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- March 6, 2009
- 03:25 PM
- 989 views
Complex gene action in a simple organogenesis model
by in Chance and Necessity
The adult hermaphrodite of the roundworm, Caenorhabditis elegans, has only 959 cells, but even with these few cells, the animal has distinct tissues and organs, including muscles, skin, intestine, a nervous system, and an excretory system. The developmental origin of each of the 959 cells is largely invariant and is described by the cell lineage of the animal—the observed pattern of cell divisions from embryogenesis to adulthood. Further, the fate of each of these cells is also largely invar........ Read more »
V RAJAKUMAR, & H CHAMBERLIN. (2007) The Pax2/5/8 gene egl-38 coordinates organogenesis of the C. elegansegg-laying system. Developmental Biology, 301(1), 240-253. DOI: 10.1016/j.ydbio.2006.08.068
- February 23, 2009
- 11:30 PM
- 1,260 views
Geoffroy's lobster and the animal common ancestor
by in Chance and Necessity
In the spring of 1830, a great debate raged in Paris. This debate centered not on the actions of the restored Bourbon monarchy, which would be deposed in late July of that year, but instead on the nature of animal forms. On the one side was Georges Cuvier, who divided animals into four distinct, unbridgeable embranchements with anatomical characteristics exquisitely adapted, by the hand of the Creator, to an organism’s “conditions of existence.” On the other was Etienne Geoffroy Saint-H........ Read more »
E. M. De Robertis, & Yoshiki Sasai. (1996) A common plan for dorsoventral patterning in Bilateria. Nature, 380(6569), 37-40. DOI: 10.1038/380037a0
- January 30, 2009
- 03:30 PM
- 1,102 views
How the fruit fly evolved its (developmental) stripes
by in Chance and Necessity
Patterning the anterior/posterior (head-to-tail) axis of Drosophila melanogaster involves a complicated hierarchy of gene products contributed to the egg by the mother that switch on and off the genes within the zygote that will subdivide the embryo into large sections with different fates from one another. These factors, the gap genes, act in concert with the maternal factors to then regulate a set of genes called pair-rule genes that are expressed in (and will define the fate of) every other ........ Read more »
Michael Z. Ludwig, Casey Bergman, Nipam H. Patel, & Martin Kreitman. (2000) Evidence for stabilizing selection in a eukaryotic enhancer element. Nature, 403(6769), 564-567. DOI: 10.1038/35000615
- January 23, 2009
- 06:25 PM
- 1,143 views
Mitochondria, flies, and Parkinson's disease
by in Chance and Necessity
I’ve previously described a study in which Drosophila melanogaster was used as a genetic model for the mosquito, to identify host genes important for survival and growth of the malaria trypanosome in the mosquito. That’s somewhat atypical, in that the fruit fly is being used as a model for another insect. More typically, model organisms like the fly are used as models for human development and disease. The first paper in my weekly discussions with my developmental biology class fell into ........ Read more »
Ira E. Clark, Mark W. Dodson, Changan Jiang, Joseph H. Cao, Jun R. Huh, Jae Hong Seol, Soon Ji Yoo, Bruce A. Hay, & Ming Guo. (2006) Drosophila pink1 is required for mitochondrial function and interacts genetically with parkin. Nature, 441(7097), 1162-1166. DOI: 10.1038/nature04779
- October 31, 2008
- 06:00 AM
- 1,158 views
Just in time for Halloween--Bats!
by in Chance and Necessity
For Oct. 31 it’s only fitting that we should turn our sights to one of the favorite motifs in Halloween decorations—the bat. Bats are the only mammals capable of powered flight (Rocket J. Squirrel and friends are just gliders), which is made possible by the dramatic alterations to their forelimbs. Most notably, the extremely elongated digits 2-5 act as the scaffold for the expanded interdigital webbing. Understanding the genetic basis of morphological changes like these is a key goal of e........ Read more »
Russell Ray, & Mario Capecchi. (2008) An examination of the Chiropteran HoxD locus from an evolutionary perspective. Evolution , 657-670. DOI: 10.1111/j.1525-142X.2008.00279.x
D. Hockman, C. J. Cretekos, M. K. Mason, R. R. Behringer, D. S. Jacobs, & N. Illing. (2008) A second wave of Sonic hedgehog expression during the development of the bat limb. Proceedings of the National Academy of Sciences. DOI: 10.1073/pnas.0805308105
- October 6, 2008
- 06:30 AM
- 929 views
Using fruit flies to model..the mosquito
by in Chance and Necessity
Model organisms are a common feature of biological research these days. A relatively few organisms, known to practitioners by such informative descriptors as “the” fly and “the” worm, have been used to explore processes in cell and molecular biology, developmental biology, and neurobiology. Yeast (mostly just one--Saccharomyces cerevisiae), zebrafish (Danio rerio), chick (Gallus gallus), mouse (Mus musculus), the frog (Xenopus laevis), and thale cress (Arabidopsis thaliana) round out th........ Read more »
S. M. Brandt, G. Jaramillo-Gutierrez, S. Kumar, C. Barillas-Mury, & D. S. Schneider. (2008) Use of a Drosophila Model to Identify Genes Regulating Plasmodium Growth in the Mosquito. Genetics. DOI: 10.1534/genetics.108.089748
- September 30, 2008
- 02:17 PM
- 1,181 views
Hitchhike for now, parasite later?
