pathway and it converges to a common caspase-dependent pathway. Caspases are cysteine proteases that cleave proteins, chopping them up and rendering them non-functional. Induction of executioner caspases results in the total, yet controlled destruction of a cell in a manner than allows it to be reabsorbed by other cells without causing inflamation.

Interesting thing about these caspases is that they are present way before the emergence of multi-cellular organisms e.g.:
Cell Death Occurs In Same Way In Plants And Animals

ScienceDaily (Oct. 21, 2009) — Research has previously assumed that animals and plants developed different genetic programs for cell death. Now an international collaboration of research teams, including one at the Swedish University of Agricultural Sciences, has shown that parts of the genetic programs that determine programmed cell death in plants and animals are actually evolutionarily related and moreover function in a similar way.

In both plant and animal cells that undergo programmed cell death, the protein TUDOR-SN is broken down. In pollen, from the model plant mouse-ear cress, a reduction in TUDOR-SN leads to fragmentation of DNA (red signal) and premature cell death. (Credit: Photo by Andrei P. Smertenko)
​

The findings were published in Nature Cell Biology October 11.
For plants and animals, and for humans as well, it is important that cells both can develop and die under controlled forms. The process where cells die under such forms is called programmed cell death. Disruptions of this process can lead to various diseases such as cancer, when too few cells die, or neurological disorders such as Parkinson's, when too many cell die.

The findings are published jointly by research teams at SLU (Swedish University of Agricultural Sciences) and the Karolinska Institute, the universities of Durham (UK), Tampere (Finland), and Malaga (Spain) under the direction of Peter Bozhkov, who works at SLU in Uppsala, Sweden. The scientists have performed comparative studies of an evolutionarily conserved protein called TUDOR-SN in cell lines from mice and humans and in the plants norway spruce and mouse-ear cress. In both plant and animal cells that undergo programmed cell death, TUDOR-SN is degraded by specific proteins, so-called proteases.

The proteases in animal cells belong to a family of proteins called caspases, which are enzymes. Plants do not have caspases – instead TUDOR-SN is broken down by so-called meta-caspases, which are assumed to be ancestral to the caspases found in animal cells. For the first time, these scientists have been able to demonstrate that a protein, TUDOR-SN, is degraded by similar proteases in both plant and animal cells and that the cleavage of TUDOR-SN abrogate its pro-survival function. The scientists have thereby discovered a further connection between the plant and animal kingdoms. The results now in print will therefore play a major role in future studies of this important protein family.

Cells that lack TUDOR-SN often experience premature programmed cell death. Furthermore, functional studies at the organism level in the model plant mouse-ear cress show that TUDOR-SN is necessary for the development of embryos and pollen. The researchers interpret the results to mean that TUDOR-SN is important in preventing programmed cell death from being activated in cells that are to remain alive.

The research teams maintain that the findings indicate that programmed cell death was established early on in evolution, even before the line that led to the earth's multicellular organisms divided into plants and animals. The work also shows the importance of comparative studies across different species to enhance our understanding of how fundamental mechanisms function at the cellular level in both the plant and animal kingdoms, and by extension in humans.

Let's see, so far things needed for the emergence of multi-cellularity that was present before multi-cellular organisms:
Toolkit for multi-cellularity
Programmed cell death
Calcium signaling toolkits
Adherens junctions
Complex Tyrosine Kinase signaling pathways
Parts of the nervous system, neurotransmitters, receptors etc.
Body plan tool kits.
And many more.

Interesting not?

 

[Jenemesis]

VERY interesting!
fascinating
beyond comprehension

 

[HapticSimian]

VERY interesting!
fascinating
beyond comprehension

So, you find the study of preadaptations, an integral part of evolution which you idiotically reject, fascinating?

That's... fascinating...

 

[Phronesis]

So, you find the study of preadaptations, an integral part of evolution which you idiotically reject, fascinating?

