The Top 12 Biology Stories of 2006

Hairy crabs, zapping wounds to heal them, the fastest animal attack, and more

Monday, January 1, 2007

15. Stem Cell Setbacks Inspire New Methods

The year 2006 — the 10th anniversary of Dolly the sheep's birth — began with a severe setback for stem cells' boosters. Some patients, scientists, and politicians had dared hope that cloning technology could be used to create donor-compatible stem cells that can help treat disease. But after learning that work by South Korean scientist Woo Suk Hwang had been faked, the journal Science retracted Hwang's landmark papers from 2004 and 2005, which reported the first human embryonic stem cells from cloned embryos.

Six months after the retraction, stem cell research received another blow. On July 19 President Bush vetoed H.R. 810, the Stem Cell Research Enhancement Act of 2005, which passed both the House and Senate by solid bipartisan majorities. The bill was put forth to loosen the restrictions Bush placed on human embryonic stem cell research on August 9, 2001, when he banned federal funding for work with any stem cell line created after that date. Since then, the vast majority of presidentially approved cell lines have proven unavailable, genetically abnormal, or otherwise difficult to work with. H.R. 810 would have allowed federal funding for work with certain stem cell lines created from excess frozen IVF embryos in the years since. (In polls, 60 percent of Americans disagreed with the president's veto.)

In the face of these setbacks, many scientists have focused on new methods of creating stem cell lines without destroying embryos. Traditionally, the process involves plucking the inner cell mass from a 5-day-old embryo known as a blastocyst (a round ball of 150 to 200 cells the size of a grain of sand), which destroys the embryo. In March however, German researchers — working in a political landscape even more restrictive than our own — reported turning sperm-producing cells from adult mouse testes into something very much like embryonic stem cells. A week later, U.S. scientists claimed to have done the same with human cells. In June Italian scientists announced the first human embryonic stem cells derived from parthenotes — embryo-like structures formed when an egg starts to divide on its own, with no sperm involved. In mammals, parthenotes are incapable of implanting in the womb to form a pregnancy and so are not considered potential human lives. Still, parthenotes can yield stem cells that closely match the genetic profile of the egg donor. In August Japanese scientists reported yet another method for making "personalized" cells without cloning: They treated mouse skin cells with four gene products active in embryonic stem cells and got the skin cells to revert to something much like the stem cells. In September a European team reported coaxing human embryonic stem cells from an "arrested" IVF embryo — one that had stopped dividing before it reached the blastocyst stage and thus died a natural death.

One of the biggest uproars followed a report from the biotech company Advanced Cell Technology (ACT), which described creating stem cells from a single cell taken from a 3-day-old, 8-cell human embryo. Single-cell biopsy procedures are done routinely in infertility labs and do not destroy the embryo, which "takes away the president's last excuse to oppose the research," ACT's vice president of research, Robert Lanza, told reporters.

Critics of embryo research responded with concerns that a biopsy might subtly harm an embryo, and wondered if even that single cell could have the potential to develop into an embryo and therefore a baby. They also attacked the company for a press release that claimed, "We have demonstrated, for the first time, that human embryonic stem cells can be generated without interfering with the embryo's potential for life." That release failed to mention that all 16 of the embryos used in these experiments had been destroyed. The ensuing controversy raised ire even on the pro-research side. "It's a big black eye if scientists are making false and fraudulent representations," Republican senator Arlen Specter, of Pennsylvania, told representatives of ACT during a Senate subcommittee hearing. Specter is a leading proponent of stem cell research and is currently trying to raise enough support for H.R. 810 to override the president's veto. "You made our job a lot tougher," he said.

Kyla Dunn

55. New Mouse Organ Found

Mice are the most common lab animal, dissected so frequently that no biologist expects to stumble upon a new organ. But in April 2006, Hans-Reimer Rodewald, an immunologist at the University of Ulm in Germany, reported that mice have two thymus organs — one of them somehow undiscovered — and that both can produce immune cells called T lymphocytes. Located in the neck, the newfound organ is a fraction of the size of the long-familiar thymus found in the mouse's chest.

