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February 7, 2008

Dental school researchers study lip prints

To some, a kiss is just a kiss. To researchers in Pitt’s Center for Craniofacial and Dental Genetics, a kiss may offer clues to who may be at increased risk for certain birth defects.

Researchers there are using cheiloscopy, the study of lip prints, as part of their quest to better understand the causes behind cleft lip and palate.

Center director Mary Marazita, who also is the School of Dental Medicine’s associate dean of research and chair of the Department of Oral Biology, has been studying clefting since the 1980s.

Clefts, which occur when the tissue that forms the upper lip and roof of the mouth doesn’t fuse properly during prenatal development, are among the most common birth defects, affecting 1 or 2 of every 1,000 births worldwide. About 30 percent of clefts are associated with a genetic syndrome; the rest are thought to result from other genetic and/or environmental factors.

Marazita’s research includes the Pittsburgh Oral-Facial Cleft Study, which seeks to find the genes underlying non-syndromic clefts by studying families that include at least two affected family members.

Study participants in Pittsburgh and other sites around the world are screened in a lengthy process that includes taking a general health history, family history and DNA sample, 3-D facial photos from which measurements can be calculated, an ultrasound of the muscle of the upper lip, lip prints as well as fingerprints, an assessment of handedness and a screening by a speech pathologist to assess speech architecture.

A number of traits have been found to be more common in families with clefting. Among them are non-right-handedness, physical asymmetry and structural differences in the muscle that surrounds the lip as well as differences in teeth, facial dimensions and speech characteristics. Ethnicity also plays a role. Native Americans and Asians have a higher incidence of non-syndromic clefting while the occurrence is rarer in whites and even less common in blacks.

The idea to study lip prints came about a decade ago as center researcher Kathy Neiswanger, a research professor in the Department of Oral Biology, began paging through the index of “Mendelian Inheritance in Man,” a catalog listing human genes and genetic disorders.

While searching for some simple genetic traits that might be related to clefting or increased risk of clefting, “I hit on lip prints as one of the entries,” she said.

Very little literature on lip prints exists, and most of that is aimed more at determining whether people can be identified by their prints in a manner similar to fingerprinting, or in extracting DNA from lip prints to solve crimes. But Neiswanger found a German research paper from the 1970s indicating that certain types of patterns found in lip prints might be increased in individuals with clefts.

The very low-tech process of gathering research subjects’ lip prints made it easy to choose to add lip printing to the protocol. Marazita decided, “It was cheap and easy to do so we’ll collect it on everybody.”

The prints are taken using invisible ink — the kind used to take hand and footprints of newborns — printed onto chemically sensitive paper that develops in a few minutes.

Neiswanger found that the original lip prints — printed in gray — were difficult to analyze until a post-graduate student scanned the prints and contrast-enhanced them. When the prints were enlarged and colored blue, the patterns became clearer. Now, Neiswanger said, “We’ve seen more lip prints than probably anybody in the world.”

They’ve even had some fun with the prints, combining a sampling of the student’s work in a four-panel Warhol-esque print to present as a Pittsburgh-themed farewell gift when the student left the center for dental school.

Most people have never paid much attention to the patterns on their lips or anyone else’s, but Neiswanger noted that lip prints vary greatly. The simplest pattern is made up of vertical lines, but others include horizontal lines, whorls, diamond patterns, X-shapes or lines that resemble roots and branches.

“There are lots of patterns,” Neiswanger said. “It gets complicated very quickly.”

Parallel research has shown that a mutation in the IRF6 gene causes Van der Woude syndrome — a syndrome that causes clefting and/or circular depressions called fistulas on the lips.

It’s unclear why this gene — an interferon regulatory factor — would have an impact on lips, Marazita said. But the researchers immediately began to wonder whether whorl patterns are associated with variants (differences that are not mutations) in the IRF6 gene. They hypothesize that certain genes in a family could lead to clefting in some members and particular lip prints in others.

“We have to be careful,” Marazita said. “We don’t know yet.”

The center now has a collection of more than 900 lip prints that have been examined to sort out those that have whorl patterns from those that do not.

Early analysis found lower lip whorls in about 18 percent of individuals with clefts and about 16 percent of their family members without clefts. In contrast, only about 3 percent of a control group had whorl patterns, a “very significant finding,” she said.

While the lip prints all have been scored, only about two-thirds of the genotyping is done, so there are no definitive answers yet.

Neiswanger said she hopes to have all the pieces in place in time for a presentation at a meeting of cleft palate researchers in mid-April.

Marazita said that identifying the genes that may predispose some families to clefting could lead to better genetic counseling and improved treatments.

“Once we get the genetics down, we can look at environmental factors,” she said. For instance, smoking during pregnancy is known to double the risk of clefts, but it’s not known whether refraining from smoking could be even more important for those with genetic traits associated with an increased risk.

“Within five years we’ll know enough about some of these traits that they’ll be clinically useful,” Marazita predicted.

—Kimberly K. Barlow

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