Inverted duplication including Endothelin 3 closely related to dermal hyperpigmentation in Silkie chickens

Abstract

The dermal hyperpigmentation phenotype in chickens is controlled by the dominant fibromelanosis allele. One of the ten unique characteristics of Silkie chickens is the fibromelanosis phenotype, which is pigmentation in the dermal layer of the skin and connective tissue. In this study, we found a mutation of fibromelanosis, a genomic rearrangement that included an inverted duplication of endothelin3 (EDN3), is responsible. We show that, as a stimulator of melanoblast proliferation, EDN3 expression was increased in silkie embryos and in both skin and muscle throughout adulthood. EDN3 expression led to an increase in expression of the downstream genes EDNRB2 and TYRP2, and was closely relate with the hyperpigmentation phenotype. We examined eight different Chinese chicken breeds showing hyperpigmentation and conclude that this structural genetic variant exists in all fibromelanosis chicken breeds.

Common Ancestry of theIdLocus: Chromosomal Rearrangement and Polygenic Possibilities

“…The underlying genetic cause of this hyperpigmentation, often referred to as the “black bone phenotype,” was first investigated by Bateson and Punnett using the Silkie BBC breed (Bateson et al, 1911). Genetic crossing experiments identified two independent epistatically interacting factors influencing the degree of pigmentation observed in hybrid crosses between Silkie and White Leghorn chickens (Arora et al, 2011; Dunn and Jull, 1927; Tian et al, 2014a). These two genetic factors responsible for dermal pigmentation are termed “fibromelanosis ( Fm ) locus” and “inhibitor of dermal melanin ( Id ) locus” (Mukherjee et al, 1969; Tixier-Boichard, 2002).…”