"When we first saw this, I didn't believe it," says Rodewald. To see whether it was a true functional organ, his team transplanted the small thymus from normal mice into mutant, thymus-free animals. When they injected these animals with a protein from the hepatitis B vaccine, the animals produced an immune response. Biologists are checking to see if they have overlooked a second human organ too.

Rabiya S. Tuma

64. HIV Precursor Found in the Wild

Researchers have long suspected that chimpanzees were the source of HIV-1, the AIDS virus, but proof from the wild was missing. A team led by Beatrice Hahn, professor of medicine at the University of Alabama in Birmingham, has now detected antibodies against the HIV-1 precursor — along with nucleic acids from the virus itself — in the scat of wild chimps. The HIV-1 progenitor appears to have originated in southern Cameroon, then made its way down the Sangha River to Kinshasa, Democratic Republic of the Congo, where the first documented infections in people occurred.

Nicholas Bakalar

65. Gay Influence Found

Over the past decade, a handful of studies have hinted at a connection between male homosexuality and having older brothers. Now it appears that the key factor is sharing a biological mother.

Anthony Bogaert, a psychologist at Brock University in Ontario, set out to clarify the relative importance of biology and environment in determining sexual orientation. In a study of 944 men, published in July, he found that adopted brothers do not affect sexual orientation. Nor does it matter if a boy lives with his older biological brothers.

Bogaert estimates that one in seven gay men can attribute their homosexuality to having older biological brothers. Each increases the odds of being gay by one third. The base rate for homosexuality in men with no older brothers is estimated at about 4 percent, giving a man with one older brother a 5.2 percent chance of being gay.

"I was surprised that the effects were as strong as they were," Bogaert says. "What really hit home for me was finding evidence that there must be some kind of prenatal biological mechanism." The effect may be due to how a mother's immune system reacts to proteins produced by male fetuses—a possibility Bogaert hopes to explore in a future study.

Stephen Ornes


68. Moss Sex Points To Precursor of Pollination

Biology textbooks claim that the male moss mates by shedding sperm into a surrounding film of rainwater or dew — a haphazard strategy that arose in ancestral aquatic algae. But Swedish researchers announced in September that arthropods may in fact act as go-betweens. Such assisted reproduction was thought to have arisen about 140 million years ago, when insects began collecting and transferring pollen between flowering plants. It now seems that the tactic may have arisen far earlier, about 440 million to 470 million years ago, shortly after plants first colonized land.

Botanist Nils Cronberg of Lund University had suspected that mosses might use an intermediary to mate, so he designed a simple lab experiment to test his idea. He placed male and female mosses of the species Bryum argenteum in vials lined at the base with plaster of paris, which prevented the sperm from swimming. When males and females touched, fertilization occurred; when they were separated by a space three-fourths of an inch to one-and-a-half inches wide, it did not — unless mites and tiny arthropods called springtails were present to shuttle sperm between them. In a further experiment, the arthropods were allowed to choose between either sterile or fertile sperm-laden moss shoots; invariably, they chose the sugar- and fat-rich fertile shoots. "It seems that the animals are doing this because they get some sort of reward," says Cronberg. "This seems to be a phenomenon parallel with pollination."

Josie Glausiusz

73. Electrical Signals Help Direct Wound Healing

In the mid-1800s, after wounding his arm, German physiologist Emil Du Bois-Reymond measured a small current at the site, which suggested that the injury triggered an electric signal. Since then biologists have made little progress in understanding where electricity fits into the myriad chemical and physical responses involved in wound healing. In July Min Zhao, professor of biomedical science at the University of Aberdeen in Scotland, announced that electricity is the dominant factor.

Using an electric current, Zhao and his colleagues were able to direct epithelial cells (like those in the skin and in mucus membranes) both to and from wounded tissue in mouse corneas. In addition, they showed that the speed of the migration is in direct proportion to the amount of voltage applied. It is too soon to endorse experimental therapies that employ electrical stimulation, Zhao says. Rather, his next step is to investigate the healing properties of electricity at the genetic level. His team has already identified two genes that are key players in cell migration. Next they will look for molecules and genes that assist in sensing an electric signal and in mediating the cell's response to it.

