" "
Satellite Banner
Technology
Networks
Scientific Communities
 
Become a Member | Sign in
Home>News>This Article
  News
Return

Researchers Identify Genomic Variant Associated with Sun Sensitivity, Freckles

Published: Tuesday, November 26, 2013
Last Updated: Monday, November 25, 2013
Bookmark and Share
NIH-funded work finds genetic switch for pigmentation trait in non-coding, regulatory region of newly associated gene.

Researchers have identified a genomic variant strongly associated with sensitivity to the sun, brown hair, blue eyes - and freckles. In the study of Icelanders the researchers uncovered an intricate pathway involving the interspersed DNA sequence, or non-coding region, of a gene that is among a few dozen that are associated with human pigmentation traits.

The study by an international team including researchers from the National Institutes of Health was reported in the Nov. 21, 2013, online edition of the journal Cell.

It is more common to find people with ancestors from geographic locations farther from the equator, such as Iceland, who have less pigment in their skin, hair and eyes.

People with reduced pigment are more sensitive to the sun, but can more easily draw upon sunlight to generate vitamin D3, a nutrient essential for healthy bones.

The researchers, including scientists from the National Human Genome Research Institute (NHGRI), a part of NIH, analyzed data from a genome-wide association study (GWAS) of 2,230 Icelanders. A GWAS compares hundreds of thousands of common differences across individuals' DNA to see if any of those variants are associated with a known trait.

"Genes involved in skin pigmentation also have important roles in human health and disease," said NHGRI Scientific Director Dan Kastner, M.D., Ph.D. "This study explains a complex molecular pathway that may also contribute insights into skin diseases, such as melanoma, which is caused by the interaction of genetic susceptibility with environmental factors."

The GWAS led the researchers to focus on the interferon regulatory factor 4 (IRF4) gene, previously associated with immunity. IRF4 makes a protein that spurs production of interferons, proteins that fight off viruses or harmful bacteria.

The researchers noted from genomic databases that the IRF4 gene is expressed at high levels only in lymphocytes, a type of white blood cell important in the immune system, and in melanocytes, specialized skin cells that make the pigment melanin. The new study established an association between the IRF4 gene and the pigmentation trait.

"Genome-wide association studies are uncovering many genomic variants that are associated with human traits and most of them are found in non-protein-coding regions of the genome," said William Pavan, Ph.D., co-author and senior investigator, Genetic Disease Research Branch, NHGRI. "Exploring the biological pathways and molecular mechanisms that involve variants in these under-explored portions of the genome is a challenging part of our work. This is one of a few cases where scientists have been able to associate a variant in a non-coding genomic region with a functional mechanism."

The Icelandic GWAS yielded millions of variants among individuals in the study. The researchers narrowed their study to 16,280 variants located in the region around the IRF4 gene. Next, they used an automated fine-mapping process to explore the set of variants in IRF4 in 95,085 people from Iceland. A silicon chip used in the automated process enables a large number of variants to be included in the analysis.

The data revealed that a variant in a non-coding, enhancer region that regulates the IRF4 gene is associated with the combined trait of sunlight sensitivity, brown hair, blue eyes and freckles. The finding places IRF4 among more than 30 genes now associated with pigmentation, including a gene variant previously found in people with freckles and red hair.

Part of the research team, including the NHGRI co-authors, studied the IRF4's role in the pigment-related regulatory pathway. They demonstrated through cell - culture studies and tests in mice and zebrafish that two transcription factors - proteins that turn genes on or off-interact in the gene pathway with IRF4, ultimately activating expression of an enzyme called tyrosinase.

One of the pathway transcription factors, MITF, is known as the melanocyte master regulator. It activates expression of IRF4, but only in the presence of the TFAP2A transcription factor. A greater expression of tyrosinase yields a higher production of the pigment melanin in melanocytes.

"This non-coding sequence harboring the variant displayed many hallmarks of having a function and being involved in gene regulation within melanocyte populations," said Andy McCallion, Ph.D., a co-author at Johns Hopkins University, Baltimore, and collaborator with the NHGRI group.

The newly discovered variant acts like a dimmer switch. When the switch in the IRF4 enhancer is in the on position, ample pigment is made. Melanin pigment gets transferred from melanocytes to keratinocytes, a type of skin cell near the surface of the skin, and protects the skin from UV radiation in sunlight.

If the switch is turned down, as is the case when it contains the discovered variant, the pathway is less effective, resulting in reduced expression of tyrosinase and melanin production. The exact mechanism that generates freckling is not yet known, but Dr. Pavan suggests that epigenetic variation-a layer of instructions in addition to sequence variation-may play a role in the freckling trait.

More research is needed to determine the mechanism by which IRF4 is involved in how melanocytes respond to UV damage, which can induce freckling and is linked to melanoma, the type of skin cancer associated with the highest mortality.


Further Information

Join For Free

Access to this exclusive content is for Technology Networks Premium members only.

Join Technology Networks Premium for free access to:

  • Exclusive articles
  • Presentations from international conferences
  • Over 2,900+ scientific posters on ePosters
  • More Than 4,200+ scientific videos on LabTube
  • 35 community eNewsletters


Sign In



Forgotten your details? Click Here
If you are not a member you can join here

*Please note: By logging into TechnologyNetworks.com you agree to accept the use of cookies. To find out more about the cookies we use and how to delete them, see our privacy policy.

