Sodium Channels Evolved Before Animals’ Nervous Systems

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.”

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.

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.

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.

HERE 

Michael Ruse Has It All Figured Out

Philosopher Michael Ruse objects to a recent comment from Pope Benedict:

“If man were merely a random product of evolution in some place on the margins of the universe, then his life would make no sense or might even be a chance of nature. But no, reason is there at the beginning: creative, divine reason.”

According to Ruse, this view is a no-no because it contradicts science.  To show this, he, well, quotes from Stephen Jay Gould:

“Since dinosaurs were not moving toward markedly larger brains, and since such a prospect may lie outside the capabilities of reptilian design, we must assume that consciousness would not have evolved on our planet if a cosmic catastrophe had not claimed the dinosaurs as victims. In an entirely literal sense, we owe our existence, as large and reasoning mammals, to our lucky stars.”

Well, that just settles it once and for all. He then adds:

Gould was not saying that human evolution was uncaused or random in that sense. But he was saying that there is no design. Human evolution had no more forethought than, say, the pattern that a pile of sand makes when emptied from a bucket.

Yeah, I understand the argument and position, but where are the actual data that show “there is no design” and there was no, NO, NO foresight involved in human evolution?

Organizing the Cell

I’ve long suggested that life is a form of carbon-based nanotechnology, as the more we learn about the cell, the more sophisticated it becomes.  Doubt me?  Take 30 minutes and listen to the following lecture by microbiologist Lucy Shapiro as she describes how various events in the cell cycle in the simplest of cells is carried out.  Among other things, you’ll learn about the importance of location and organization inside bacteria, you’ll learn that the bacterial chromosome is laid out in space in an organized fashion, you’ll see the ingenious method the cell uses to target the site where it splits into two, and see how epigenetics is used to control the whole process.  Or at the very least, you’ll feel a little bit smarter for investing that half-hour of your life.

Urea cycle in diatoms

Building on that work, Allen and colleagues explored the evolutionary history of diatoms, specifically P. tricornutum, and cellular mechanisms for nutrient utilization in the environment, leading to the finding that diatoms have a functional urea cycle.

This was a stunning discovery, says Allen, because it was thought that the urea cycle originated with the metazoan (animal) branch of life.

There it has played an important role in facilitating a wide range of physiological innovations in vertebrates.

For example, urea synthesis enables rapid control of minerals and salts in the blood in animals such as sharks, skates, rays and bony fish, and ammonia detoxification associated with water retention in amphibians and mammals.

The latter was likely a prerequisite for life on land, and subsequently enabled the biochemical pathways necessary for processing a high-protein diet.

Allen and others have now shown that the urea cycle originated hundreds of millions of years before the appearance of metazoans.

HERE

Another brain protein with deep homology

Here is something that is pretty neat:

The size and shape of the human cerebral cortex, an evolutionary marvel responsible for everything from Shakespeare’s poetry to the atomic bomb, are largely influenced by mutations in a single gene, according to a team of researchers led by the Yale School of Medicine and three other universities.

The researchers found that mutations in the same gene, centrosomal NDE1, which is involved in cell division, were responsible for the deformity.

“The degree of reduction in the size of the cerebral cortex and the effects on brain morphology suggest this gene plays a key role in the evolution of the human brain,” said Murat Gunel, co-senior author of the paper and the Nixdorff-German Professor of Neurosurgery and professor of genetics and neurobiology at Yale.

“These findings demonstrate how single molecules have influenced the expansion of the human cerebral cortex in the last five million years,” Gunel said.

So here is a gene, Nde1, that has played a key role in the enlargement of the brain during human evolution.  As the article notes, Nde1 is part of the centrosome, an organelle that functions to organize the microtubules throughout the cell.  The function of Nde1 is not well characterized, but it is known to play a role in mitosis and neuron migration.  So it makes sense that a crippled version of Nde1 might exhibit deficient levels of cell division and neuron migration, explaining the small brained phenotype.

So when did Nde1 arise?