11-09-2006, 06:28 PM
Sea urchin gene map filled with surprises
WASHINGTON (Reuters) - Sea urchins may be blind, but they have the same genes that help people see, as well as genes for a sense of smell and one of the most complicated immune systems in the animal world, researchers reported on Thursday.
They also have genes associated with diseases such as Huntington's and muscular dystrophy, offering new routes to understanding illnesses, the researchers write in Friday's issue of the journal Science.
The sea urchin -- a pincushion-shaped animal found at the bottom of the sea and perhaps best known for its long, sharp spines -- shares more than 7,000 genes with humans, the international team of researchers found.
WOW, it's hard to believe that a creature like that shares over 7,000
genes with us.
for more: http://news.yahoo.com/s/nm/20061109/sc_nm/science_urchin_dc
11-11-2006, 01:43 AM
This is very interesting indeed, that the sea urchin contains all these genes for vision and neurons (Huntington's). Either sea urchins descended from animals that had features that these genes coded for or, more likely, the genes are used for many other things besides vision and neurons, or at least vision and neurons as we know them.
Can animals evolve to lose their sight? When I was a graduate student, I studied an blind owl that lived in caves of Colombia (South America). These owls are really amazing. They fly around using only echo-location and catch bats for their meals. Their cerebellums contain an extra-large seventh lobule, which bats, whales, and other echo-locating mammals share. They are blind (as bats...) and their loss of eye-sight may have occurred over many years, just as cave-fishes are blind, presumably because they no longer need their visions. However, they still have eyes and some of the apparati associated with eyes.
A Sunday Tribune article of India (Source (http://www.tribuneindia.com/2000/20001015/spectrum/nature.htm)) discusses cave crickets, ear-wings, centipedes, and spiders that live in caves. These animals still have their "eyes" but have evolved organs and changes in the brains that greatly expand their "touch" senses. Many animals have evolved amazing touch senses, including birds that can use their beaks to find food in mud. Blind people also have finely developed touch senses, including the ability to change their brains read braille. Recent studies suggest that the ability to read braille utilizes the visual cortex, suggesting tha the brain is really a general purpose computer that can adapt within weeks to utilize its circuits for sensory input as diverse as visual and touch sensation.
When I was on the Council of the National Institute of Child Health and Disorders (NICHD) from 2000-2005, the Institute decided to invest in genomic analyses of various model animal systems, including the roundworm C. Elegans, the African clawed toad, Zebrafish and other animals. This has turned out to be a treasure of information. The C. Elegans genome is of particular interest because they apparently had many of the guidance molecules for brain development, including both the ligand and receptors for Netrin, the first soluble neural growth guidance molecule that is largely responsible for the development of decussated (crossed) spinal tracts.
These so-called "primitive" animals are not as primitive as we think. They evolved mechanisms that we mammals adapted for other purposes, that allowed us to develop the brains that we have. For example, although many primitive animals don't have myelinated axons, they possess many of the genes that Schwann cells use to myelinate axons. Other examples include the cell adhesion molecule L1 and the structure of the antibody molecule. The L1 molecule has components of the antibody molecule, called Ig modules. It makes sense when we think about it, that cells in living organisms need o be able to recognize each other and to respond in ways that allow them to develop.
Studies of gene regulatory mechanisms of the sea urchin has provided significant insights into transcriptional factors that shut down, balance, or stabilize gene expression (Source (http://icb.oxfordjournals.org/cgi/content/abstract/46/3/233)). In the same way that studies of the common bacteria E. coli gave us our first clues of how gene expression is regulated by promoter genes. I still remember the time when all the we knew about promoters, negative gene expression feedback, translation, transcription, and protein synthesis came from bacteria. That was not so long ago, in the 1970's. We assumed that these were the same mechanisms that mammals used. This assumption has been confirmed over and over again, strongly supporting the concept of evolution.
The fact that sea urchins genetics is important is reinforced by the number of papers that cited a recent study of sea urchine gene analysis (Source (http://www.sciencemag.org/cgi/content/abstract/279/5358/1896?ijkey=7bf84a3d893536959ee9cc3a3c9193208362b8d b)). The web page containing the abstract of the article lists about 50 papers that cited that article. These include titles as diverse as genetic control of muscle, myelination, olfactory and chemosensory genes, liver development, and many other subjects that one would not have thought would have anything to do with sea urchins. This is one of the best justifications of "basic science" that I know of. The amazing interconnections between species has taught us a great deal.