It may appear difficult to reconcile the fact that almost every cell in the body of an animal has an identical dose of genes with the variety of different appearances and properties cells can display—bone, skin, hair, muscle, and many more. This may seem even more complex given that all of these tissue types derive originally from a single fertilized egg cell. Understanding the many regulatory mechanisms that create different cells from a single template is the work of developmental biology. A new paper published this week in the open-access journal PLoS Biology looks at this problem in the olfactory system of the fruit fly, where the ability to discriminate odors depends on receptor cells expressing different patterns of receptor genes, despite each cell having the same set of genes to choose from. The paper, by Anandasankar Ray and colleagues at Yale University, shows that receptor patterns are controlled by DNA sequences upstream of the receptor genes.
In the fruit fly Drosophila, there are two organs involved in smell: the antennae and the maxillary palps—the latter being part of the mouth. In these palps, there are always six types of neurons, cells that transmit information from the sensing part to the brain. Each type of neuron has a different, predictable pattern of olfactory receptors. How a neuron knows which receptors to express was, until now, a mystery.
By comparing the recently published genetic sequences of 12 species of Drosophila, Ray and colleagues identified regions of DNA near the receptor genes that are almost identical in all species. They hypothesized that these represented control regions, which are important for determining how genes are expressed. By altering the control regions experimentally, they have shown that this is true; these highly conserved regions act like zip codes, determining where the receptors end up. Interestingly, some regions positively regulate gene expression: when they are damaged, the receptor fails to be expressed in neurons where it would normally appear. Other regions negatively regulate receptor expression (stopping receptors from appearing in the wrong neurons) so that when the regulator is experimentally blocked, the related receptor appears in more neurons than it should.
Interestingly, the regulatory sequences identified in this study may also have another role in the nervous system. These controlling elements might also be apparent in the process of axon guidance, which connects the olfactory neurons to neurons in the antennae. This complex connection suggests that the process goes beyond the expression of olfactory neurons, and also contributes to the design and development of the fruit fly’s greater nervous system.
###
"_blank">Citation: Ray A, van der Goes van Naters W, Carlson JR (2008) A regulatory code for neuron-specific odor receptor expression. PLoS Biol 6(5): e125. doi:10.1371/journal.pbio.0060125
Public Library of Science: http://www.plos.org/ Article found using EurekAlert!, a service of AAAS.
This article has been viewed 702 time(s).
 |
 Digg |
 FarkIt |
 |
 StumbleUpon |
 del.icio.us |
 |
In 1824, three years before he began to publish his famous "double elephant folio" The Birds of America, John James Audubon (1785-1851), the eminent artist of American birds and animals, created a drawing of a running grouse for use in the design for a New Jersey bank note.
The recent discovery of more than a thousand genes known as large intergenic non-coding RNAs (or "lincRNAs") opened up a new approach to understanding the function and organization of the genome. That surprising breakthrough is now made even more compelling with the finding that dozens of these lincRNAs are induced by p53, the most commonly mutated gene in cancer
A genetics research team based at The Children's Hospital of Philadelphia continues to discover recurrent translocations—places in which two chromosomes exchange pieces of themselves. As many as 1 in 600 persons carry balanced chromosome translocations, which involve no loss or gain of DNA.
Some trees growing in nutrient-poor forest soil may get what they need by cultivating specific root microbes to create compounds they require. These microbes are exceptionally efficient at turning inorganic minerals into nutrients that the trees can use. Researchers from France report their findings in the July 2010 issue of the journal Applied and Environmental Microbiology.
"Macho, macho man. I've got to be, a macho man. Macho, macho man. I've got to be a macho!" — The Village People
"If one finds something once, it's accidental. If it is found twice, it's puzzling. If found thrice, there is a pattern," the archaeologists Olle Hemdorff and Eva Thäte say.
"In laboratory tests, right- and left-handers associate positive ideas like honesty and intelligence with their dominant side of space and negative ideas with their non-dominant side," says Daniel Casasanto of the Max Planck Institute for Psycholinguistics in Nijmegen, Netherlands.
Often causing no symptoms in carriers of the disease, worldwide tuberculosis (TB) infects eight to ten million people every year, kills two million, and it is highly contagious as it is spread through coughing and sneezing.