The genome of a sea anemone has been published, and of all things, this lowly animal has genes common to vertebrates, even humans. Science Daily began with a conundrum, “The first analysis of the genome of the sea anemone shows it to be nearly as complex as the human genome, providing major insights into the common ancestor of not only humans and sea anemones, but of nearly all multi-celled animals.” UC Berkeley’s Center for Integrative Genomics deciphered the genome and published the results in Science.1 “Surprisingly, the team found that the genome of the starlet sea anemone, which is lumped with jellyfish and corals into the earliest diverging eumetazoan phylum, Cnidaria, resembles the human and other vertebrate genomes more than it resembles the genomes of such well-studied ‘lab rats’ as fruit flies and nematode worms.” The starlet sea anemone, Nematostella vectensis, is just a few inches in diameter and has about 16 to 20 tentacles. It lives in brackish lagoons and marshes and feeds on passing nutrients. It’s not just that this creature’s genome is as complex as that of humans that was surprising. It has a comparable gene number, and, “Many of the anemone’s genes lie on its 30 chromosomes in patterns similar to the patterns of related genes on the 46 chromosomes of humans.” Nicholas Putnam of the Joint Genome Institute (JGI) of the Department of Energy said, “Many genes close together in the sea anemone are still close together in humans, even after six or seven hundred million years.” A story entitled, “Surprises in the sea anemone genome,” from The Scientist, added another anemone-human connection: “The researchers also discovered that exon-intron structure is very similar between modern vertebrates and sea anemones. Both have intron-rich genomes and about 80% of intron locations are conserved between humans and anemones.” Insects, by contrast, have a 50 to 80% dissimilarity from humans in their intron patterns. Science Daily added, “This similarity is present in the sea anemone and human genomes, despite the obvious differences between the two species.” The original paper commented on the “extensive” amount of conserved linkage with muted astonishment, “This is a notable total, given that any chromosomal fusions and subsequent gene order scrambling on either the human or Nematostella lineage during their ~700 million years of independent evolution would attenuate the signal for linkage.” The team also found that the sea anemone possesses about 1500 novel genes, unique to this animal compared with other eukaryotic groups. A consequence of the study for evolutionists is that complexity must be assumed to have been present farther back in time, back in the Cambrian when the basic body plans of animals are first seen in the fossil record. According to the team’s analysis, “The ancestral eumetazoan already had the genetic ‘toolkit’ to conduct basic animal biochemistry, development and nerve and muscular function,” Science Daily said. Putnam explained, “Basically, the sea anemone has all the basic mechanisms of interacting with the outside world seen in more morphologically complex creatures.” These traits appeared abruptly and have persisted ever since. Not only that, the exon-intron structure, chromosome positions and other similarities not usually associated with natural selection would have been conserved (i.e., unevolved) since the beginning of metazoan animal life. As could be expected, evolutionists are trying to make the most of these surprises and claiming they are “shedding light on evolution”. Elisabeth Pennisi used that line, titling her commentary in the same issue of Science, “Sea Anemone Provides a New View of Animal Evolution.”2 Daniel Rokhsar (UC Berkeley) said, “Anything the sea anemone has that also is found in humans, flies, snails or any other eumetazoans must already have been present in the common ancestor of eumetazoans.” Why, then, did more advanced organisms like flies and nematodes lack many of these genes? It’s “because both the anemone and vertebrate genomes have retained many ancestral genes that flies and nematode worms apparently lost over time,” Putnam said. “The genes of flies and worms also have been jumbled up among the chromosomes, making it hard to track genes through evolution.” This does not explain, however, why over much longer periods of time these genes did not get lost or jumbled in the sea anemone for 600 million years – and in the vertebrates, who presumably use the same genetic toolkit as fruit flies and nematodes (e.g., genes for muscles, nerves, senses, reproduction and digestion). Science Daily also used the word “apparently” based on the assumption of common descent: “The anemone genome, on the other hand, has apparently changed less through time and makes a good reference for comparison with human and other vertebrate genomes in order to discover the genes of our common ancestor and how they were organized on chromosomes.” Nevertheless, Eugene Koonin of the National Center for Biotechnology Information in Bethesda, Maryland, was surprised at the complexity of this supposed primitive creature. He told The Scientist that this implies that the common ancestor of all animals “was already extremely highly complex, at least in terms of its genomic