Nerve gene “origin” in sponges =>Frontloading?

Berceuse

Sorry, but what is front-loading?

One example of frontloading is Christian Schwabe's "Genomic Potential Hypothesis". However, while it has been cited by C. Luskin and other ID proponents several years ago it doesn't appear on ID pages anymore. German Christian Democrat Chancelor Helmut Kohl viewed front-loading from the opposite direction

Entscheidend ist, was hinten rauskommt

sparc

I don’t think it’s necessarily an either-or ‘design or darwin’ question, since a large part of it depends on fitting it into the view.

That is certainly true.

From the design perspective, you have the development of biological traits and aspects that aren’t being fully exploited by the given organism, far in advance of organisms which can properly exploit them, in advanced enough of a state that a gene-swap with some of said ‘advanced’ organisms results in considerable functionality.

Again, true enough. Though I may quibble over the notion of 'aren't being fully exploited'. The sponge is using these genes in a way that makes it the best sponge it can be. It has no need of making the same nervous system as a eumetazoan. If the authors contention is correct (a big if) that the globular cells act as a kind of sensory nervous system, than these genes are performing the exact same function of directing sense cells in all three organisms tested. Winston Macchi

Berceuse, I believe it is the term used relating to the theory on how the information got there to produce the kinds of variations we see in nature. As in God put the info in the DNA and let nature take it's course. IRQ Conflict

"My perspective would be this is Darwinist heaven. A system already in use, modified in different organisms, but still related enough that some parts are exchangeable, kind of. Of course the Amq genes didn’t not work perfectly in flies or Xenopus." I don't think it's necessarily an either-or 'design or darwin' question, since a large part of it depends on fitting it into the view. From the design perspective, you have the development of biological traits and aspects that aren't being fully exploited by the given organism, far in advance of organisms which can properly exploit them, in advanced enough of a state that a gene-swap with some of said 'advanced' organisms results in considerable functionality. Or so I'd put it, reading over things. nullasalus

Sorry, but what is front-loading? Berceuse

I printed the paper out today at work (don't tell the boss) and I can summarize it for anyone who is interested. Intro -nerve cells originated early in eumetazoans after diversification from sponges and others (Cavalier-Smith et al, Can J Zoo, 1996) -sponges (Amphimedon queenslandica (Amq) in this paper) have orthologs of genes that play roles in neuron development and function, for example structural proteins (Sakarya et al, PLoS 2007) -co-option of these, along with the formation of many others provided components needed for postsynapse formation (Sakarya et al, PLoS 2007 -in Amq a subset of these structural proteins are expressed in a restricted cell type around the outer layer of the sponge larva (Sakarya et al, PLoS 2007) -they are akin to globular cells (Leys and Degnan, Biol Bull 2001) which migrate out of the subepithelium during embryogenesis to interact with the larval surface (this paper, supplemental) Results -tested to see if there were homologs of genes that direct eumetozoan specification (bHLH genes), and selection precursors (Notch genes) of these genes existed in Amq -Amq has 16 bHLH which they believe came from 1 precursor, AmqbHLH1 -Amq encodes 1 Notch receptor, AmqNotch and 5 Notch ligands, as well as others that have a role in Notch signalling -The characterized expression of AmqNotch, a ligand, and AmqbHLH - The are in in globular cells in the subepithelial layer that move to outer layer throughout development -They stay in globular cells only, not neighbors, and may direct them to the outer layer - may indicate that a mechanism of cell determination was operation in metazoan lineage prior to divergence -AmqbHLH is homologus to eumetozoan genes that are proneural and important -injected AmqbHLH mRNA into Xenopus embryos and found that it induces expression of N-tubulin (marker of neuronal development); leads to expression of the neurogenic gene X-Delta-1; is actively sensitive to lateral inhibition; interacts with a transcription factor to escape lateral inhibition -conclude AmqbHLH has proneural activity for sensory neurons -AmqbHLH can do more than some vertabrate genes it is similar to, but less as well (there are 10 homologs and it has activity that some don't, but there are activities that it cannot do) -expressed in fruit flys and saw similar effects, but seems to be related to a slightly different gene type in flies Conclusions -Amq's have some proneural genes, but not others, suggesting the response to AmqNotch is not enacted by the same molecules that initiate differentiation in the bilaterians -propose the process of neural differentiation emerged as an addition to the already established cell-differentiation program in operation in the metazoan lineage comprising bHLH and Notch genes in globular cells (which also express other components of what became the eumetazoan postsynapse (Sakarya et al, PLoS 2007)) -a globular cell may be receptive to environmental stimuli (based on supplemental figures which I'm sorry to say I did not print out)

We therefore propose that early metazoans were already in possession of "proto-neural" cells and that the functionality of these cells was based upon molecular secretion in response to environmental stimuli.

That last bit I imagine is the next paper. I should have realized that half of today's papers are supplemental, but if anyone is interested I can get it next week. My perspective would be this is Darwinist heaven. A system already in use, modified in different organisms, but still related enough that some parts are exchangeable, kind of. Of course the Amq genes didn't not work perfectly in flies or Xenopus. Winston Macchi

This experiment testifies to the fact that function can be separated from selection---as bFast said, "totally non-Darwinian." There's another article about a gene which can be replaced by two different similar type genes during development, and always resulting in perfectly normal development. The authors conclude that the "location" of the gene---not the exact same gene sequence---appears to be what is important. How Darwinian is that? What is evolution? Answer: changing gene frequencies. Not! Three or four years ago, on PT, I was making all kinds of predictions of what biologists would find, all predicated on ID principles, and they have all found confirmation since. The Darwinists say: "Oh, this is surprising." We say, "Of course, what would you expect." Yet, nonetheless, they remain cocksure of themselves. Go figure. PaV

Sorry Charlie, didn't see that bulge. bFast

The end of the abstract: "From these results, we infer that the bilaterian neurogenic circuit, comprising proneural atonal-related bHLH genes coupled with Notch-Delta signaling, was functional in the very first metazoans and was used to generate an ancient sensory cell type." Typical. The first metazoan ancestors of the sponges would have to have been considerably more complex, with more cell layers, and the sponges are degenerate remnants. Rather implausible, and can probably never be conclusively confirmed or denied, but it must be the truth because Darwinism can't ever be falsified. magnan

Darwinian gradulism has been falsified by observed biological evidence. Call the papers, I'm certain they will want to do a full page spread. Upright BiPed

Good catch DLH. "Totally unexpected surprising results" always translates to "just what evolution would have predicted." Charlie

bFast - I think Charlie has a big tongue shaped bulge in his cheek! DLH

Charlie, why would evolution have predicted that sponges, which don't have nervous systems, would have the proteins that make nervous systems? If this is just what evolution would have predicted, why did the researchers say, "something we never expected to find."? bFast

bFast, What do you mean? It's just what evolution would have predicted. Charlie

Thanks, DLH.

“But what was really cool,” he said, “is we took some of these genes and expressed them in frogs and flies and the sponge gene became functional — the sponge gene directed the formation of nerves in these more complex animals.

How non-darwinan is that! bFast