The colors of horses depends on the presence of melanocytes in special cells that carry pigment located at the base of the hair follicles. Melanin, formed in organelles called malanosomes, is passed from melanocytes to skin cells by cytocrine secretion.
Melanin is formed from the oxidation of tyrosine by tyrosinase.
Absence of this enzyme results in an albino animal. The melanocytes originate from the same part of the embryo and at the same time as the central nervous system. After the brain and spinal cord are formed, the cells that are located at the edge, the Neural Crest Cells, migrate throughout the body to form melanocytes of the skin, the adrenal glands, the dentine of the teeth, some of the bones of the base of the skull and voice box, the cornea of the eye, special sensory cells of the ear, and special components of the involuntary nervous system. One important function of colors is that it shields deeper structures from uv rays, which can cause mutations. Gene W disrupts the development of horse color by affecting the distribution of color in the horse.