Nature Biotechnology pp 353 - 358 and pp 346 - 347

Using fiber optic bundles, scientists at University of California (San Diego) and Illumina (Boston, MA) have developed a sensitive method for tracking "alternative splicing," a trick used by cells to produce more than one protein from the same gene. The method should be useful for understanding the role of alternative splicing in human development and disease, and for solving a major puzzle of the recently sequenced human genome-the surprisingly small number of human genes.

Human cells make the most of the genes they inherit by cutting and pasting RNA gene transcripts in different ways, generating multiple proteins from a single gene. In theory, one could identify all the alternatively spliced RNAs in a cell sample simply by sequencing them, but this is still a slow, laborious process.

Instead, Xiang-Dong Fu and his colleagues decided to look only at the regions of RNA (splice junctions) where splicing enzymes do their cutting. By determining how much of each splice junction is present in a particular sample, they hoped to reconstruct a global picture of alternative splicing in those cells.

The method is based on short, synthetic DNA molecules, called "oligos", that are complementary to the sequences on both sides of all possible splice junctions in the sample. The oligos bind to any splice junctions that are present and are then joined together by an enzyme, creating a longer oligo that is like a fingerprint of that particular splice junction. Finally, the amounts of each oligo fingerprint are measured on a fiber optic microarray.

Fu and his colleagues showed that the method is sensitive, allowing detection of alternatively spliced RNAs from less than 10 cells, and that it could be used to analyze the splice products of nearly 100 genes simultaneously.

Nature Biotechnology pp 366 - 369

In the April issue of Nature Biotechnology, Jean-Paul Renard and his colleagues report the successful cloning of rabbits from adult cells. While cloning might seem rather redundant in view of the bunny's ability to reproduce by natural methods, the possibility of targeting specific genes in nuclear DNA during the cloning process could markedly enhance the use of rabbits as models of human disease.

Renard and his team started out by adapting established methods for cloning other animals. They first removed the nucleus from a female's egg at a precisely timed stage and then electrically fused it with an adult cell from a donor rabbit, which provides the nuclear material to be cloned. Renard and coworkers succeeded in cloning rabbits where others failed because they minimized the time that the fused cells were in the presence of various chemical agents which, while necessary for the cells to start developing, affects later stages of embryo development. In addition, the researchers identified an exact time window necessary for implantation of the embryo into foster rabbits for full-term growth. The resultant cloned offspring showed normal growth and fertility. Rabbit models of human disease are especially attractive because their physiology more closely resembles humans than laboratory mice or rats.

Nature Biotechnology pp 396 - 399

How would you like your drugs, sir—boiled, fried, or scrambled? In the April issue of Nature Biotechnology, researchers describe chickens genetically engineered to produce an active foreign enzyme in their eggs-the first real evidence that it is feasible to use transgenic chickens to mass produce foreign proteins and biopharmaceuticals. A team of researchers led by Alex Harvey inserted a bacterial gene encoding an enzyme into White Leghorn chicken embryos, which after maturing laid eggs containing the enzyme. The levels of the protein in fresh eggs remained constant for months and across successive generations, and the researchers plan to develop more robust methods of introducing foreign DNA into chickens to increase the amount of protein made. Based on the results with the test protein, a single hen that lays up to 330 eggs per year could produce 17 milligrams or more of a protein drug-enough for variable doses depending on the therapeutic. As many drugs are potent, just one egg could yield multiple doses. Unlike other transgenic animals that take years to produce foreign proteins in milk, chickens can start laying transgenic eggs about 21 weeks after hatching. What's more, the foreign proteins should be much easier to harvest/purify.