Integrative functional genomic analyses identify novel genetic variants influencing skin pigmentation in indigenous Africans [Cut&Run, ATAC-seq]
Skin color is highly variable in Africans, yet little is known about the underlying molecular mechanism. We identified 1,157 candidate variants influencing skin pigmentation in indigenous Africans by genome-wide association studies and scans of natural selection based on differentiation in allele frequencies between lightly pigmented southern African Khoesan populations and other darkly pigmented African populations. We applied massively parallel reporter and chromosome conformation capture assays to identify novel regulatory variants and their target genes related to skin pigmentation in melanocytic cells. We identified 165 SNPs showing strong differential regulatory activities between alleles. Combining CRISPR-mediated genome editing, transcriptome profiling and melanin assays, we identified causal regulatory variants impacting pigmentation near MFSD12/HMG20B, MITF, OCA2, and DDB1/CYB561A3/TMEM138. We identified CYB561A3 as a novel gene regulating pigmentation by impacting genes involved in oxidative phosphorylation and melanogenesis. Our results broaden our understanding of the genetic basis of human skin color diversity and human adaptation. To identify candidate enhancers and regulatory regions in skin pigmentation, we performed CUT&RUN and ATAC assays in  two melanocytic cell lines (MNT-1 and WM88). We used the darkly pigmented MNT-1 cell line because it is widely used for studying skin pigmentation and it has a transcription pattern similar to normal melanocytes. We used the WM88 cell line because the cells are lightly pigmented and may have a different trans-environment (e.g., different levels of transcription factors and open chromatin regions) compared with MNT-1 cells. To identify regulatory regions in MNT-1 cells, we conducted CUT&RUN assays using antibodies against H3K4me3, H3K27ac, MITF and SOX10. We further performed ATAC-seq in both MNT-1 and WM88 cells to identify open chromatin regions. Overall design: Cut&Run, ATAC-seq data in two melanoma cell lines (MNT-1 and WM88).