## 1 Introduction  
To investigate the variability in skin characteristics among individuals, genetic studies of skin aging are currently being conducted. Several GWASs are in progress to assess skin phenotypes, which have identified gene variants associated with pigmentation in _OCA2_, _MC1R_, _ASIP_, _SLC45A2_, _TYR_, _IRF4_, and _BNC2_ that are linked to hyperpigmentation spots and pigmentation characteristics such as skin color [1, 2, 3, 4, 5, 6, 7, 8]. The first variants recognized as affecting pigmentation in animals were _MC1R_ variants, which are also associated with human pigment phenotypes [9], including freckles [6, 10] and sun sensitivity [11, 12].  
In addition, this phenotype contributes to the risk of melanoma, Basal cell carcinoma and Squamous cell carcinoma, and the genes contribute to skin disease risks, in addition to skin phenotypes [13, 14, 15, 16, 17, 18, 19]. _IRF4_, _MC1_, and _SLC45A2_ were identified as significant loci associated with sensitive skin [12], and these genes are also associated with pigmentation [20], melanogenesis [21, 22], and skin-related cancer [23]. Studies have shown that the _EGFR_, _MMP16_ and _COL17A1_ genes are associated with an increased risk of developing wrinkles, in addition to skin pore size [24]. An SNP located proximal to _TGIF1_ is related to sagging eyelids [25], and the _STXBP5L_ locus is related to facial photoaging [26]. An SNP located upstream of the _Patched-1_ gene was identified as being related to stress-induced skin conditions and aging [27], and _Myc_ interacts with skin hydration [28].  
Skin undergoes decreases in moisture, elasticity, and luster due to aging and external factors, resulting in increased wrinkle depth and the hyperpigmentation of blemishes [29]. Previous studies have confirmed similar trends in age-specific skin phenotype measurements. In a previous study, age increased the measured value of wrinkles and slightly increased pigmentation. However, the measured values of moisture and oil contents decreased with age [30].  
Environmental changes and personal life patterns are considered external factors for skin aging [31; 32; 33], and a genetic approach to skin aging is necessary to better understand individual skin characteristics. A recent study reported new genomic loci [34; 35] related to pigmented facial spots in Koreans and identified SNPs associated with melanin, gloss, hydration, wrinkles, and elasticity [29]. However, few studies have investigated the genetic basis of skin phenotypes among Koreans.  
This research team previously performed GWASs of skin characteristics among 1079 Korean subjects and identified 23 genes related to skin characteristics [30]. Five cosmetic phenotypes (wrinkles, moisture content, pigmentation, oil content, and sensitivity) were evaluated. This GWAS identified SNPs in 23 genes for the five skin phenotypes, including two loci associated with both wrinkles and pigmentation (_FCRLS_ and _OCA2_), four wrinkle-related genes (_FCRLS_, _REEP3_, _ADSS_, and _SPTLC1_), five moisture-related genes (_TBS4_, _TRPM3_, _CEMIP2_, _CTSH_, and _TTC39C_), six pigmentation-related genes (_OCA2_, _NCLN_, _TNS1_, _CDC42 BPA_, _HSSST4_, and _UNCX_), five oil-related genes (_SYN2_, _CNDP1_, _GAS6_, _INSR_, and _TNFRSF19_), and the sensitivity-related gene _CREB5_. This present study aimed to determine whether these of 23 previously reported genes could be validated as significant genetic contributors in the new sample of 261 participants.