Mammal mapping projects to move forward

In the coming months, scientists will begin sequencing the genomes of nine more mammals, including the domestic cat, guinea pig, rabbit, orangutan, and elephant, according to the National Human Genome Research Institute. In addition, nine other organisms have received the green light to be sequenced as part of the institute's large-scale sequencing research network.

In a shift from the NHGRI's previous procedure of choosing sequencing targets one at a time on the basis of proposals from scientists, the National Advisory Council for Human Genome Research, a federally chartered committee that advises NHGRI, recently approved a comprehensive plan that identified two groups on the basis of their collective scientific merits.

"Science tells us that the most effective approach we currently have to identify the essential functional and structural components of our own genome is to compare it with the genomes of other organisms. With each new genome that we sequence, we move closer to the goal of finding all of the crucial elements of the human genome involved in development, health, and disease," said Mark Guyer, PhD, director of the division of extramural research at the NHGRI. "We hope to accelerate that process with our new sequencing strategy that identifies the organisms, or sets of organisms, with the greatest potential to fill gaps in our knowledge."

The agency selected the nine mammals in the first group because each species represents an important position on the evolutionary tree and, therefore, will contribute a sequence that will be particularly important in helping to interpret the human genome.

The data from seven of these mammalian genomes will be used primarily in the identification of features that are similar, or conserved, among the genomes of humans and other mammalian species. Conservation suggests that a sequence constitutes a functionally important region of the genome.

The seven mammals in this subset are the African savannah elephant (Loxodonta africana), European common shrew (Sorex araneus), European hedgehog (Erinaceus europeaus), guinea pig (Cavia porcellus), lesser hedgehog tenrec (Echinops telfairi), nine-banded armadillo (Dasypus novemcinctus), and rabbit (Oryctolagus cuniculus).

An eighth animal, the domestic cat (Felis catus), will add valuable data to the subset, but was selected primarily because of its importance as a medical model for studying disease. The ninth mammal, the orangutan (Pongo pygmaeus), is among the primate species, which are most closely related to humans. NHGRI-supported researchers have already sequenced the chimpanzee (Pan troglodytes) and are sequencing the genome of the rhesus macaque (Macaca mulatta). Scientists will compare and contrast these primate genomes with the human genome to define and understand what DNA sequences set primates apart from other mammals and humans apart from other primates.

The second group chosen for the new sequencing effort comprised nine nonmammalian organisms, each of which represents a position on the evolutionary time line marked by important changes in animal anatomy, physiology, development, or behavior. The organisms include a slime mold (Physarum polycephalum), choanoflagellate (Monosiga ovata), placozoan (Trichoplax adhaerens), cnidarian (Hydra magnipapillata), snail (Biomphalaria glabrata), and two roundworms (Pristionchus pacificu and Trichinella spiralis).

"Over the past few years, comparative analysis has emerged as an extremely powerful tool for deciphering the human genome sequence," said Jane Peterson, PhD, associate director of the division of extramural research at the NHGRI. "Now, with the data generated by our more systematic approach to selecting sequencing targets, researchers can look forward to using that tool with greater precision and efficiency."

In recent years, the large-scale genome sequencing project has focused efforts on sequencing the genomes of the human, chimpanzee, dog, mouse, rat, chicken, honeybee, two fruit flies, the sea urchin, two puffer fish, two sea squirts, two roundworms, several fungi, baker's yeast, and many prokaryotes, including Escherichia coli. Additional organisms already in the NHGRI sequencing pipeline are the macaque, kangaroo, cow, gray short-tailed opossum, red flour beetle, flatworm Schimdtea mediterranea, and additional species of fruit fly and fungi.