That's... fascinating...

Instead of saying "preadaptations" is an integral part of evolution and then proceed to insult other people, why don't you just contribute in a constructive manner?
That is also fascinating.

 

[HapticSimian]

Instead of saying "preadaptations" is an integral part of evolution and then proceed to insult other people, why don't you just contribute in a constructive manner?
That is also fascinating.

You really do need to loosen up a bit - this is a forum for discussion, after all. Stating fact about someone else's opinion on a matter can not be deemed insulting, it is an empirical observation.

As for the encompassing discussion regarding preadaptations, you're doing a fine job of supplying the factual elements.

/derail

 

[Jenemesis]

My understanding of bilogical complexities is very limited, although I have an interest and an awe of the science, which in itself fortifies my respect and humility, this fascination is not for the intelligence of the self-induced adaptations of the phenomenon accredited to evilution but the certainty that so much detail and complexity defies such self-initiating "intelligence" built into the design of living things. Sybiosis, let alone life itself, could never have pre-empted its existence let alone adaptations.
Such intricate detail could never be self-induced by any collective cells' self-willing with so much "luck" no matter what amount of time is concocted to justify it, in actual fact, the adding of trillions of years make the cells' clairvouyant also, which makes the phenomenon even more unbelievable to say the least.
Yes, it is absolutely fascinating indeed!
There are built in adaptations but they are always there, inherent, latent for when the conditions require them, not suddenly cococted after a convening of the DNA to decide to do so.

 

[NoLimit]

Such intricate detail could never be self-induced by any collective cells' self-willing with so much "luck" no matter what amount of time is concocted to justify it, in actual fact, the adding of trillions of years make the cells' clairvouyant also, which makes the phenomenon even more unbelievable to say the least.

There is some similarity between the evolution theory and the belief in a God. Both are complex and ambitious in trying to convey and sound plausible. One because it has taken up the challenge to try and piece together the past from a molecular level and model randomness. The other as it relies on a unquestioning leap of faith to accede to, in the face of tangible evidence to the contrary. One relies on appealing to the discerning and the other to the gullible. Which has a greater chance of success?

Evolution will make in-roads and perhaps reach a critical mass whereby 'luck' can be explained. Belief in God on the other hand with its 'have faith' will remain stagnant and implausible as ever.

 

[Phronesis]

More about TrichoplaX Adherens, that critter that looks like a flattened blob with only four cell types. There are no nerve cells, sensory cells, muscle cells, bone cells etc.

Trichoplax adhaerens, the animal at the base of the evolutionary tree with a sundry of neurologically associated Hox genes. It has only four cell types, excluding nerve, motor neurons, muscles, arteries, bone.​

Look at the genes:
Nuclear receptor = 4, including Hnf4, retinoid X receptor, Nr2 and one other.
Sox (SRY-related HMG-box) genes = 6, including Sox8/10/E, Sox2/3, three other Sox and Tcf/Lef
TALE-class related genes = 3, including Pbx/Exd, Irx and Meis

Let's look at Sox 3, Pbx, Meis and retinoid X receptor.
A recent article from the Biochemical Journal (access is free):
PBX1 and MEIS1 up-regulate SOX3 gene expression by direct interaction with a consensus binding site within the basal promoter region

From the article:
1) Sox/SOX genes are key players in the regulation of embryogenesis
and nervous system development.
2) Sox3 direct gonadal development, brain formation and cognitive function.
3) Pbx genes play a central role in development and organogenesis.
4) Meis also plays a crucial role during embryonic development.
5) Pbx activity is regulated by Meis.
6) And Pbx and Meis regulate SOX3 gene expression
7) The data presented in the article suggests that that Pbx and
Meis enhances Sox3 gene responsiveness to retinoic acid by directly interacting to a binding site upstream of a retinoid X receptor (alpha) regulatory element.

