PZ Myers posted Entry 2717 on November 13, 2006 01:55 PM.
Trackback URL: http://www.pandasthumb.org/cgi-bin/mt/mt-tb.fcgi/2709

sea_urchin_sm.jpg

Oh happy day, the Sea Urchin Genome Project has reached fruition with the publication of the full sequence in last week's issue of Science. This news has been all over the web, I know, so I'm late in getting my two cents in, but hey, I had a busy weekend, and and I had to spend a fair amount of time actually reading the papers. They didn't just publish one mega-paper, but they had a whole section on Strongylocentrotus purpuratus, with a genomics mega-paper and articles on ecology and paleogenomics and the immune system and the transcriptome, and even a big poster of highlights of sea urchin research (but strangely, very little on echinoderm development). It was a good soaking in echinodermiana.

Continue reading "The sea urchin genome" (on Pharyngula)

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Comment #143921

Posted by Matt Inlay on November 13, 2006 3:27 PM (e)

I haven’t read any of the material yet, but I just want to go on record to make a prediction that they’ll find components of the lectin pathway of complement activation. Check out my article in TalkDesign.org to find out why.

http://talkdesign.org/cs/?q=evolving_immunity

Comment #143928

Posted by PZ Myers on November 13, 2006 4:13 PM (e)

Here’s the relevant chunk of the paper. Does that help?

The complement system. The complement system of vertebrates is a complex array of soluble serum proteins and cellular receptors arranged into three activation pathways (classical, lectin, and alternative) that converge and activate the terminal or lytic pathway. This system opsonizes pathogenic cells for phagocytosis and sometimes activates the terminal pathway, which leads to pathogen destruction. An invertebrate complement system was first identified in the sea urchin [for reviews, see (39, 40)], and the analysis of the genome sequence presented a more complete picture of this important immune effector system. In chordates, collectins initiate the lectin cascade through members of the mannose-binding protein (MBP)–associated protease (MASP)/C1r/C1s family. Several genes encoding collectins, C1q and MBP, have been predicted (39) and were present in the genome; however, members of the MASP/C1r/C1s family were not identified. There was no evidence for the classical pathway, which links the complement cascade with immunoglobulin recognition in jawed vertebrates. The alternative pathway is initiated by members of the thioester protein family, which, in the sea urchin, was somewhat expanded with four genes. Two of the thioester proteins, SpC3 and SpC3-2, are known to be expressed, respectively, in coelomocytes and in embryos and larvae. Furthermore, there were three homologs of factor B, the second member of the alternative pathway (41).

The terminal complement pathway in vertebrates acts to destroy pathogens or pathogen-infected cells with large pores called membrane attack complexes (MACs). Twenty-eight gene models were identified that encode MAC- perforin domains, but none of these had the additional domains expected for terminal complement factors (C6 through C9). Instead, these are members of a novel and very interesting gene family with perforin-like structure. In vertebrates, perforins carry out cell-killing functions by cytotoxic lymphocytes through the formation of small pores in the cell membranes. If the complement system in the sea urchin functions through multiple lectin and alternative pathways in the absence of the lytic functions of the terminal pathway, the major activity of this system is expected to be opsonization.

Comment #143932

Posted by S. Dyllus on November 13, 2006 6:17 PM (e)

Does anyone really believe the complement system in the sea urchin functions through multiple lectin and alternative pathways in the ABSENCE of the lytic functions of the terminal pathway?

Comment #143936

Posted by Shalini, BBWAD on November 13, 2006 7:06 PM (e)

Only if you’re an IDiot.

(smirk)

Comment #143947

Posted by Coin on November 13, 2006 11:45 PM (e)

Does anyone really believe the complement system in the sea urchin functions through multiple lectin and alternative pathways in the ABSENCE of the lytic functions of the terminal pathway?

I don’t know what any of that means. Guess I’ve got a lot of reading to do :O

Truth be told, all I really know about any of this is that sea cucumbers defend themselves from predators by spitting out their internal organs at their enemy, then taking advantage of the resulting confusion to run away. That is the best superpower ever.

Comment #144015

Posted by 'Rev Dr' Lenny Flank on November 14, 2006 5:49 PM (e)

Truth be told, all I really know about any of this is that sea cucumbers defend themselves from predators by spitting out their internal organs at their enemy, then taking advantage of the resulting confusion to run away. That is the best superpower ever.

I was told by a friend of mine who is a scuba diver that one way to attract fish underwater is to find a sea cucumber and shake it back and forth to swish all the partially digested food out. It acts as bait.

We got on that subject after my friend described how his brother got sick and threw up underwater, while diving. That, um, attracted lots of fish too.

:)

Comment #144127

Posted by Henry J on November 15, 2006 2:02 PM (e)

That gives a whole other meaning to the term “seafood”…