Related Content

Visualizing a Cancer Drug Target at Atomic Resolution
Using cryo-electron microscopy, researchers were able to view, in atomic detail, the binding of a potential small molecule drug to a key protein in cancer cells.
Wednesday, February 10, 2016
Tick Genome Reveals Secrets of a Successful Bloodsucker
NIH-funded study could lead to new tick control methods.
Tuesday, February 09, 2016
Genomic Signature Shared by Five Types of Cancer
National Institutes of Health researchers have identified a striking signature in tumor DNA that occurs in five different types of cancer.
Monday, February 08, 2016
Natural Protein Points to New Inflammation Treatment
Findings may offer insight to effective treatments for inflammatory diseases, such as rheumatoid arthritis, psoriasis, and multiple sclerosis.
Friday, February 05, 2016
Cancer Drug Target Visualized at Atomic Resolution
New study using cryo-electron microscopy shows how potential drugs could inhibit cancer.
Thursday, February 04, 2016
Genome-Wide Study Yields Markers of Lithium Response
An international consortium of scientists has identified a stretch of chromosome that is associated with responsiveness to the mood-stabilizing medication lithium among patients with bipolar disorder.
Monday, February 01, 2016
Schizophrenia’s Strongest Known Genetic Risk Deconstructed
Suspect gene may trigger runaway synaptic pruning during adolescence – NIH-funded study.
Thursday, January 28, 2016
Experimental Combination Surprises with Anti-HIV Effectiveness
A compound developed to protect the nervous system from HIV surprised researchers by augmenting the effectiveness of an investigational antiretroviral drug beyond anything expected.
Monday, January 25, 2016
Dengue Vaccine Enters Phase 3 Trial
Investigational vaccine to prevent ‘breakbone fever’ developed at NIH.
Friday, January 15, 2016
NIH Genome Sequencing Program Targets the Genomic Bases of Common, Rare Disease
The National Institutes of Health will fund a set of genome sequencing and analysis centers whose research will focus on understanding the genomic bases of common and rare human diseases.
Friday, January 15, 2016
Trying to Conceive Soon After a Pregnancy Loss May Increase Chances of Live Birth
NIH study finds no reason for delaying pregnancy attempts after a loss without complications.
Wednesday, January 13, 2016
Three Glaucoma-Related Genes Discovered
NIH-funded genetics analysis of glaucoma is largest to date.
Tuesday, January 12, 2016
NIH-funded Memory Drug Moves into Phase 1 Clinical Study
Collaboration between NIH and Tetra Discovery Partners leads to development of treatment that may affect cognition.
Monday, January 04, 2016
International Study Reveals New Genetic Clues to AMD
NIH-funded research provides framework for future studies of AMD biology, therapy.
Tuesday, December 22, 2015
NIH Unveils FY2016–2020 Strategic Plan
Detailed plan sets course for advancing scientific discoveries and human health.
Thursday, December 17, 2015
Scientific News
Head Injury Patients have Protein Clumps Associated with Alzheimer’s Disease
Scientists have revealed that protein clumps associated with Alzheimer's disease are also found in the brains of people who have had a head injury.
Exposure to Air Pollution 30 Years Ago Associated with Increased Risk of Death
Exposure to air pollution more than 30 years ago may still affect an individual's mortality risk today, according to new research from Imperial College London.
More Then 1 in 20 U.S. Children have Dizziness and Balance Problems
Researchers at NIH have found that girls have a higher prevalence of dizziness and balance problems compared to boys, 5.7 percent and 5.0 percent.
Biosensors on Demand
New strategy results in custom "designer proteins" for sensing a variety of molecules.
Low-Cost, Portable NQR Spectroscopy
A researcher at Case Western Reserve University is developing a low-cost, portable prototype designed to detect tainted medicines and food supplements that otherwise can make their way to consumers. The technology can authenticate good medicines and supplements.
Structure of Brain Plaques in Huntington's
Researchers at the University of Pittsburgh School of Medicine have shown that the core of the protein clumps found in the brains of people with Huntington's disease have a distinctive structure, a finding that could shed light on the molecular mechanisms underlying the neurodegenerative disorder.
Insights into the Function of the Main Class of Drug Targets
About thirty percent of all medical drugs such as beta-blockers or antidepressants interact with certain types of cell surface proteins called G protein coupled receptors.
Spero Therapeutics Announces $30 Million Series B Preferred Financing
Company has announced financing of $30 million to support development of novel therapies to treat gram-negative bacterial infections.
Unique Mechanism for a High-Risk Leukemia
Researchers uncovered the aberrant mechanism underlying a notoriously treatment-resistant acute lymphoblastic leukemia subtype; findings offer lessons for understanding all cancers.
Visualizing a Cancer Drug Target at Atomic Resolution
Using cryo-electron microscopy, researchers were able to view, in atomic detail, the binding of a potential small molecule drug to a key protein in cancer cells.
Scroll Up
Scroll Down
Skyscraper Banner

Skyscraper Banner
Go to LabTube
Go to eposters
 
Access to the latest scientific news
Exclusive articles
Upload and share your posters on ePosters
Latest presentations and webinars
View a library of 1,800+ scientific and medical posters
2,900+ scientific and medical posters
A library of 2,500+ scientific videos on LabTube
4,200+ scientific videos
Close
Premium CrownJOIN TECHNOLOGY NETWORKS PREMIUM FOR FREE!