So, there you have it, Pbx, Meis, Sox, retinoic acid and retinoid X receptor elements together control neuronal differentiation and maturation during nervous system development.
These genes were present in an organism that is at the base of the eukaryotic evolutionary tree with no nerves and no sensory cells.
Fascinating not?

 

[Phronesis]

Novel Evolutionary Theory For The Explosion Of Life

ScienceDaily (Oct. 27, 2009) — The Cambrian Explosion is widely regarded as one of the most relevant episodes in the history of life on Earth, when the vast majority of animal phyla first appear in the fossil record. However, the causes of its origin have been the subject of debate for decades, and the question of what was the trigger for the single cell microorganisms to assemble and organize into multicellular organisms has remained unanswered until now.

Within a longstanding research collaboration between the Institute for Bioengineering of Catalonia and Bielefeld University together with the Friedrich-Miescher-Institute in Basel and the Marine Biological Laboratory at Woods Hole (Massachusetts), Xavier Fernàndez-Busquets (Barcelona) and Dario Anselmetti (Bielefeld) and their colleagues published online in the journal Molecular Biology and Evolution their biophysical single molecule results on the effect of calcium on the interactions of cell adhesion molecules from marine sponges. These simply organized organisms do not have specialized muscle or nerve cells and nevertheless survived the last 500 million years almost unchanged and are considered a link between the single-cell dominated Precambrian and later multicellular organisms.
The researchers succeeded to show that the massive and sudden surge in the calcium concentration of the Cambrian seawater -- that is believed to be the result of volcanically active midocean ridges -- not only initiated the buildup of calcified shells, but was also mandatory for the aggregation and stabilisation of multicellular sponge structures. This allows, on the other hand, to formulate a novel theory where the geologically induced increase of marine calcium might be the key for understanding the Cambrian Explosion of Life.
This paper constitutes the first research work where single molecule force spectroscopy studies have provided meaningful answers to such a deep evolutionary biology question as the origin of multicellular animals, and might represent a milestone for both disciplines and an example of how multidisciplinarity and collaboration are essential components of excellent contemporary science.

What a nice discovery. Let's look at the tree of life:

1) The emergence of multicellular life occurred at around 600 million years.
2) Components of the multicellular signaling pathway (sonic-hedgehog) were present in ancestral lineages way before the emergence of multi-cellularity.
3) The origin of multi-cellular body plans roughly coincide with an increase in atmospheric oxygen pressure as well as the first bona fide hedgling.
4) Hedglings are the only examples of post-translational sterolation (addition of cholesterol) of proteins in contempory biology and oxygen is needed for cholesterol synthesis, more importantly, oxygen is needed for placing the hydroxyl group in the 3-position of cholesterol which plays a crucial role in subsequent transformations (including sterolation).
5) While large parts of the hedgehog-signaling pathway was present, a little extra oxygen was needed to unlock multicellular signaling capabilities of hedglings.
6) The increase in atmospheric oxygen was bought on about by life itself and this increase in atmospheric oxygen in turn seemed to have unlocked the pathways to multicellular body plans
7) Oxygen is Key To 'Cut And Paste' Of Genes and the genes that perform these functions (protein hydroxylases or histone demethylases) were present way before oxygen was present in large quantities. Present in proteobacteria.

And now, increased calcium concentration also played a role in the emergence of multicellularity. Why is this interesting? Well, have a look at the preadaptations in the genome of the choanoflagellate, Monosiga brevicollis (A unicellular organism.

Choanoflagellates (link) are single-celled organisms thought to be most closely related to animals. The divergence time of this organism was about >600 million years ago (see above).

Calcium signaling toolkits also play a crucial role in multicellular signaling. Calcium signaling plays a crucial part in contraction, metabolism, secretion, neuronal excitability, cell death, differentiation and proliferation. Thus, it is o interesting to note that Monosiga brevicollis has an extensive calcium signaling toolkit and emerged before the evolution of multicellular animals.

