Personalized skincare: from molecular basis to clinical and commercial applications

Figures & data

Table 1 Genotypic variations underlying diverse functions associated with the melanogenic pathways in major ethnic groups

Gene	Caucasian	Oriental	Asian	African
AHCY Adenosylhomocysteinase	Higher expression levels in the darkly pigmented melanocytes^Citation81
ASIP Agouti signaling protein: MC1R antagonist; modulates eumelanin versus pheomelanin synthesis^Citation82,Citation83	Allelic diversity. Associated with darker skin color^Citation32,Citation81
BNC2 Bonapartec – Zn finger protein (basonuclin-2)	Allelic diversity^Citation81,Citation84
DCT Dopachrome tautomerase: conversion of dopachrome to DHICA in the eumelanin pathway. Stabilizes the TYR enzyme Increased expression after UV exposure^Citation32	Allelic diversity^Citation32	Intronic polymorphism at high frequency^Citation85,Citation86		Constitutive levels of protein expression are typically higher in African individuals^Citation32
DRD2 Dopamine receptor D2		Allelic diversity, positive selection^Citation85
EDEM2 ER Degradation Enhancing Alpha-Mannosidase-like Protein 2	Higher expression levels in the dark-and moderate-pigmented melanocytes^Citation81
EGFR Epidermal growth factor receptor: essential role in the control of cell growth^Citation87		Allelic diversity^Citation85		Allelic diversity^Citation85
EIF2S2 Eukaryotic translation initiation factor 2 subunit 2	Higher expression levels in the dark- and moderate-pigmented melanocytes^Citation81
EIF6 Eukaryotic translation initiation factor 6	Higher expression levels in the dark- and moderate-pigmented melanocytes^Citation81
EXOC2 Exocyst complex component 2	Correlates with the levels of serum 25(OH) D, impact on vitamin D status and deficiency common in the Caucasian population^Citation88
GGT7 Gamma-glutamyltransferase 7	Higher expression levels in the dark- and moderate-pigmented melanocytes^Citation81
GSS Glutathione synthetase:, GSH biosynthesis; role in the switch between eumelanogenesis and pheomelanogenesis by interacting with tyrosinase and dopaquinone^Citation32	Allelic diversity^Citation81
HERC2 E3 ubiquitin-protein ligase	Allelic diversity^Citation81
IRF4 Interferon regulatory factor-4	SNP strongly associated with skin tanning response in Europeans^Citation89
ITCH E3 ubiquitin-protein ligase Itchy homologue	Higher expression levels in the dark- and moderate-pigmented melanocytes^Citation81
KITLG c-KIT receptor Development and migration of melanocyte lineages^Citation90	Allelic diversity, positive selection^Citation85	Allelic diversity^Citation85		Significant association with higher melanin index in African-American population^Citation32
MAP1LC3A Microtubule-associated protein 1 light chain 3 alpha	Higher expression levels in the dark- and moderate-pigmented melanocytes^Citation81
MC1R Melanocortin receptor 1 Interacts with ligands encoded by POMC (α-MSH and ACTH) and ASIP (Agouti, antagonist)^Citation91,Citation92	Allelic diversity high. Same effects on pigmentation appear at increased frequency with increasing latitude. Associated with fair skin and freckling^Citation32,Citation93,Citation94		Allelic diversity low^Citation95	Allelic diversity low^Citation94
MITF Microphthalmia transcription factor	Correlates with the levels of serum 25(OH) D, impact on vitamin D status and deficiency common in the Caucasian population^Citation88
OCA2 Membrane transporter Critical for maturation, processing and trafficking of tyrosinase to melanosomes^Citation31	Allelic diversity, positive selection^Citation81	Hypofunctional alleles with 70% of the function of the wild-type protein. Lighter skin pigmentation^Citation96,Citation97,Citation98
PROCR Protein C receptor	Higher expression levels in the dark- and moderate-pigmented melanocytes^Citation81
RALY RNA-binding protein	Higher expression levels in the dark- and moderate-pigmented melanocytes^Citation81
SLC24A4 Solute carrier family 24 member 4: membrane transporter; impact on melanosome biogenesis and tyrosinase activity^Citation31,Citation32	Allelic diversity^Citation81
SLC24A5 Solute carrier family 24 member 5: membrane transporter; impact on melanosome biogenesis and tyrosinase activity^Citation31,Citation32	The key skin pigmentation SNP; strong evidence for selection in Europeans^Citation32		Accounts for lighter skin^Citation99
SLC45A2 (MATP) Solute carrier family 45 member 2: membrane transporter; impact on melanosome biogenesis and tyrosinase activity^Citation31,Citation32	Allele strongly associated with olive skin^Citation85		Accounts for differences between darkest and lightest skin reflectance. Mutations that impair gene function (OCA4) are highest in Asian populations^Citation32,Citation99	Allelic diversity^Citation32
TYR Tyrosinase Catalyzes the initial step critical for the rate of melanin production^Citation32	Allelic diversity. Mutations lead to OCA^Citation81 Correlates with the levels of serum 25(OH) D, impact on vitamin D status and deficiency common in the Caucasian population^Citation88		Accounts for differences between darkest and lightest skin reflectance; highly associated with lighter skin color^Citation24	Largely absent^Citation32
TYRP1 Tyrosinase-related protein 1 Stabilization of tyrosinase protein levels and melanosome maturation Increased expression after UV exposure^Citation100	Allelic diversity, positive selection^Citation85 Correlates with the levels of serum 25(OH) D, impact on vitamin D status and deficiency common in the Caucasian population^Citation88	Allelic diversity^Citation86		Constitutive levels of protein expression are typically higher in African individuals^Citation20,Citation100 Mutations (OCA3) frequently associated with red bronze skin phenotype^Citation101
UQCC Ubiquinol–cytochrome c reductase complex	Higher expression levels in the dark- and moderate-pigmented melanocytes^Citation81

Abbreviations: 25(OH) D, 25-hydroxyvitamin D; a-MSH, α-melanocyte stimulating hormone; ACTH, adrenocorticotropic hormone; ASIP, agouti signaling protein; DCT, dopachrome tautomerase; GSH, glutathione; MC1R, melanocortin receptor 1; OCA, oculocutaneous albinism; POMC, pro-opiomelanocortin; SNP, single-nucleotide polymorphism; TYR, tyrosinase; UV, ultraviolet.

Figure 1 Representative differences within the epidermis and dermis among four ethnic skin types and the age-related changes typical for the traits sensitive to environmental damage.

Abbreviation: TEWL, transepidermal water loss.

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