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Contents Pivotal pump Leptin limbo Clue to obesity Biotech Web site Helping hand Mapping malaria UCSD - Salk Program in Molecular Medicine HEART FAILURE RESCUE: A cross section of a mouse genetically engineered to develop heart failure (left) shows enlarged heart chambers and thin walls that are typical of the condition. A cross section from the same strain of mouse, but with the phospholamban gene (PLB) also missing, appears normal. PIVOTAL PUMP A biochemical calcium pump and the gene that controls it are "pivotal" to the failure of a mechanical one, the heart, reports Kenneth R. Chien, University of California at San Diego molecular geneticist, and colleagues (S. Minimisawa et al., "Chronic phospholamban-sarcoplasmic reticulum calcium ATPase interaction is the critical calcium cycling defect in dilated cardiomyopathy," Cell, 99:531-41, Oct. 29, 1999). Chien and colleagues arrested heart failure in mice by using a gene knockout of phospholamban (PLB), the genetic brake on the heart's calcium pump. Calcium causes the heart to contract. Chien comments that scientists knew for some time that the calcium pump was "down" during heart failure. However, they did not know if the decreased pump activity was driving the disease progression. They also did not know the disease pathway. Through a series of knockout and double knockout experiments, Chien thinks he and colleagues have found at least one such pathway--phosphorylation of PLB. "I don't think it's the only gene or the only pathway," he explains. "But I do think it's critical." That pathway may be a good target for antiheart failure drugs, he concludes. --Paul Smaglik LEPTIN LIMBO Mixed results from a six-month clinical trial of recombinant leptin to induce weight loss have left biopharmaceutical company Amgen uncertain about the protein hormone's therapeutic potential for obesity (S.B. Heymsfield et al., "Recombinant leptin for weight loss in obese and lean adults," JAMA: The Journal of the American Medical Association, 282:1568-75, Oct. 27, 1999). "I think it's a little premature to comment on the potential," says senior author Mark McCamish, clinical research scientist at the Thousand Oaks, Calif.-based company. "The JAMA article suggests there is a biologic effect. That's well and good, because many scientists have had concerns that exogenous leptin wouldn't work." Leptin levels rise in accordance with higher body mass. Therefore, many obese patients who have higher than normal serum leptin concentrations appear to be resistant to the hormone's role in curbing food consumption by signaling the size of the fatty tissue mass. The debate is whether leptin infusions can overcome this resistance. A dose-response relationship with weight loss was observed in the trial, but 26 of 73 obese subjects dropped out, some experiencing injection site reactions. Of eight who finished at the highest dose, two lost substantial weight, five lost weight moderately, and one gained substantially. It is still unknown whether subpopulations of patients who will respond to the treatment can be predicted. "Leptin probably will not be a panacea," McCamish acknowledges. "We're looking at agents that will expand the armamentarium." Amgen is now working with another second-generation leptin molecule.--Steve Bunk CLUE TO OBESITY When "civilization" comes to native peoples, they often develop "advances" such as obesity and diabetes. This fate may await the Inuit, or Canadian Eskimos. A team from the University of Western Ontario, the University of Manitoba, and the University of Toronto has identified a gene predisposing to obesity among the Inuit (R.A. Hegele, "G-protein beta 3 subunit gene splice variant and body fat distribution in Nunavut Inuit," Genome Research, 9: 972-7, October 1999). "Other Canadian aboriginal people who live farther south have had a massive change in their diet and level of activity since adopting the reservation system over the last 30 to 40 years. There has been a notable increase in body mass due to a decrease in their level of activity and an increase in the consumption of energy-dense processed foods," explains Robert Hegele, a staff scientist at the Robarts Research Institute at the University of Western Ontario. So far, the Inuit have escaped this fate thanks to their remote home in the Northwest Territories, but that may change. "Comforts such as insulated homes and store-bought foods, which would have been foreign to their ancestors, are becoming more prevalent," Hegele adds. His team genotyped 213 healthy Inuit for a G-protein gene variant that is part of a signal transduction pathway that packs fat cells. A mutation overdoes it, rounding out the physique. Hegele's team found that Inuit with the mutation have the highest weight, waist, and hip measurements, and skinfold thicknesses. Earlier work had linked the mutation to obesity in another Canadian aboriginal group, the Oji-Cree. The researchers suggest that the gene variant might be used as a marker to detect individuals at high risk of becoming obese from burgeoning dietary choices. --Ricki Lewis BIOTECH WEB SITE The U.S. Department of Agriculture (USDA) has a new Internet site devoted to biotechnology: www.aphis.usda.gov/biotechnology. Run through the Animal and Plant Health Inspection Service (APHIS), the site provides information on the introduction, regulation, safety, and uses of genetically modified crops and transgenic animals, with links to the Food and Drug Administration and Environmental Protection Agency. Web surfers can also access research reports, including the Economic Research Service's recent