Another interesting fact about the genome of the Monosiga brevicollis is noted in this article.

Interestingly, the choanoflagellate has nearly as many introns - non-coding regions once referred to as "junk" DNA - in its genes as humans do in their genes, and often in the same spots. Introns have to be snipped out before a gene can be used as a blueprint for a protein and have been associated mostly with higher organisms.

The choanoflagellate genome, like the genomes of many seemingly simple organisms sequenced in recent years, shows a surprising degree of complexity, King said. Many genes involved in the central nervous system of higher organisms, for example, have been found in simple organisms that lack a centralized nervous system.

Likewise, choanoflagellates have five immunoglobulin domains, though they have no immune system; collagen, integrin and cadherin domains, though they have no skeleton or matrix binding cells together; and proteins called tyrosine kinases that are a key part of signaling between cells, even though Monosiga is not known to communicate, or at least does not form colonies.

(Emphasis mine)


Looks like pre-existing, latent potential was unlocked by increased in calcium and oxygen concentrations on earth...

 

[Phronesis]

Talk about constrained/biased/restricted evolution.... towards a few ends.

Venomous Shrew And Lizard: Harmless Digestive Enzyme Evolved Twice Into Dangerous Toxin In Two Unrelated Species

ScienceDaily (Nov. 2, 2009) — Biologists have shown that independent but similar molecular changes turned a harmless digestive enzyme into a toxin in two unrelated species -- a shrew and a lizard -- giving each a venomous bite.

Guess "Darwin was right. Up to a point"

 

[Phronesis]

Echolocation and Prestin (the protein )
Prestin is a transmembrane protein (10-12 transmembrane domains) with the ability to convert a change in membrane potential into a mechanical force (Gleitsman et al., 2009). It is a "direct voltage-to-force converter" and plays a crucial role in sound amplification in various organisms and thus play an important part in an organism's ability to sense sound waves (Dallos and Fakler, 2002, Li et al., 2010). What does the protein look like? From Dallos and Fakler, 2002 (Figure 1).

Figure 1: Prestin protein. From Dallos and Fakler, 2002.​

Recent studies suggest that not only echolocating, but the Prestin gene that plays a role in echolocation, converged in several different species (different species of bats, dolphins, toothed whales) to perform the same function with convergent changes in the coding DNA of the gene (Li et al., 2010, Teeling, 2009).

Interestingly, the Prestin gene is found in an organism (Trichoplax adhaerens) with no nerve cells, sensory cells or muscle cells. Trichoplax adhaerens emerged before biletarians, way before any organisms without any sound sensing organs (Figure 2

Figure 2: Tree of life (Adapted from discoverlife.org)
​

The organism only has four cell types (Figure 3).

Figure 3: Link​

So what is the Prestin gene doing in the genome of an organism with no hearing apparatus or nervous system and emerged long before these kinds of organisms or organs for sound wave mechanosensing?

Perhaps echolocation relies on a common design? Well these guys say so....

I donno about that (sounds like the words of IDiots, but I digress), perhaps the manifestation of echolocation relies on a distinct form of matter....the coding of Prestin? The emergence of this protein form just guaranteed that echolocation was on the cards over vast evolutionary time scales even though it was present way before echolocation even played an important role in nature.

Or..., maybe this is just another example of irreducible composites of form (echolocation) and matter (prestin) that resulted in echolocating organisms? How deep does the rabbit hole go?

 

[Phronesis]

Check out this critter. Probably emerged about 1.5 billion years ago.
Plodding Amoeba Flips Into Free-Swimming Flagellate: Naegleria Genome Sheds Light on Transition from Prokaryotes to Eukaryotes

op: N. gruberi flagellate-stage (microtubules are highlighted in green, basal bodies in red, and DNA is stained blue). Bottom: N. gruberi, amoeba-stage. (Credit: Photos by Lillian Fritz-Laylin, UC Berkeley)​

What lurks in its genome? Synapsin.

