These genes shape your fingerprints and limbs
On the map at our fingertips is a complex and diverse landscape. The swirling maze of tiny ridges, peaks and valleys are used to help us turn the pages of a book, feel and distinguish textures, and unlock our phones. But it turns out that fingerprints aren’t just unique signatures of our identity; these are signatures of our early stages of development.
A recent study published in the journal Cell reveals that genes involved in limb development are influential in shaping the shape of our fingerprints. Previously, researchers believed that the genes active in skin formation were the most obvious link with fingerprints.
“Fingerprints are an interesting feature of human biology that have been used for practical purposes such as individual identification and, more in the past, diagnosis of conditions,” says Denis Headon, study co-author and biologist. of Development at the University of Edinburgh, which studies the genetics of variations in skin structure in different species, such as hair, feathers and scales. “I think what we’re getting here is a glimpse into how fingerprint variation occurs and how it has to do with member development processes.”
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The early skin of an embryo is fairly straightforward, Headon explains. On different areas of the body, the embryonic skin will develop hair follicles, teeth, or in this case, fingerprint ridges on the soles of the feet and the palms of the hands. In an extensive DNA analysis of more than 23,000 people from ethnic groups, Headon and a team of international researchers explored the genetic basis for the unique variations of the trait.
The uniqueness of a fingerprint can be traced back to some very fine features. One example is the exact position of the ridges that cross the fingers, Headon says. “You can get a split in the ridge, where it splits in half, or a ridge can just stop. Sometimes you get very short ridges, like small islands. While not explored in this article, the sweat glands that decorate the tops of ridges also influence their path, Headon adds. However, many of our fingerprints generally fall under three common patterns: whorled, arched, or curly.
“You can have more complicated prints with double whorls, you can have complex loops, but they still fit into those categories, arc, loop, and whorl. And that’s what we’ve been studying here with genetics, ”Headon explains.
The team evaluated the DNA of their volunteers to find the genetic basis of these patterns, looking for a specific balance of genes that alters the odds of having an arc versus a loop versus a whorl. What they found was that many of the genes underlying the formation of the three patterns were not primarily related to skin formation, but rather to the formation of limbs and fingers. To test this discovery, the researchers focused on EVI1, a known gene in limb development in humans that affects the three middle fingers of the hand. They decrease the expression of EVI1 in mice, which do not have fingerprints but have distinct ridges that cross parts of the fingers, and saw that individuals with the altered gene also exhibited changes in the patterns of the ridges. “It’s subtle… but we can see a change in the shape of these transverse ridges,” Headon explains. “This supports the idea that EVI1 is the gene responsible for influencing fingerprint typing in humans, as well as those simple crests we see in mice. “
What this tells us [in humans] is that the distinction between arch, curl, and whorl comes from the way the limb grows and forms, and in particular how the fingers form and develop, in utero before birth.
The limbs of an embryo begin to develop around the fifth week of development. As different bony elements and parts of the fingers of the hand begin to take shape, the genes that form the limbs and also determine the fingerprints are already in action much earlier than the fingerprint begins to appear, Headon explains. Around week 8-10 of development, the hands and feet develop palmar pads – temporary thick skin on the palms and soles of the feet that are particularly prominent as the fingertips and toes develop. Most humans lose their palmar pads before birth, but some animals retain them, such as primates. The bulbous pad “almost looks like a frog’s hand,” Headon explains.
“It was suggested in the 20th century that the shape of these pads – their height, specific shape, and size – influence where the type of fingerprint is formed,” Headon explains. The team’s analysis indicated that finger length is genetically linked to fingerprint patterns. Thus, the researchers deduce that the length of the finger and the size, position and formation of the palmar pad all contribute to the resulting arrangement of fingerprints. “The genetic influence on the distinction of arcs, loops and whorls occurs at this early stage in the construction of the field where the fingerprint will form.”
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The genes that direct fingerprint formation can be useful in learning more about diseases and genetic conditions, Headon explains. While molecular tools are better for diagnosis, exploring the genetic underpinnings of these models could be used to better understand certain chromosomal disorders where fingerprints and folds of the hands are altered, such as Edwards Syndrome and Syndrome. from Down. But Headon points out that there are limits and overuse of fingerprints in some medical assessments. “In psychology, people have already published that certain types of fingerprints are associated, for example, with schizophrenia,” he says. “I am very skeptical about this research. Yet, he adds, these recent discoveries about the genetic origins of our fingerprints can reveal a lot about healthy human development.
“These genetic approaches in large populations can provide insight into developmental processes that take place in humans that are really largely hidden,” he says. “I hope that this type of study can be applied to other characteristics in humans and give further information on how we develop and how we vary from each other.”