by in Chance and Necessity
Parasites can be some of the most streamlined organisms on the planet. By taking advantage of the resources pilfered from their hosts, they may be able to jettison portions of their own metabolic processes—no need to keep those around if the host is doing all the work anyway. For instance, the parasitic nematode Brugia malayi lacks 9 of 10 enzymes required for purine synthesis, 6 of 7 genes required for heme biosynthesis, and all 5 enzymes required for riboflavin biosynthesis (Ghedin et al.,........ Read more »
Christoph Dieterich, Sandra W Clifton, Lisa N Schuster, Asif Chinwalla, Kimberly Delehaunty, Iris Dinkelacker, Lucinda Fulton, Robert Fulton, Jennifer Godfrey, Pat Minx.... (2008) The Pristionchus pacificus genome provides a unique perspective on nematode lifestyle and parasitism. Nature Genetics, 40(10), 1193-1198. DOI: 10.1038/ng.227
- August 5, 2008
- 10:56 PM
- 860 views
Losing segmentation in nervous system development
by in Chance and Necessity
Lots of animals have segments—repeated organizational structures, often along the head-to-tail axis of the animal. Arthropods may represent the most obvious example of this type of organizational scheme, but annelids (e.g., earthworms and leeches) and chordates (e.g. people) are also notable for their segmentation. This type of organization seems to allow a great deal of flexibility, and segments are often subtly (or not so subtly) modified versions of one another (consider the vertebrae in ........ Read more »
A KRISTOF, T WOLLESEN, & A WANNINGER. (2008) Segmental Mode of Neural Patterning in Sipuncula. Current Biology, 18(15), 1129-1132. DOI: 10.1016/j.cub.2008.06.066
- August 4, 2008
- 10:18 PM
- 927 views
Increasing neurogenesis in the adult mammalian brain
by in Chance and Necessity
The conventional wisdom is that we are born with all the brain cells we’re ever going to have, and it’s all downhill from there—as we age, we lose brain cells, never to replace them. This, of course, explains why teenagers are so much smarter than their parents. Unfortunately for the conventional wisdom, it’s wrong. Within the adult central nervous system (CNS) of mammals there are small populations of cells involved in neurogenesis, or the birth of new neurons. A major goal in thera........ Read more »
J-w Jiao, D Feldheim, & D Chen. (2008) Ephrins as negative regulators of adult neurogenesis in diverse regions of the central nervous system. Proceedings of the National Academy of Sciences, 105(25), 8778-8783. DOI: 10.1073/pnas.0708861105
- July 31, 2008
- 07:15 AM
- 874 views
Pigmentation, parallelism, and prediction
by in Chance and Necessity
Proper coloration can be crucial for the survival and reproduction of an organism. Blend into the background, and you might avoid a predator (or be able to sneak up on your prey). Bright plumage can be an important aspect of sexual selection, as it can advertise health and vigor to females choosing mates. Coloration is also a fairly variable trait—many animals have light and dark forms (in addition to subtler gradations in between). Between this variation and its potential for adaptive........ Read more »
Gerli Rosengren Pielberg, Anna Golovko, Elisabeth Sundström, Ino Curik, Johan Lennartsson, Monika H Seltenhammer, Thomas Druml, Matthew Binns, Carolyn Fitzsimmons, Gabriella Lindgren.... (2008) A cis-acting regulatory mutation causes premature hair graying and susceptibility to melanoma in the horse. Nature Genetics, 40(8), 1004-1009. http://www.nature.com/doifinder/10.1038/ng.185
Kelly A McGowan, Jun Z Li, Christopher Y Park, Veronica Beaudry, Holly K Tabor, Amit J Sabnis, Weibin Zhang, Helmut Fuchs, Martin Hrabé de Angelis, Richard M Myers.... (2008) Ribosomal mutations cause p53-mediated dark skin and pleiotropic effects. Nature Genetics, 40(8), 963-970. http://www.nature.com/doifinder/10.1038/ng.188
- July 29, 2008
- 07:27 PM
- 1,247 views
Incorporating evo-devo and the genetics of morphology
by in Chance and Necessity
Scientific controversies typically consist of vigorous exchanges of ideas with periodic injections of new data that may shape the debate. Personalities can certainly influence the path these controversies take, but the ultimate arbiter is data, not drama. In the field of evolutionary developmental biology (evo-devo) we can witness just such a lively situation, both in the literature and at meetings.The general issue the biologists in this debate wish to tackle is the identity of the genes and ........ Read more »
S CARROLL. (2008) Evo-Devo and an Expanding Evolutionary Synthesis: A Genetic Theory of Morphological Evolution. Cell, 134(1), 25-36. http://linkinghub.elsevier.com/retrieve/pii/S0092867408008179
Sean B. Carroll. (2005) Evolution at Two Levels: On Genes and Form. PLoS Biology, 3(7). http://biology.plosjournals.org/perlserv/?request
