Understanding gene expression signatures with pigmentation changes in Melanocytes

This microarray experiment was performed for identifying the signaling pathways that could be differentially regulated in response to changes in the pigmentation levels in human melanocytes. Melanocytes were either treated with pigmentation inducing agent or depigmenting compound targeting tyrosinase (key enzyme involved in the melanogenesis). The samples were then processed for analyzing the differentially regulated signaling pathway by performing microarray on agilent platform. The pathway enrichment analysis was executed on DAVID software. The plot has been generated using the average enrichment score for the pathways under similar category of function. Interestingly, along with the expected melanogenic and cAMP pathways, we observed differential regulation of Ca2+ signaling during pigmentation. We then performed several experiments for evaluating the contribution of cytoplasmic and endoplasmic reticulum (ER) Ca2+ homeostasis to pigmentation. After extensive studies in in vitro and in vivo pigmentation models, we demonstrate a critical role for ER Ca2+ sensor, STIM1 protein in the process of pigmentation. Taken together, we performed the microarray experiment for identifying potential pathways wherein Ca2+ homeostasis came out as one of the several hits. We then specifically studied cytoplasmic and endoplasmic reticulum (ER) Ca2+ homeostasis and identified a novel regulator of pigmentation based on several lines of evidences including in vivo model system Melanocytes were treated with differentially pigmenting agents Tyrosine (the substrate of pigmentation to increase pigmentation), Phenylhiourea( a inhibitor of tyrosinase enzyme involved during pigment synthesis to suppress pigment syntheis) for 48 hours in culture media. All treatments were given 24 hours post seeding the cells in T25 flasks.