The discovery, reported today (July 11) in the British journalNature, promises key insight into how genes in animals, including humans, direct limb formation, said Sean B. Carroll of the Howard Hughes Medical Institute at the University of Wisconsin-Madison and a lead author of the study.
"It came to us as a surprise that a single gene appears to regulate the formation of wings," Carroll said. "We thought it would be a hodgepodge, that no single thing could have controlled this."
Finding out how genes, acting during embryonic stages of development, direct featureless cells to become arms, legs, eyes, wings and other body parts is a major quest of modern molecular biology. While the new finding has no immediate application, it promises a fundamental understanding of how genes mastermind the development of limbs, and may open new avenues to the prevention of the genetic miscommunication that leads to birth defects.
"We've clearly got our hands on one of the crucial genes," said Carroll. "It will enable us to get into the guts of the system" that controls limb formation.
Known as the "vestigial gene," the new gene is extremely potent and must be tightly controlled in order for it to correctly direct other genes to make wing cells in the right place at the right time.
"Because it makes wing tissue, you only want the gene to be turned on in certain places," Carroll said. "It is so powerful you have to control it to make sure you dont grow wings all over." The paper published today in Nature, written by a team of UW-Madison biologists that also includes post-doctoral fellow Jaeseob Kim and graduate student Angela Sebring, details how the gene controls its function. It is that finding, said Carroll, that allowed the Wisconsin scientists to grow clumps of wing tissue virtually anywhere on the body of the developing fruit flies. The control system, said Carroll, could be likened to a switchboard, able to direct genetic signals in time and space. Importantly, the system is almost the same in vertebrates, including humans: "It seems to be a built-in component of the vestigial gene. These same cues control where you put things in vertebrates. "The genetic machinery is very old. The way cells talk to each other in insects and humans is essentially the same. Some general principles are being worked out here." The genetic system that governs limb formation, according to Carroll, probably arose several hundred million years ago in a distant ancestor of both flies and humans. The system is apparently conserved today in both insects and vertebrates. If general principles are worked out in detail, and hold true for vertebrates, it raises the possibility that one day at least some congenital defects can be prevented.
Wings From Eyes
Clumps of wing tissue, in response to genetic cues given in the laboratory,
sprout from the eyes of a fruit fly. Wing tissue growth in insects seems to
be governed by a single gene, a discovery that not only enables scientists
to direct the growth of wing tissue from appendages like eyes and legs, but
promises key insight into how genes in animals, including humans, direct
the growth and development of arms, legs and other limbs.
Photo Credit: Angela Sebring, University of Wisconsin-Madison
Terry Devitt, (608) 262-8282; trdevitt@facstaff.wisc.edu