When is a mouse like a shark?
When you eliminate the gene Cbfa1.
True, it's not the funniest riddle around, but bone researchers may enjoy it. Mice missing the Cbfa1 gene don't form bones, which leaves them with a skeleton made only of cartilage, like sharks. Unlike sharks, however, mice need a bony skeleton, so the unfortunate rodents die at birth.
Four reports in the May 30 Cell and one scheduled for the July 1 Journal of Cellular Biochemistry describe the discovery that Cbfa1 is vital to bone-forming cells, or osteoblasts.
"I think its the most wonderful series of papers I've seen in a long time," says Jane E. Aubin, an osteoblast researcher at the University of Toronto.
The new findings offer "a very compelling, exciting, and solid story on bone development," adds Bjorn R. Olsen of Harvard Medical School in Boston.
Olsen and his group came across Cbfa1 during a search for the genetic mutations that cause cleidocranial dysplasia syndrome (CCD), a rare human skeletal disorder. As infants grow, bone formation closes several soft spots in the skull. In people with CCD, those spots remain open. Many also lack a clavicle or major portions of it, a defect that allows some of them to bring their shoulders together below their chin.
"We were interested in this disorder because we thought it might tell us something about bone formation," says Olsen.
As his team hunted for the CCD gene, Olsen heard that two other groups had created mice with a similar skeletal disorder by mutating the mouse Cbfa1 gene. The human version of this gene lies in the chromosome 6 region where Olsen's group was looking. The investigators report in Cell that people with CCD have mutations in one of their two copies of Cbfa1.
Two other reports in Cell, one from a research group led by Toshihisa Komori of Osaka University in Japan and the other from a group headed by Michael J. …