It once took several months, even years, to identify the role of a particular gene. Thanks to a breakthrough from researchers at the University of Utah in Salt Lake City, those months have been reduced to days. By removing transposons from Drosophila and then inserting and activating them in Caenorhabditis elegans, the group developed a new technique that will speed up gene identification (J.L. Bessereau et al., "Mobilization of a Drosophila transposon in the Caenorhabditis elegans germ line," Nature, 413:70-8 Sept. 6, 2001.) A transposon, or "jumping gene" is a snippet of DNA that, when excised from its regular chromosomal location and activated by a transposase to help insertion, can randomly integrate itself elsewhere within the genome and mutate or "disrupt" another gene. Jumping genes that are tagged allow for the immediate identification of a mutant gene. Researchers used Mos1 because it doesn't require any additional factors for transposition and can be transposed in heterologous species. Utah biologist M. Wayne Davis says C. Elegans is a widely used species in genetics because members of the species "reproduce in heaps and grow quickly. They are also self-fertilizing hermaphrodites, so exact copies can be made without a cross-breed." Transposons can jump almost anywhere within the genome, giving progeny a wide range of morphologies from which it can be inferred what genes have been mutated. Before this new technique, genetic mapping involved point mutations, where locating a single mutation was exceedingly tedious. In a prepared statement, associate professor of biology Erik Jorgenson said the group developed the technique to create a faster way to find genes involved in the transmission of nerve signals.
Drawing Out the Memory Chain with Leeches
How humans transfer short-term memory into long-term memory is a hot topic in neurology. The recent discovery of CREB (cyclic AMP response element binding protein) in the medicinal leech Hirudo medicinalis, might help shed some light. CREB, known to have importance in human memory, was found in the leech central nervous system by researchers from Harvey Mudd College in Claremont, Calif. (J. Groome, et al., "Distribution and partial characterization of CREB-like immunoreactivity in the medicinal leech Hirudo," Invertebrate Neuroscience, [In Press]). Researchers used the leech because of its simple nervous system and ability to exhibit learned and adaptive behavior. Each leech has 32 segments, each with a brain containing about 400 neurons. "One thing that's attractive about using leeches is that each brain has such a small number of neurons and ... [they] are easily accessible. This enables us to identify all of them," says Jim Groome, assistant professor of biology at Harvey Mudd College. "We can record the activity of each neuron and determine what hormones and neurotransmitters they're dealing with." Groome's team discovered CREB in the leeches when antibodies that bind to CREB in rabbits were introduced into the leech and found the antibody bound in the leech's protein as well. CREB can bind to DNA and change gene expression; by having this protein in a simpler organism, Groome hopes to find out exactly how the protein functions in the leech's rudimentary nervous system, and eventually in humans.
