Chew on this: mutation may be responsible for tooth loss, colon cancer.

A decade ago, scientists sometimes explained the ABCs of genetics with the simple rule that each gene has one function. Today, this nice, neat and, as some would say, naive concept appears to have fallen largely out of favor. In its place, researchers have fashioned the concept in which a gene typically has multiple functions and/or physiologic effects, sometimes in seemingly unrelated parts of the body. Just how seemingly unrelated can these manifestations be? Recently, a team of Finnish scientists reported discovering a large family that is predisposed to both colon cancer and a rare congenital dental malformation. They say the cause is a specific mutation in a gene called AXIN2, which is selectively expressed in certain types of organ development and also has a regulatory role in cell homeostasis. In essence, the mutation seems to disrupt tooth development early in life and later contributes to the emergence of polyps and eventually colon cancer. According to the scientists, their data mark one of the few known instances in which a gene mutation causes a hypo-plasia in one organ and a hyperplasia in another. Moreover, if their follow-up studies confirm and/or strengthen their existing data, they say dentists may at the very least need to remain aware of the possible association, an example of how molecular genetic discoveries today increasingly cross traditional disciplines. All in the Family Tooth agenesis—the lack of one or more permanent teeth—is the most common congenital malformation in humans. It comes in two main subtypes, one of which is the more severe oligodontia. Although the disease is fairly rare, people with oligodontia do not produce six or more permanent teeth, and these conditions are often associated with other malformations of the nails, hair, and other ectodermal-derived tissues. Given the importance of proper tooth formation across species, a team of researchers at the University of Helsinki has long been interested in identifying genes that might play a role in oli-godontia. That led them a few years ago to a four-generation family, in which about half of the family members lacked at least eight permanent teeth, primarily permanent molars, premolars, and various incisors. After narrowing the location of the altered gene to a specific region of chromosome 17, the scientists noticed something intriguing. Among the candidate genes in this region was AXIN2, whose protein product aligns itself within the wnt signaling pathway. This intensely studied pathway plays a key …