Steroidogenic Factor-1 Lineage Origin of Skin Lesions in Carney Complex Syndrome

Carney complex is a rare familial multineoplastic syndrome predisposing to endocrine and nonendocrine tumors due to inactivating mutations of PRKAR1A, leading to perturbations of the cAMP‒protein kinase A signaling pathway. Skin lesions are the most common manifestation of Carney complex, including lentigines, blue nevi, and cutaneous myxomas in unusual locations such as oral and genital mucosa. Unlike endocrine disorders, the pathogenesis of skin lesions remains unexplained. In this study, we show that embryonic invalidation of the Prkar1a gene in steroidogenic factor-1‒expressing cells leads to the development of familial skin pigmentation alterations, reminiscent of those in patients with Carney complex. Immunohistological and molecular analyses, coupled with genetic monitoring of recombinant cell lineages in mouse skin, suggest that familial lentiginosis and myxomas occur in skin areas specifically enriched in dermal melanocytes. In lentigines- and blue nevi‒prone areas from mutant mice and patients, Prkar1a/PRKAR1A invalidation occurs in a subset of dermal fibroblasts capable of inducing, under the influence of protein kinase A signaling, the production of promelanogenic EDN3 and hepatocyte GF signals. Our model strongly suggests that the origin of the typical Carney complex cutaneous lesions is the result of noncell-autonomous promelanogenic activity of a dermal fibroblast population sharing a community of origin with steroidogenic factor-1 lineage.