Nicholas Bakalar

79. Worm Lives Without Guts

Over the course of evolution, Olavius algarvensis, a bizarre little worm living in sediments along the Mediterranean, appears to have lost its mouth, guts, and excretory organs. Instead, it relies on several species of bacteria that live beneath its skin, forming a web of cooperative relationships with one another and with their host. In September Nicole Dubilier of the Max Planck Institute in Germany and her colleagues reported that they had sequenced the DNA of four of the bacterial houseguests, revealing intimate details about their quid pro quo with the worm. "They're providing energy production," says Edward Rubin, head of the federal Joint Genome Institute in Walnut Creek, California, where the sequencing was done. "They feed the worm, they get rid of the worm's waste." In return, the bacteria get housing and transportation. This was the first genomic analysis of such a complex symbiotic relationship.

Ingfei Chen

80. New Monkey Genus Found in Tanzania

Biologists added a new branch to our primate family tree this year. Genetic studies of the kipunji, a threatened monkey in Tanzania, reveal that it belongs to a new primate genus — the first to be identified in 83 years. The grayish-brown monkey, which is about three feet long with a distinctive "honk-bark" call, lives in a highland habitat that had largely been ignored by scientists. Fewer than 1,000 kipunji may remain. According to Tim Davenport, a biologist for the Wildlife Conservation Society, "had we not found it now, it could very well have slipped into extinction without the scientific world ever knowing of it."

Jennifer Barone

86. A Yeti Crab Discovered

A furry-looking crustacean discovered on the floor of the South Pacific Ocean at a depth of 6,500 feet is so unusual that it has earned itself a brand-new taxonomic family: Kiwaidae. The six-inch-long white crab is eyeless, and its claw arms are covered with hairlike filaments filled with what are most likely symbiotic bacteria. Joe Jones of the Monterey Bay Aquarium Research Institute codiscovered the crab — which he calls Yeti, after the mythical abominable snowman — while he and his colleagues were exploring hydrothermal vents using the submersible vehicle Alvin.

Jennifer Barone

88. Super-Ants Fly by Force of Mouth

Hollywood may have run out of ideas about how to reimagine Superman, but nature has not. This year biologists published a study of super-ants that fly by biting against the ground so hard that they shoot themselves into the air. To generate the necessary force, they prop apart their large, pincerlike mandibles with a latch on their heads, tense their muscles, and release the latch. The mandibles then accelerate together at a terrific rate, like the sudden movement of a person's finger during a snap. High-speed 70,000-frames-per-second video analysis of the bites shows that the ants have the fastest self-propelled strike in the animal kingdom, beating even the snapping shrimp.

Amos Kenigsberg

91. Cancer Morphs Into New Life-Form

More than 20 years after University College London's viral oncologist Robin Weiss read about an odd, sexually transmitted cancer in dogs, he has turned up surprising clues about its origin in a canine ancestor hundreds, or possibly thousands, of years ago.

The tumors, which appear on dogs' genitals, seem to get passed along during mating; some early genetic evidence had hinted that the tumors migrated from dog to dog, as if transplanted. To find out, Weiss and veterinarian Claudio Murgia collected and analyzed the DNA of tumor specimens (above) from dog breeds all over the world. None of the tumors matched the DNA of the dogs they had been taken from. Instead, the cells proved to be descendants from a single original tumor that has been spreading via body fluids and sexual contact from one dog to the next over generations. The tumors are a medical curiosity, constituting the oldest-known mammalian cell line in existence, as well as a novel type of parasite so unusual that it may not fit into any current classification.

Similar cancer lines could exist in other animals, including humans, but Weiss expects that they are rare. Most cells from a foreign donor, such as in transplanted organs, are targeted by the immune system, but "this one has found a way to suppress the immune system of its hosts long enough to let it be passed along," he says.

Jocelyn Selim

97. DNA Boosts Panda Count

A new census based on DNA analysis of panda feces suggests that there may be 3,000 giant pandas living in China, twice as many as was previously thought. Prior to this study, counting pandas was as much an art as a science: Pieces of bamboo in panda droppings were inspected for bite marks to distinguish individual bears. But nibbles from different pandas may look similar, so researchers tended to underestimate the population, according to conservation geneticist Michael Bruford of Cardiff University in Wales. "We are not saying the panda is out of the woods," he says, but with conservation efforts "the long-term prognosis is much more favorable for the future of the species."

Jennifer Barone

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