Hopi E. Hoekstra, & Jerry A. Coyne. (2007) THE LOCUS OF EVOLUTION: EVO DEVO AND THE GENETICS OF ADAPTATION. Evolution, 61(5), 995-1016. http://www.blackwell-synergy.com/doi/abs/10.1111/j.1558-5646.2007.00105.x
S JEONG, M REBEIZ, P ANDOLFATTO, T WERNER, J TRUE, & S CARROLL. (2008) The Evolution of Gene Regulation Underlies a Morphological Difference between Two Drosophila Sister Species. Cell, 132(5), 783-793. http://linkinghub.elsevier.com/retrieve/pii/S0092867408001141
- July 23, 2008
- 07:06 AM
- 1,503 views
Butterfly anti-aphrodisiacs help Brussels sprouts avoid being eaten
by in Chance and Necessity
Kids all across the United States turn up their noses and push their plates away when Brussels sprouts are placed in front of them. But to a caterpillar, Brussels sprouts are good eating. So much so that Brussels sprouts plants need to defend themselves. Plant defense options are somewhat limited—grow someplace it’s difficult for the herbivore to reach; release chemicals that repel herbivores; make the plant itself difficult to eat (e.g., thorns); or accumulate chemical toxins tha........ Read more »
N Fatouros, C Broekgaarden, G Bukovinszkine'Kiss, J J van Loon, R Mumm, M E Huigens, M Dicke, & M Hilker. (2008) From the Cover: Male-derived butterfly anti-aphrodisiac mediates induced indirect plant defense. Proceedings of the National Academy of Sciences, 105(29), 10033-10038. DOI: 10.1073/pnas.0707809105
- July 10, 2008
- 07:09 PM
- 776 views
Defining segments, guiding neurons
by in Chance and Necessity
Individual neurons in the sciatic nerve can have axons that traverse the entire length, a meter or so, of the leg. Some of the mechanisms that these cell extensions use to navigate on their journey outward from the cell body to their eventual target have been pieced together from genetic and molecular studies in model organisms like the worm, the fly, the chick, and the mouse.Two of the most important molecules identified in this process are the signaling molecule Slit and its receptor Robo. T........ Read more »
Marc Geisen, Thomas Di Meglio, Massimo Pasqualetti, Sebastien Ducret, Jean-François Brunet, Alain Chedotal, Filippo M Rijli, & Huda Y Zoghbi. (2008) Hox Paralog Group 2 Genes Control the Migration of Mouse Pontine Neurons through Slit-Robo Signaling. PLoS Biology, 6(6). DOI: 10.1371/journal.pbio.0060142
- June 19, 2008
- 09:14 AM
- 1,414 views
Of snakes and somites
by in Chance and Necessity
Snakes get a bad rap—they are the bad guys in the Garden of Eden, Kipling’s “Rikki-Tikki-Tavi, and of course, Snakes on a Plane. Despite these villainous turns, they are of tremendous interest to morphologists and developmental biologists because of their highly derived axial anatomy. The most obvious feature is the loss of limbs, but just as curious is their highly elongated vertebral column. Whereas your average fish has ~48 vertebrae, your typical bird somewhere between 3........ Read more »
Céline Gomez, Ertuğrul Özbudak, Joshua Wunderlich, Diana Baumann, Julian Lewis, & Olivier Pourquié. (2008) Control of segment number in vertebrate embryos. Nature. DOI: 10.1038/nature07020
- June 16, 2008
- 10:13 AM
- 716 views
Rational redesign of bacterial signaling proteins based on amino acid co-evolution
by in Chance and Necessity
Whether independent and unicellular or nestled within multicellular organisms, cells must have the ability to respond to their environment in an appropriate fashion. Responding to physical and chemical aspects of the environment is crucial, but so is responding to neighboring cells that also inhabit that environment. In multicellular animals a surprisingly small set of molecules coordinate the complex communication between cells to direct important cellular processes, such as cell growth, divi........ Read more »
J SKERKER, B PERCHUK, A SIRYAPORN, E LUBIN, O ASHENBERG, M GOULIAN, & M LAUB. (2008) Rewiring the Specificity of Two-Component Signal Transduction Systems. Cell, 133(6), 1043-1054. DOI: 10.1016/j.cell.2008.04.040
- June 4, 2008
- 08:10 PM
- 812 views
Flexible grammar in regulatory switches
by in Chance and Necessity
More than 30 years ago, Alan Wilson and Mary Claire-King suggested that the proteins of chimpanzees and humans were not sufficiently different to account for the dramatic differences in behavior and appearance in the two groups. Instead, they proposed that differences in how those proteins were deployed might better explain the distinct characteristics of chimps and humans.Now that both the human and chimpanzee genomes have been sequenced, the genes (and the proteins they encode) appear to tell........ Read more »
S RASTEGAR, I HESS, T DICKMEIS, J NICOD, R ERTZER, Y HADZHIEV, W THIES, G SCHERER, & U STRAHLE. (2008) The words of the regulatory code are arranged in a variable manner in highly conserved enhancers. Developmental Biology, 318(2), 366-377. DOI: 10.1016/j.ydbio.2008.03.034
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