The long noncoding RNA MALAT1 suppresses miR-211 to confer protection from ultraviolet-mediated DNA damage in vitiligo epidermis by upregulating sirtuin 1

Background The absence of melanocytes poses a challenge for long-term tissue homeostasis in vitiligo. Surprisingly, while individuals with Fitzpatrick photo-types I-II (low melanin content) have a higher incidence of melanoma and non-melanoma skin cancer, people with vitiligo are at a decreased risk for the same. Objectives To understand the molecular mechanisms that protect vitiligo skin from ultraviolet (UV)-induced DNA damage by (i) characterizing differentially expressed microRNAs in lesional vs. nonlesional epidermis and (ii) identifying their upstream regulators and downstream gene targets. Methods Genome-wide microRNA profiling of nonlesional and lesional epidermis was performed on five individuals with stable nonsegmental vitiligo using next-generation RNA sequencing. The relevance of the upstream regulator and down-stream target gene of the most differentially expressed microRNA was studied. Results Our study found sirtuin1 (SIRT1), an NAD-dependent deacetylase, to be a direct target of miR-211 - the most significantly downregulated microRNA in lesional epidermis. Inhibition of SIRT1 with EX-527 downregulated keratin 10 and involucrin, suggesting that SIRT1 promotes keratinocyte differentiation. Overexpression of miR-211 mimic led to a significant increase in gamma-H2AX positivity and cyclobutane pyrimidine dimer (CPD) formation, hallmarks of UVB-mediated DNA damage. These effects could be ameliorated by the addition of resveratrol, a SIRT1 activator. Furthermore, a long noncoding RNA, MALAT1, was identified as a negative upstream regulator of miR-211. Overexpression of MALAT1 resulted in increased expression of SIRT1 and a concomitant removal of UVB-induced CPDs in primary keratinocytes. Conclusions These findings establish a novel MALAT1-miR-211-SIRT1 signalling axis that potentially confers protection to the 'amelanotic' keratinocytes in vitiligo.