Endothelin Receptor B2 (EDNRB2) Is Responsible for the Tyrosinase-Independent Recessive White (mow) and Mottled (mo) Plumage Phenotypes in the Chicken

Abstract

A mutation that confers white plumage with black eyes was identified in the Minohiki breed of Japanese native chicken (Gallus gallus domesticus). The white plumage, with a few partially pigmented feathers, was not associated with the tyrosinase gene, and displayed an autosomal recessive mode of inheritance against the pigmented phenotype. All F1 offspring derived from crosses with mottled chickens (mo/mo), which show characteristic pigmented feathers with white tips, had plumage with a mottled-like pattern. This result indicates that the white plumage mutation is a novel allele at the mo locus; we propose the gene symbol mow for this mutant allele. Furthermore, the F1 hybrid between the mow/mow chicken and the panda (s/s) mutant of Japanese quail (Coturnix japonica), whose causative gene is the endothelin receptor B2 (EDNRB2) gene, showed a mow/mow chicken-like plumage, suggesting the possibility that the mutations in parental species are alleles of the same gene, EDNRB2. Nucleotide sequencing of the entire coding region of EDNRB2 revealed a non-synonymous G1008T substitution, which causes Cys244Phe amino acid substitution in exon 5 (which is part of the extracellular loop between the putative fourth and fifth transmembrane domains of EDNRB2) in the mutant chicken. This Cys244Phe mutation was also present in individuals of four Japanese breeds with white plumage. We also identified a non-synonymous substitution leading to Arg332His substitution that was responsible for the mottled (mo/mo) plumage phenotype. These results suggest that the EDN3 (endothelin 3)–EDNRB2 signaling is essential for normal pigmentation in birds, and that the mutations of EDNRB2 may cause defective binding of the protein with endothelins, which interferes with melanocyte differentiation, proliferation, and migration.

A guinea fowl genome assembly provides new evidence on evolution following domestication and selection in galliformes

“…Whereas all wild guinea fowls exhibited a dark skin on the whole body and a regularly spotted plumage with small white spots (Figure S7), all domestic guinea fowls exhibited large patches of white skin on the head, and white or yellow areas on the shanks. In addition, 16 out of 31 birds exhibited large white spots on the belly feathers and several wing feathers were fully white (Figure S8), mimicking the mottled phenotype encountered in chickens carrying an EDNRB2 mutation (Kinoshita et al., ). Interestingly, five of 31 birds exhibited an extremely diluted phenotype from pale grey to full white, where a ghost spotting pattern could be distinguished (Figure S9), mimicking the mo*w mutation of EDNRB2 described in a full‐white Japanese breed of chickens by Kinoshita et al.…”

“…Another possible explanation could just involve selection on pigmentation. Considering that several coding mutations of EDNRB2 have been associated with extended white spots or extremely diluted plumage colour in some breeds of domestic chickens (Kinoshita et al., ), we performed a careful analysis of the pictures available for the guinea fowls sampled in West Africa. Whereas all wild guinea fowls exhibited a dark skin on the whole body and a regularly spotted plumage with small white spots (Figure S7), all domestic guinea fowls exhibited large patches of white skin on the head, and white or yellow areas on the shanks.…”

A gene expression study of dorso-ventrally restricted pigment pattern in adult fins ofNeolamprologus meeli, an African cichlid species

“…The phenotype resembles dorso-ventrally distinct pigment patterns observed not only in fishes but also in evolutionary distant mammalian and avian species (Figs. 1B and 1C) (Metallinos, Bowling & Rine, 1998; Matsushima et al, 2002; Baxter et al, 2004; Miwa et al, 2007; Hauswirth et al, 2012; Andersson et al, 2013; Kinoshita et al, 2014; Li et al, 2015). …”

Genomic amplification of the caprine EDNRA locus might lead to a dose dependent loss of pigmentation

“…EDNRB signaling is required for melanocyte development36. Loss of function variants in EDNRB lead to white spotting phenotypes in humans (OMIM 131244)7 and animals (OMIA 000375-93934; OMIA 001904-9031)89. In humans, different EDNRB variants cause Waardenburg syndrome 4A (OMIM 277580) and Hirschsprung disease (aganglionic megacolon; OMIM 600155)10.…”