Monday, December 24, 2007
Snakes Venom
Biology / Biochemistry News
Article Date: 22 Dec 2007
Venoms from different snake families may have many deadly ingredients in common, more than was previously thought. A study published in the online open access journal BMC Molecular Biology has unexpectedly discovered three-finger toxins in a subspecies of the Massasauga Rattlesnake, as well as evidence for a novel toxin genes resulting from gene fusion. Susanta Pahari from National University of Singapore, Singapore (currently working at Sri Bhagawan Mahaveer Jain College, Bangalore, India) used venom glands from a rare rattlesnake that lives in arid and desert grasslands. Known as Desert Massasauga (Sistrurus catenatus edwardsii), this pitviper is a subspecies of the North American Massasauga Rattlesnake (Sistrurus catenatus).
Together with Stephen Mackessy from the University of Northern Colorado, USA and R. Manjunatha Kini from National University of Singapore, Singapore, Pahari constructed a cDNA library of the snake's venom gland and created 576 tagged sequences. A cocktail of recognized venom toxin sequences was detected in the library, but the venom also contained three-finger toxin-like transcripts, a family of poisons thought only to occur in another family of snakes (Elapidae). The team also spotted a novel toxin-like transcript generated by the fusion of two individual toxin genes, a mechanism not previously observed in toxin evolution. Toxin diversity is usually the result of gene duplication and subsequently neofunctionalization is achieved through several point mutations (called accelerated evolution) on the surface of the protein. Pahari says "In addition to gene duplication, exon shuffling or transcriptional splicing may also contribute to generating the diversity of toxins and toxin isoforms observed among snake venoms." Previously, researchers identified venom compounds using protein chemistry or individual gene cloning methods. However, less abundant toxins were often missed.
The library method has now revealed new toxin genes and even new families of toxins. Taking low abundance toxins into consideration shows advanced snakes' venoms actually have a greater similarity than previously recognized. Snake venoms are complex mixtures of pharmacologically active proteins and peptides. Treating snake venom victims can be complicated because of the variation between venoms even within snake families. Kini says "Such a diversity of toxins provides a gold mine of bioactive polypeptides, which could aid the development of novel therapeutic agents." Read more...
Saturday, December 1, 2007
Is it true?
By Ben Hirschler Fri Nov 30, 3:28 PM ET
LONDON (Reuters) - Genetic tests to assess disease risk are proliferating but many are a waste of money and tell people little more than they would know from studying family history, medical experts said on Friday.
A host of companies now offer tests, typically costing hundreds of dollars, to calculate genetic risks for common conditions like cancer, diabetes and heart disease that involve multiple genes.
But Christine Patch, a genetic counselor at Guy's and St Thomas' NHS Foundation Trust and a member of Britain's Human Genetics Commission, said most had little clinical relevance.
"My message is you are wasting your money," she told a news briefing.
People also faced either unnecessary anxiety, if a test showed a raised risk, or false reassurance, if they were given an all-clear, she added.
Paul Pharoah, from the Cancer Research UK department of oncology at Cambridge University, said real strides were being made in science but researchers still did not know enough about enough genes for tests to be really useful.
Scientists have linked a growing number of genes to common diseases but these genes typically interact in a complicated fashion and their ultimate effect is influenced by environmental factors in ways that are poorly understood.
GENOME-WIDE SEARCH
The field of genetic testing has traditionally involved looking at a few specific genes.
But that is changing with the launch of new genome-wide searches that promise a brave new world of targeted healthcare, in which each individual can see his or her genetic code.
Two companies, Iceland's Decode Genetics Inc and 23andMe, a U.S. firm funded by Google Inc, launched rival services earlier this month offering people a glimpse of their entire genome for just under $1,000.
A third unlisted U.S. company, Navigenics, is set to join the fray shortly.
Stuart Hogarth of the Institute for Science and Society at University of Nottingham said the entry of these new players, with substantial financial backing, highlighted the growing commercialization of the gene testing business.
The risk, however, was that business development plans were running ahead of science, while regulators were left floundering with an inadequate system of oversight.
"We still do not have a regulatory framework that can control this burgeoning field," Hogarth said.
"In the absence of such a regulatory system, we are in severe danger of losing public confidence in what is a very promising and very exciting field of science."
The field of genetic testing has been revolutionized not only by scientific breakthroughs but also by the development of smart chips from the likes of Affymetrix Inc and Illumina Inc, which can test DNA at various sites along a person's genome.
(Reporting by Ben Hirschler; Editing by Rory Channing)
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