Most studies on the genetic basis of human skin pigmentation have focused on people of European ancestry and only a few studies have focused on Asian populations. We investigated the association of skin reflectance and freckling with genetic variants of melanocortin 1 receptor (MC1R) gene in Japanese. DNA samples were obtained from a total of 653 Japanese individuals (ages 19-40 years) residing in Okinawa; skin reflectance was measured using a spectrophotometer and freckling status was determined for each individual. Lightness index (L*) and freckling status were not correlated with age, body mass index or ancestry (Ryukyuan or Main Islanders of Japan). Among the 10 nonsynonymous variants that were identified by direct sequencing of the coding region of MC1R, two variants-R163Q and V92M-with the derived allele frequencies of 78.6 and 5.5%, respectively, were most common. Multiple regression analysis showed that the 163Q allele and the presence of nonsynonymous rare variants (allele frequencies o5%) were significantly associated with an increase in sex-standardized skin lightness (L* of CIELAB (CIE 1976 (L*a*b*) color space)) of the inner upper arm. Relative to the 92V allele, the 92M allele was significantly associated with increased odds of freckling. This is the first study to show an association between the 163Q allele and skin reflectance values; this association indicated that light-toned skin may have been subjected to positive selection in East Asian people.

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BackgroundUnderstanding the whole-body patterns of joint flexibility and their related biological and physical factors contributes not only to clinical assessments but also to the fields of human factors and ergonomics. In this study, ranges of motion (ROMs) at limb and trunk joints of young adults were analysed to understand covariation patterns of different joint motions and to identify factors associated with the variation in ROM.MethodsSeventy-eight healthy volunteers (42 males and 36 females) living on Okinawa Island, Japan, were recruited. Passive ROM was measured at multiple joints through the whole body (31 measurements) including the left and right side limbs and trunk.ResultsComparisons between males and females, dominant and non-dominant sides, and antagonistic motions indicated that body structures influence ROMs. In principal component analysis (PCA) on the ROM data, the first principal component (PC1) represented the sex difference and a similar covariation pattern appeared in the analysis within each sex. Multiple regression analysis showed that this component was associated with sex, age, body fat %, iliospinale height, and leg extension strength.ConclusionsThe present study identified that there is a spectrum of “masculine” and “feminine” types in the whole-body patterns of joint flexibility. This study also suggested that body proportion and composition, muscle mass and strength, and possibly skeletal structures partly explain such patterns. These results would be important to understand individual variation in susceptibility to joint injuries and diseases and in one’s suitable and effective postures and motions.Electronic supplementary materialThe online version of this article (doi:10.1186/s40101-016-0112-8) contains supplementary material, which is available to authorized users.

Degenerative changes of the spine in people of the Okhotsk culture were investigated in adult human skeletal remains from 38 males and 34 females. These findings were then compared with those in materials obtained from the medieval Kamakura period and early-modern peasants on Kumejima, Ryukyu Islands. The three samples clearly showed different patterns. In the Okhotsk series, the cervical spine of each sex had most osteophytes on the vertebral body, while the Kumejima samples had the highest frequency on the lumbar vertebrae. In the Kamakura series, males were most affected on the lower thoracic vertebrae. Moreover, severe osteophytes on the body of the lumbar vertebrae were more frequently seen in the Okhotsk males. Degenerative changes of the articular process of the Okhotsk series were most frequently seen in the lumbar vertebrae and least frequently seen in the cervical vertebrae. This is well contrasted with a high frequency of degenerative changes of cervical apophyseal joint in early-modern Kumejima peasants. The Kamakura series of each sex had generally low frequencies. Severe degenerative changes of apophyseal joint dominantly affected the Okhotsk series. It is inferred that different dynamic loads caused a high frequency of degenerative changes in the corresponding articular parts. For example, because the Okhotsk culture developed a considerable maritime infrastructure, the lifestyle required for sea-mammal hunting and fishing seems to have particularly affected the incidence of severe degenerative changes of the lumbar vertebrae.