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Jason Cawley
Wolfram Science Group
Phoenix, AZ USA

Registered: Aug 2003
Posts: 712

Early life complexity paper in Nature

A recent empirical paper in Nature reports high genetic complexity in a family of genes thought to be responsible for body plan, in a sea anemone (within cnidaria), which diverged from modern forms using the same family at a time predating the Cambrian explosion by 100 Myr. The article understates how interesting this is, but it deservedly made the cover.

Why interesting? Because it suggests the basic "engine" responsible for body shape variety was not evolved late, nor even during the Cambrian, but was already present before that. The authors speculate (at the end) that a whole machinery was there for multicellular organism variety, and that the only specifically new addition in the Cambrian might be "an expansion of transcription factor families".

What is the NKS connection? Only that the motor of variety in body plans so evident later on may well be a simple algorythmic consequence of the sort of program needed to make quite primitive forms. Rather than something specifically selected for over extensive periods. Indeed, some later varieties appear to be simplifications (insects using 8 of 11 of the identified genes in the same family, e.g.)

In short, they may have found the underlying complexity "motor" that the Cambrian "variety timing" pattern has long suggested had to be there. Very simple factors governing growth and differentiation - rules that go way back - may be all that are required to generate a wide variety of body plans, by differential activation of different subsets, at various points (in time and in location) in an animal's growth.

The article is entitled "Unexpected complexity of the Wnt gene family in a sea anemone". A large list of 11 authors are on the paper - Arne Kusserow, Kevin Pang, Carsten Sturm, Martina Hrouda, Jan Lentfer, Heiko Schmidt, Ulrich Technau, Arndt von Haeseler, Bert Hobmayer, Mark Q. Martindale, and Thomas W. Holstein. It is in the "letters to Nature" section of the January 13 issue, and appears on the cover as "Evolution of Complexity".

Here is their abstract -

The Wnt gene family encodes secreted signalling molecules that control cell fate in animal development and human diseases. Despite its significance, the evolution of this metazoan-specific protein family is unclear. In vertebrates, twelve Wnt subfamilies were defined, of which only six have counterparts in Ecdysozoa (for example, Drosophila and Caenorhabditis). Here, we report the isolation of twelve Wnt genes from the sea anemone Nematostella vectensis, a species representing the basal group within cnidarians. Cnidarians are diploblastic animals and the sister-group to bilaterian metazoans. Phylogenetic analyses of N. vectensis Wnt genes reveal a thus far unpredicted ancestral diversity within the Wnt family. Cnidarians and bilaterians have at least eleven of the twelve known Wnt gene subfamilies in common; five subfamilies appear to be lost in the protostome lineage. Expression patterns of Wnt genes during N. vectensis embryogenesis indicate distinct roles of Wnts in gastrulation, resulting in serial overlapping expression domains along the primary axis of the planula larva. This unexpectedly complex inventory of Wnt family signalling factors evolved in early multi-cellular animals about 650 million years (Myr) ago, predating the Cambrian explosion by at least 100 Myr (refs 5, 8). It emphasizes the crucial function of Wnt genes in the diversification of eumetazoan body plans.

For those with Nature subscriptions, here is link to get the full text or a PDF -

http://www.nature.com/cgi-taf/dynap...7022/index.html

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Old Post 01-17-2005 05:57 PM
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Ricardo Azevedo
University of Houston

Registered: Jan 2005
Posts: 1

A very interesting paper. You might also be interested in the adjacent paper (pp. 152-156; download from http://wwworm.biology.uh.edu/publications/azevedo05.pdf). In it, we introduce a measure of the algorithmic complexity of developmental programs.

Ricardo Azevedo

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Old Post 01-20-2005 11:15 PM
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