Look for yourself:
Go here
Select protein (above the seach text bar)
Search for Synapsin
Click on any organism's prestin protein (e.g. Synapsis [Homo Sapiens])
Click FASTA
Copy the sequence
Then go here
Click BLAST
Select Blastp (In alignment program)
Paste sequence into box and submit job
Then click on the best hit and you should get this and this

Highly similar sequences.

What does synapsin do?

This gene is a member of the synapsin gene family. Synapsins encode neuronal phosphoproteins which associate with the cytoplasmic surface of synaptic vesicles. Family members are characterized by common protein domains, and they are implicated in synaptogenesis and the modulation of neurotransmitter release, suggesting a potential role in several neuropsychiatric diseases. This member of the synapsin family plays a role in regulation of axonogenesis and synaptogenesis. The protein encoded serves as a substrate for several different protein kinases and phosphorylation may function in the regulation of this protein in the nerve terminal. Mutations in this gene may be associated with X-linked disorders with primary neuronal degeneration such as Rett syndrome. Alternatively spliced transcript variants encoding different isoforms have been identified.

Mmm, a protein necessary for neuronal functioning existed millions of years before organisms with anything resembling a nervous system.

Guess a potentiality was actualized over time. Interesting not?

 

[Phronesis]

Ah, and look at all the primitive information storage and processing machinery present in this organism:

Figure 6 Ancient Origin and Innovation in Eukaryotic Proteins

Schematics of the four scenarios of protein origin we consider are along the bottom and color-coded in the charts: ancient (blue), novel (green), addition of a eukaryote-specific protein domain (orange), and eukaryotic-specific fusion of two domains (red). The protein families that could be categorized are presented in (A) overview pie charts comparing the origins of protein families in ancient eukaryotes (top) and animals (bottom, from Putnam et al., 2007) and (B) stacked barcharts showing subsets of the ancient eukaryotic families divided by KOG function, omitting unknown and general KOG functions. prok, prokaryotic (i.e., archaeal and/or bacterial); euk, eukaryotic; Post-trans., post-translational. See also Tables S4, S19, S20, S21, S22, and S23.​

 

[Phronesis]

Another protein for vision.... emerged waaaaay before eyes were present.

Scientists Discover 600 Million-Year-Old Origins of Vision

ScienceDaily (Mar. 12, 2010) — By studying the hydra, a member of an ancient group of sea creatures that is still flourishing, scientists at UC Santa Barbara have made a discovery in understanding the origins of human vision.

This is a hydra, an ancient sea creature that flourishes today. (Credit: Todd Oakley, UCSB)​

The finding is published in the Proceedings of the Royal Society B, a British journal of biology.

Hydra are simple animals that, along with jellyfish, belong to the phylum cnidaria. Cnidarians first emerged 600 million years ago.

"We determined which genetic 'gateway,' or ion channel, in the hydra is involved in light sensitivity," said senior author Todd H. Oakley, assistant professor in UCSB's Department of Ecology, Evolution and Marine Biology. "This is the same gateway that is used in human vision."

Oakley explained that there are many genes involved in vision, and that there is an ion channel gene responsible for starting the neural impulse of vision. This gene controls the entrance and exit of ions; i.e., it acts as a gateway.

The gene, called opsin, is present in vision among vertebrate animals, and is responsible for a different way of seeing than that of animals like flies. The vision of insects emerged later than the visual machinery found in hydra and vertebrate animals.

"This work picks up on earlier studies of the hydra in my lab, and continues to challenge the misunderstanding that evolution represents a ladder-like march of progress, with humans at the pinnacle," said Oakley. "Instead, it illustrates how all organisms -- humans included -- are a complex mix of ancient and new characteristics."

