Coloration in Equine: Overview of Candidate Genes Associated with Coat Color Phenotypes

Variation in coat color among equids has attracted significant interest in genetics and breeding research. The range of colors is primarily determined by the type, concentration, and distribution of melanin pigments, with the balance between eumelanin and pheomelanin influenced by numerous genetic factors. Advances in genomic and sequencing technologies have enabled the identification of several candidate genes that influence coat color, thereby clarifying the genetic basis of these diverse phenotypes. In this review, we concisely categorize coat coloration in horses and donkeys, focusing on the biosynthesis and types of melanin involved in pigmentation. Moreover, we highlight the regulatory roles of some key candidate genes, such as MC1R, TYR, MITF, ASIP, and KIT, in coat color variation. Moreover, the review explores how coat color relates to selective breeding and specific equine diseases, offering valuable insights for developing breeding strategies that enhance both the esthetic and health aspects of equine species.

Evaluation of native canine skin color by smartphone-based dermatoscopy

BACKGROUND

Human skin color, predominantly determined by the chromophores of melanin, hemoglobin, and exogenous carotenoids, is often measured to serve various medical and cosmetic applications. Although colorimetry has been used to evaluate the skin erythema in allergic dogs, the native canine skin color remains unknown.

METHODS

We measured the skin color in 101 healthy dogs using a calibrated optical system with a smartphone and a mobile dermatoscope DermLite DL1. The results were retrieved in the CIELAB color system and compared to the human color ranges.

RESULTS

The lightness (L*) of canine skin ranged from 28.5 to 78.3, which is slightly broader than that of human skin. There was a difference of 3.9 in redness (a*) between canine and human skin, but this variation could be attributed to the similarly valued colorimetric error of the optical system. Nonetheless, the skin yellowness was significantly different for dogs and humans (respective median b* of 12.3 versus 16.6, p < 0.01). This difference might be due to canids not being able to accumulate typically yellowish carotenoids. Furthermore, the native canine skin color did not exhibit a typical dependence between the coordinates of lightness (L*) and yellowness (b*), known as the individual typology angle, °ITA.

CONCLUSION

We reported the first dataset of the native canine skin color in the CIELAB color space. We discovered a similarity in skin lightness and a difference in skin yellowness. However, further studies are needed for a more precise comparison of skin redness.