Cell-cell signaling elicits local Ca2+ transients in melanocyte dendrites and dendritic spine-like structures

Compartmentalized cytoplasmic fluctuations of Ca2+ within dendrites and dendritic spines regulate a variety of neuronal functions. Like some neurons and glia, melanocytes are neural crest derived and possess dendrites (Adameyko et al., 2009; Erickson et al., 1992; Fitzpatrick and Szabo, 1959). Here, we show that primary human melanocytes, when observed in situ have extensive dendritic branches with dendritic spines similar to neurons. When co-cultured with primary human keratinocytes, they have local Ca2+ transients within these spines and within the dendrites. These are elicited by secreted factors from adjacent keratinocytes. Thus other cell types with dendrites are capable of compartmentalized Ca2+ fluctuations in response to cell-cell communication. Furthermore, our observations within intact human skin suggest a more complex communication network between adjacent melanocytes and keratinocytes, and thus a more complex physiology to skin than previous appreciated.