study of transgenic crop use by America's farmers. "By creating this new central Web site, we're providing a starting point for the general public, media, industry, academia, and our international trading partners to access information about USDA's role in agricultural biotechnology," comments USDA Secretary Dan Glickman. So far, the site isn't shying away from controversy, with a section on the continuing flap over Bt corn poisoning monarch butterflies (B.A. Palevitz, "Bt or not Bt," The Scientist, 13[21]:1, June 7, 1999). It also chides other countries over trade: "European governments have been slow to permit the importation of biotechnology-derived products, even if they have been proven safe to human and animal health and the environment. This has created friction with the [United States] and other trading partners, who believe sound science should be the basis of regulatory systems. The failure of other countries to develop consistent and science-based regulatory processes governing biotechnology has the potential to constrain scientific innovation and disrupt trade." USDA spokesperson Maria Bynum says the site is a work in progress: "We will continually evaluate the site to determine if it should offer more links, if changes should be made, and/or if material needs to be updated."--Barry A. Palevitz HELPING HAND The chaperone molecule GroEL, which assists protein folding, is not as promiscuous as once thought, according to Ulrich Hartl, professor of cellular biochemistry at the Max-Planck-Institut für Biochemie, Martinsried, Germany (W.A. Houry et al., "Identification of in vivo substrates of the chaperonin GroEL," Nature, 402:147-54, Nov. 11, 1999). GroEL and its cofactor GroES bind to form a cylindrical compartment that isolates a protein. This prevents aggregation with other molecules while the protein is folding (S. Bunk, "Mysteries unravel of protein-folding machine," The Scientist, 13[11]:9, May 24, 1999). Hartl and his colleagues have now found that about 300 of the 4,300 Escherichia coli proteins interact with GroEL. Of this subset, the German group has identified 50 proteins that represent enzymes from various metabolic pathways and the translation/transcription machinery. "Even if GroEL and GroES are required for the folding of a small number of these [proteins], it is clear why this is the only essential chaperonin found in E. coli so far," comments Hartl. Despite the functional variety, there seems to be a preference for a reoccurring structural motif in these proteins. This architecture includes flat beta sheet regions with extensive hydrophobic surfaces that are packed against the hydrophobic faces of alpha helices. Hartl suggests that these proteins may be dependent on a chaperonin because they fold relatively slowly and expose extensive hydrophobic surfaces during folding that would give rise to aggregation.--Nadia S. Halim MAPPING MALARIA Two recently completed maps of malaria chromosomes could help sequencers finish the parasite's genome faster. Each group employed a separate mapping strategy, yielding two different but complementary "scaffolds" that will aid sequencers in the painstaking assembly process. One group used restriction enzymes, molecular scissors that snipped the parasite's DNA into about a thousand segments (Z. Lai et al., "A shotgun optical map of the entire Plasmodium falciparum genome," Nature Genetics, 23:309-13, November 1999). David C. Schwartz, a chemist and geneticist at the University of Wisconsin, Madison, who led that effort, notes that the restriction enzyme mapping holds an advantage over expressed sequence tag (EST) mapping. Although EST maps contain an ordered set of markers, restriction enzyme maps give distances between each genetic landmark on the map--something that EST maps don't provide. In the case of malaria at least, those landmarks proved less than spectacular, providing no unusual features. "It looked as plain Jane as you could imagine," Schwartz says of the map. "We were a little disappointed with that." Thomas E. Wellems, head of the Malaria Genetics Section at the National Institute of Allergy and Infectious Diseases and leader of the other mapping group, was more impressed with his colleagues' project, calling it "a restriction map on steroids." Wellems' group, collaborating with colleagues at the National Center for Biotechnology Information, constructed what he calls "a true genetic linkage map" using microsatellites--a geneticist's slang for short repeats--to place approximately a thousand markers (X. Su et al, "A genetic map and recombinant parameters of the human malaria parasite Plasmodium falciparum," Science, 286:1351-3, Nov. 12, 1999.). "These microsatellites are wonderful," Wellems explains. "They pepper the P. falciparum chromosomes." Microsatellites serve as markers that can be accurately located by genetic recombination patterns. Those markers are already proving useful for gene hunters who use laboratory crosses or field malaria strains to home in on important chromosome sequences that affect disease severity. Both the physical and genetic maps, used together, could prove helpful to assemblers, Wellems believes. When sequencers identify microsatellites in their contigs, they can place those short stretches of sequences on the genetic map. Then they can look at restriction sites and see if the patterns match with the optical map. The two together will aid in "finishing" or closing unsequenced gaps. "For P. falciparum, that's very difficult, because it doesn't sequence as easily as many of the other organisms," Wellems concludes.--Paul Smaglik

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