TGFB1 and melanoma: Consistent with the biological role of TGF-β in controlling LC residency within the epidermis, our analysis demonstrated that loss of TGF-β was associated with a decrease in LC residency in healthy skin and in the MITFhigh state (Fig. 5B), while mutations that directly promoted TGF-β gain of function strongly or indirectly led to TGF-β up-regulation (for example, MAPK gain-of-function mutants) retained LCs in healthy skin and across the melanoma backgrounds (Fig. 5C).