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The White laboratory focuses on the physiological implications of signaling through various ligand-regulated transcription factors, most recently the vitamin D receptor (VDR) and the aryl hydrocarbon receptor (AHR). Vitamin D is obtained naturally from limited dietary sources or photochemical conversion in skin exposed to adequate levels of ultraviolet B radiation. The active form of vitamin D induces DNA binding, and controls transcriptional regulation by the VDR, thus acting as a 鈥済ene switch鈥�. The lab was the first to use microarray technology to study gene regulation by vitamin D to investigate the mechanisms underlying its physiological effects. Collectively, this work has identified over 1000 novel target genes of vitamin D signaling. It also opened up the field of study of vitamin D as a regulator of human innate immunity, which has implications for roles of vitamin D sufficiency in protection against upper respiratory tract infections and defects in innate immune homeostasis such as the inflammatory bowel condition Crohn鈥檚 disease. The laboratory has also made several seminal contributions to understanding the molecular basis of the putative cancer-preventive activities of vitamin D, work that has been borne out by recent meta-analyses of the results of large-scale RCTs of vitamin D supplementation. More recently, we have聽been studying the AHR, which functions as an environmental sensor and has emerged as a key regulator of immunity. The AHR can be regulated by ligands produced by the photochemical effects of ultraviolet irradiation, and our recent work has shown that the AHR can be activated systemically by exposure of skin to moderate levels of UV light.