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Gene expression in alligators suggests birds have 'thumbs'
October 06, 2008The latest breakthrough in a 120 year-old debate on the evolution of the bird wing was published in the open-access journal PLoS ONE, October 3, by Alexander Vargas and colleagues at Yale University, the University of Wisconsin-Madison and Yale Peabody Museum of Natural History.
Bird wings only have three fingers, having evolved from remote ancestors that, like humans and most reptiles, had five fingers. Biologists have typically used embryology to identify the evolutionary origin (homology) of structures; the three fingers of the bird wing develop from cartilage condensations that are found in the same positions in the embryo as fingers two, three and four of humans (the index, middle and ring fingers). However, the morphology of the fingers of early birds such as Archaeopteryx corresponds to that of fingers one, two and three in other reptiles (thumb, index and middle finger). The fossil record clearly shows that fingers four and five (ring and pinky finger) were lost and reduced in the dinosaur ancestors of birds.
Further, the lack of expression of the HoxD-11 gene in the first finger of the wing makes it most similar to finger one (the "thumb") of the mouse, consistent with comparative morphology. However, the mouse is only distantly related to birds; crocodilians, in turn, are bird's closest living relatives.
To see whether the evidence from mouse HoxD-11 expression held up, Vargas and colleagues, working at the lab of Gunter Wagner at Yale, have examined the expression of this gene in alligators; they found the expression to be, as in mice, absent only in finger one (the "thumb").
Developmental and evolutionary biologists are familiar with the phenomenon of homeotic transformations, in which one structure begins to develop at a different position within the body. A famous example is the case of the fruitfly mutant antennapaedia, which develops legs on its head instead of antennae. The new work by Vargas et al. rekindles the hypothesis that a "hometic frameshift" occurred in the evolution of the bird wing, such that fingers one, two and three began to develop from the embryological positions of fingers two, three and four.
Public Library of Science
To see whether the evidence from mouse HoxD-11 expression held up, Vargas and colleagues, working at the lab of Gunter Wagner at Yale, have examined the expression of this gene in alligators; they found the expression to be, as in mice, absent only in finger one (the "thumb").
Developmental and evolutionary biologists are familiar with the phenomenon of homeotic transformations, in which one structure begins to develop at a different position within the body. A famous example is the case of the fruitfly mutant antennapaedia, which develops legs on its head instead of antennae. The new work by Vargas et al. rekindles the hypothesis that a "hometic frameshift" occurred in the evolution of the bird wing, such that fingers one, two and three began to develop from the embryological positions of fingers two, three and four.
Public Library of Science
Gene Expression Current Events and Gene Expression News RSSNew research into the mechanisms of gene regulation
A team led by Penn State's Ross Hardison, T. Ming Chu Professor of Biochemistry and Molecular Biology, has taken a large step toward unraveling how regulatory proteins control the production of gene products during development and growth.
The Protein Srebp2 Drives Cholesterol Formation in Prion-Infected Neuronal Cells Which May Promote Prion-Dependent Diseases
The regulating protein Srebp2 drives cholesterol formation, which prions need for their propagation, in prion-infected neuronal cells.
Study reveals why certain drug combinations backfire
Combination drug therapy has become a staple for treating many infections. For instance, doctors treat extensively drug resistant forms of tuberculosis with one drug that breaks down the pathogen's protective barriers and opens the door for another to deliver the deathblow.
Penn Study Provides First Clear Idea of How Rare Bone Disease Progresses
An international team of scientists, led by researchers at the University of Pennsylvania School of Medicine, is taking the first step in developing a treatment for a rare genetic disorder called fibrodysplasia ossificans progressiva (FOP), in which the body's skeletal muscles and soft connective tissue turns to bone, immobilizing patients over a lifetime with a second skeleton.
Why can't chimps speak?
If humans are genetically related to chimps, why did our brains develop the innate ability for language and speech while theirs did not?
Treatment to improve degenerating muscle gains strength
A study appearing in Science Translational Medicine puts scientists one step closer to clinical trials to test a gene delivery strategy to improve muscle mass and function in patients with certain degenerative muscle disorders.
BUSM researchers show dieters can experience neurobiological similarities of drug addicts
Researchers from Boston University School of Medicine (BUSM) have shown that intermittent access to foods rich in fat and sugar induces changes in the brain which are comparable to those observed in drug dependence.
FDA approved leukemia drugs shows promise in ovarian cancer cells
The drug Sprycel, approved for use by the U.S. Food and Drug Administration in patients with chronic myeloid leukemia, significantly inhibited the growth and invasiveness of ovarian cancer cells and also promoted their death, a study by researchers with UCLA's Jonsson Comprehensive Cancer Center found.
Deciphering the regulatory code
Embryonic development is like a well-organised building project, with the embryo's DNA serving as the blueprint from which all construction details are derived.
Experimental agent reduces breast cancer metastasis to bone
Researchers have reduced breast cancer metastasis to bone using an experimental agent to inhibit ROCK, a protein that was found to be over-expressed in metastatic breast cancer.
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