Sunlight exposure has been shown to affect epigenetic processes like DNA methylation across several human cell-types, including T-lymphocytes. Since DNA methylation can establish gene expression profiles and affect human health, the role of sunlight exposure in establishing methylation patterns warrants investigation. Dr. Stella Aslibekyan, assistant professor in the department of epidemiology at the University of Alabama at Birmingham—collaborating with department colleagues Ms. Jin Sha, Statistician I, and Dr. Donna K. Arnett, professor and chair, along with Dr. Degui Zhi, assistant professor in the department of biostatistics, section on statistical genetics—recently assessed the effects of sunlight exposure on CD4+ T-cell methylation patterns on an epigenome-wide scale in a North American population of European origin. In addition, they investigated whether the observed epigenetic changes were also due to genetic (sequence) variation.
[Photo: Dr. Stella Aslibekyan]
Dr. Aslibekyan and the team used linear regression to test the associations between methylation scores at 461 281 cytosine-phosphate-guanine (CpG) sites and sunlight exposure, followed by a genome-wide association analysis to test whether the methylation at the top loci was also underpinned by sequence variants. They observed that sunlight exposure was significantly associated with the methylation of cg26930596, a CpG site located in protein kinase C zeta (PRKCZ), which is a biologically relevant gene previously shown to be entrained by light. In addition to sunlight, they found that PRKCZ methylation is also affected by two genetic polymorphismson chromosome 3, rs4574216 and rs4405858. These common genetic variants reside downstream of WWTR1, a transcriptional co-activator of PRKCZ. Despite the high biological relevance of these findings, however, the associations observed in the North American population did not replicate in an independent Mediterranean cohort, likely due to differences in sunlight exposure patterns, age, and lifestyle between the two populations.
Preliminary results support the role of sunlight exposure in epigenetic processes and lay the groundwork for future studies of the molecular link between sunlight and physiologic processes such as tumorigenesis and metabolism. “PRKCZ Methylation Is Associated with Sunlight Exposure in a North American but Not a Mediterranean Population” was published online in July in Chronobiology International.
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