Eating for Two, or an Entire Lineage; Serine at the Start of Life; Interdisciplinary Research
Eating for Two, or an Entire Lineage
Courtesy of Randy Jirtle
Duke University researchers give a new twist to the old adage, "You are what you eat." By feeding female agouti (Avy) mice methyl-rich supplements such as folic acid and vitamin B12, Randy Jirtle and Robert Waterland reduced agouti gene expression in their offspring. This change, caused by direct methylation of a transposon at the 5' end of the agouti locus, resulted in dramatic, visible changes in pups, including darkened coat color and decreased weight gain.1 "Transposons are genomic parasites," says Jirtle, explaining that epigenetic mechanisms such as methylation have evolved to counteract transposon-initiated gene expression.
The research has broad implications. Such epigenetic effects could muddle sequence-driven disease gene hunts; the fact that environmental factors can cause potentially heritable genetic changes blurs the boundaries between nature and nurture. "It's definitely Lamarckian," says Jirtle, referring to the largely discredited 19th century evolutionist who proposed the inheritance of acquired traits.
Ted Steele, Australian researcher and author of Lamarck's Signature, lauds the work's contribution. "It is clear, phenotypic diversity influenced by a direct environmental trigger, in this case food," he says. Arthur Beaudet, Baylor College of Medicine in Houston, says the work will change the way people think about dietary supplements. Jirtle adds, "Trivial doses can dramatically affect gene expression."
Serine at the Start of Life
Adapted from Z. Takats et al.
Clusters of the amino acid serine may have lent a hand during life's origins. Many biomolecules, such as DNA, carbohydrates, and amino acids, have right- or left-handed conformations. Chemists struggle to control handedness, or chirality, in the lab, but nature generally uses only left-handed (L) amino acids and right-handed (D) sugars.
Purdue University's Graham Cooks says serine may have dictated this preference. Unlike other amino acids, serine forms stable clusters exclusively from D or L forms that can interact with other amino acids. Now, he has found that serine forms stable clusters with biological molecules such as glyceraldehydes and phosphoric acid, and metals such as copper and iron, ingredients likely to have been present at the start of life.
If prevalent, left-handed serine clusters would have influenced many other reactions. "Once left-handed clusters had been selected for, this would have led to L-amino acids and D-sugars accumulating," says Cooks, tipping life towards its present handedness.1 "Cooks' experiments could be of utmost importance in explaining how handedness was propagated, even if they do not explain its origin," says Christoph Schalley of Bonn University.
Yet, while the result is very interesting, says Glasgow University's Laurence Barron, "It's just one of a plethora of plausible starting points for the origin of prebiotic biomolecular handedness, any one (or none) of which might have had something to do with it."
These papers were selected from multiple disciplines from the Faculty of 1000, a Web-based literary awareness tool (www.facultyof1000.com).
D.C. Presgraves et al., "Adaptive evolution drives divergence of a hybrid inviability gene between two species of Drosophila," Nature, 12:715-9, June 12, 2003.
"The 'holy grail' of genetic studies of speciation has been to identify the actual genes involved and the evolutionary forces that shaped their histories ... [The authors] elegantly map a hybrid inviability factor to the gene Nup96, and then confirm its role in male hybrid inviability ... Further, they show the signature of natural selection having acted on the divergence of this gene between Drosophila melanogaster and [Drosophila] simulans."
--Mohamed Noor, Louisiana State University
P. Cliften et al., "Finding functional features in Saccharomyces genomes by phylogenetic footprinting," Science, 301:71-6, July 4, 2003.
"[These investigators] introduce a powerful bioinformatics method for the genome-wide identification of cis-acting regulatory elements [in] the well-studied yeast genus Saccharomyces ... [They] identify both known and candidate promoter/regulatory elements due to their strong phylogenetic conservation ... and they significantly refine the existing catalog of protein-coding genes in the yeast genome."
--David Brow, University of Wisconsin Medical School
C.C. Huang et al., "Laminin alpha subunits and their role in C. elegans development," Development, 130:3343-58, July 15, 2003.
"A very rich, resource-full paper that describes features of basement membranes in [Caenorhabditis] elegans, both in terms of general anatomy as well as genetic composition. Furthermore, the paper describes and summarizes the function of several extracellular matrix components."
--Oliver Hobert, Columbia University College of Physicians and Surgeons