Transporter that mediates the import of cysteine into melanosomes, thereby regulating skin pigmentation (PubMed:33208952). In melanosomes, cysteine import is required both for normal levels of cystine, the oxidized dimer of cysteine, and provide cysteine for the production of the cysteinyldopas used in pheomelanin synthesis, thereby regulating skin pigmentation (PubMed:33208952). Also catalyzes import of cysteine into lysosomes in non-pigmented cells (PubMed:33208952). L-cysteine(in) = L-cysteine(out) Widely expressed, with high expression in primary melanocytes. Genetic variants in MFSD12 cause skin pigmentation variation (PubMed:29025994, PubMed:30664655). Skin pigmentation is among the most visible examples of human phenotypic variation, with a broad normal range that is subject to substantial geographic stratification (PubMed:29025994, PubMed:30664655). In the case of skin, individuals tend to have lighter pigmentation with increasing distance from the equator (PubMed:29025994, PubMed:30664655). His-192 is commonly found in East Asians and Native Americans only, and significantly correlates with lower solar radiation intensity in East Asia (PubMed:30664655). Belongs to the major facilitator superfamily.