organization and regulatory and signal transduction circuits, if not necessarily morphologically.” The article said this pattern contradicts “the widely held belief that organisms become more complex through evolution.” The original paper concluded by attempting to put the genetic surprises into an evolutionary context that would allow for both extreme “tinkering” and extreme stasis. The tension is palpable:Some are the result of domain shuffling, bringing together on the animal stem new combinations of domains that are shared with other eukaryotes. But many animal-specific genes contain sequences with no readily recognizable counterparts outside of animals; these may have arisen by sequence divergence from ancient eukaryotic genes, but the trail is obscured by deep time. Although we can crudely assign the origins of these genes to the eumetazoan stem, this remains somewhat unsatisfying. The forthcoming genomes of sponges, placozoans, and choanoflagellates will allow more precise dating of the origins and diversification of modern eumetazoan gene families, but this will not directly reveal the mechanisms for new gene creation. Presumably, many of these novelties will ultimately be traced back, through deep sequence or structural comparisons, to ancient genes that underwent extreme “tinkering”.They ended by reminding everyone that genes have to do something. Finding that part out, and tracing it back through misty trails of evolutionary ancestry, is easier said than done:The eumetazoan progenitor was more than just a collection of genes. How did these genes function together within the ancestor? Unfortunately, we cannot read from the genome the nature of its gene- and protein-regulatory interactions and networks. This is particularly vexing as it is becoming clear—especially given the apparent universality of the eumetazoan toolkit—that gene regulatory changes can also play a central role in generating novelties, allowing co-option of ancestral genes and network stonew [sic] functions. Of particular interest are the processes that give rise to body axes, germ layers, and differentiated cell types such as nerve and muscle, as well as the mechanisms that maintain these cells and their interactions through the growth and repair of the organism. Nematostella and its genome provide a platform for testing hypotheses about the nature of ancestral eumetazoan pathways and interactions, with the use of the basic principle of evolutionary developmental biology: Processes that are conserved between living species were likely functional in their common ancestor.1Putnam et al, “Sea Anemone Genome Reveals Ancestral Eumetazoan Gene Repertoire and Genomic Organization,” Science, 6 July 2007: Vol. 317. no. 5834, pp. 86-94, DOI: 10.1126/science.1139158.2Elisabeth Pennisi, “Genomics: Sea Anemone Provides a New View of Animal Evolution,” Science, 6 July 2007: Vol. 317. no. 5834, p. 27, DOI: 10.1126/science.317.5834.27.“Extreme tinkering” – you saw it again right there: the evolutionists bowing to Tinker Bell, their goddess of novelty. Now, however, they can’t figure out how she could also be the goddess of conservation. Creation is full of booby traps for those who deny it was purposefully and intelligently designed. Picture a group of blind men walking barefoot through a minefield of mousetraps in the wrong direction. It is a measure of fallen man’s stubbornness when every surprise, no matter how painful, assures them that they are making progress. Each ouch, they confidently claim, is shedding light on their way (whatever “light” means to a blind man). The way is hard for those who walk by pain, not by sight (Proverbs 4:19), especially when light is readily available to all who choose to see (Psalm 119:130, John 1:1-14).(Visited 512 times, 1 visits today)FacebookTwitterPinterestSave分享0
Brittle stars are included within a whole range of species, which contribute to knowledge in the medically important area of tissue regeneration. All brittle stars regenerate lose limbs, but the rate at which this occurs is highly variable and species-specific. One of the slowest rates of arm regeneration reported so far is that of the Antarctic Ophionotus victoriae. Additionally, O. victoriae also has an unusual delay in the onset of regeneration of about 5 months. Both processes are of interest for the areas of regeneration biology and adaptation to cold environments. One method of understanding the details of regeneration events in brittle stars is to characterise the genes involved. In the largest transcriptome study of any ophiuroid to date, we describe the results of mRNA pyrosequencing from pooled samples of regenerating arms of O. victoriae. The sequencing reads resulted in 18,000 assembled contiguous sequences of which 19% were putatively annotated by blast sequence similarity searching. We focus on the identification of major gene families and pathways with potential relevance to the regenerative processes including the Wnt/β-catenin pathway, Hox genes, the SOX gene family and the TGF beta signalling pathways. These data significantly increase the amount of ophiuroid sequences publicly available and provide candidate transcripts for the further investigation of the unusual regenerative process in this Antarctic ophiuroid.