A study conducted by the National Institutes of Health and the University of Alabama, Birmingham, has found a link between genes that warn our bodies of a pathogenic infection and genes that play a role in determining hair color.
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The study was recently published in the PLOS Biology journal and uncovered details into what might cause hair to turn gray when people are exposed to chronic stress or severe illness.
When the body encounters a virus, the first line of defense is the innate immune system. Each cell in the human body contains receptors that are capable of identifying harmful viruses and bacteria.
Upon binding to a foreign molecule, cells release signaling molecules called interferons, which prompt stimulate gene expression in other cells for increasing host defenses, turning on immune effector cells, and inhibiting viral replication.
The researchers discovered that the the transcription factor MITF, which is involved in the regulation of the innate immune system, can cause changes to hair pigmentation. Their finding was unexpected.
Genomic tools allow us to assess how all of the genes within our genome change their expression under different conditions, and sometimes they change in ways that we don't anticipate. We are interested in genes that affect how our stem cells are maintained over time. We like to study gray hair because it's an easy read-out of melanocyte stem cell dysfunction."
Melissa Harris, UAB
Melanocyte stem cells play a key role in hair pigmentation as they make the melanocytes that produce and release pigment into the hair shaft.
The study found that, although MITF is most commonly associated with regulating the numerous functions within melanocytes, it also helps control the melanocytes’ interferon response.
Hair can turn gray when the MIFT’s are unable to regulate this interferon response. Moreover, when innate immune signaling was simulated in rodent models susceptible to losing hair pigmentation, more gray hairs were observed.
This new discovery suggests that genes that control pigment in hair and skin also work to control the innate immune system. These results may enhance our understanding of hair graying. More importantly, discovering this connection will help us understand pigmentation diseases with innate immune system involvement like vitiligo."
William Pavan, National Human Genome Research Institute (NHGRI)
Vitiligo is responsible for causing discolored skin patches, and has a prevalence of 0.5% to 1% worldwide. However, the question remains as to why susceptibility to gray hair and susceptibility to dysregulated innate immune signaling are correlated in mice models.
The team surmise that this might shed light on what causes premature graying of hair, and they continue to pursue this question.