David Plachetzki, who received his Ph.D. for work done in the Oakley lab, is the first author. Plachetzki is now a postdoctoral fellow at UC Davis. UCSB undergraduate Caitlin R. Fong is the second author of the paper.

 

[Techne]

Components for the nervous system were present before the emergence of nerves...scientists are surprised:
Sodium Channels Evolved Before Animals’ Nervous Systems, Research Shows

An essential component of animal nervous systems—sodium channels—evolved prior to the evolution of those systems, researchers from The University of Texas at Austin have discovered.

“The first nervous systems appeared in jellyfish-like animals six hundred million years ago or so,” says Harold Zakon, professor of neurobiology, “and it was thought that sodium channels evolved around that time. We have now discovered that sodium channels were around well before nervous systems evolved.”

Quite fascinating!

Zakon and his coauthors, Professor David Hillis and graduate student Benjamin Liebeskind, published their findings this week in PNAS.

Nervous systems and their component neuron cells were a key innovation in the evolution of animals, allowing for communication across vast distances between cells in the body and leading to sensory perception, behavior and the evolution of complex animal brains.

Sodium channels are an integral part of a neuron’s complex machinery. The channels are like floodgates lodged throughout a neuron’s levee-like cellular membrane. When the channels open, sodium floods through the membrane into the neuron, and this generates nerve impulses.

Zakon, Hillis and Liebeskind discovered the genes for such sodium channels hiding within an organism that isn’t even made of multiple cells, much less any neurons. The single-celled organism is a choanoflagellate, and it is distantly related to multi-cellular animals such as jellyfish and humans.

The researchers then constructed evolutionary trees, or phylogenies, showing the relationship of those genes in the single-celled choanoflagellate to multi-cellular animals, including jellyfish, sponges, flies and humans.

Because the sodium channel genes were found in choanoflagellates, the scientists propose that the genes originated not only before the advent of the nervous system, but even before the evolution of multicellularity itself.

“These genes were then co-opted by the nervous systems evolving in multi-cellular animals,” says Hillis, the Alfred W. Roark Centennial Professor in Natural Sciences. “This study shows how complex traits, such as the nervous system, can evolve gradually, often from parts that evolved for other purposes.”

“Evolutionarily novel organs do not spring up from nowhere,” adds Zakon, “but from pre-existing genes that were likely doing something else previously.”

Liebeskind, a graduate student in the university’s ecology, evolution and behavior program, is directing his next research efforts toward understanding what the sodium channels do in choanoflagellates.

 

[porchrat]

Components for the nervous system were present before the emergence of nerves...scientists are surprised:
Sodium Channels Evolved Before Animals’ Nervous Systems, Research Shows


Quite fascinating!

I don't get why they're so surprised. Sodium channels have more functions than just the depolarisation in nervous impulses. It makes perfect sense that sodium channels would have been around for a while before neurons showed up.

 

[Techne]

There are different kinds of sodium channels. E.g. ligand-gated and voltage-gated. I think they are referring to the voltage-gated ones which are associated with the nervous system.
The research article: Evolution of sodium channels predates the origin of nervous systems in animals
Abstract:

Voltage-dependent sodium channels are believed to have evolved from calcium channels at the origin of the nervous system. A search of the genome of a single-celled choanoflagellate (the sister group of animals) identified a gene that is homologous to animal sodium channels and has a putative ion selectivity filter intermediate between calcium and sodium channels. Searches of a wide variety of animal genomes, including representatives of each basal lineage, revealed that similar homologs were retained in most lineages. One of these, the Placozoa, does not possess a nervous system. We cloned and sequenced the full choanoflagellate channel and parts of two placozoan channels from mRNA, showing that they are expressed. Phylogenetic analysis clusters the genes for these channels with other known sodium channels. From this phylogeny we infer ancestral states of the ion selectivity filter and show that this state has been retained in the choanoflagellate and placozoan channels. We also identify key gene duplications and losses and show convergent amino acid replacements at important points along the animal lineage.