Abstract
Significance The molecular mechanisms underlying pigmentation patterns in animals is to a large extent an unresolved mystery in biology. For example, compared with mammals, birds show a stunning diversity in pigmentation patterns. This study advances the knowledge concerning the mechanisms creating periodic pigmentation patterns in individual feathers. We show that a mutation upstream of GJA5 encoding a gap-junction protein is causing the Melanotic phenotype in domestic chickens. Melanotic affects within-feather pigmentation patterns by enhancing the contrast between dark- and light-colored regions in the feather. The result implies that cell–cell communications between melanocytes and other cells in the feather follicle play a critical role for pattern formation.
Highlights
Birds exhibit a remarkable diversity in plumage color, including the intensity and type of pigmentation as well as presence of carotenoid and porphyrin pigmentation, and structural colors [1]
Several of the within-feather patterns in chickens are caused by the combined effect of variant melanocortin-1 receptor (MC1R) alleles and mutations at other pigmentation loci [1]. One of these is Melanotic (Ml), which enhances feather eumelanization and extends eumelanin into areas containing pheomelanin pigmentation in the wild-type [8]. It contributes to the within-feather patterns single lacing, double lacing (Fig. 1A), and spangling
Demonstrate that Melanotic is caused by an insertion/deletion polymorphism located at the 5′end of the gap junction protein α5 gene (GJA5) encoding connexin 40 and that Melanotic is a cisacting regulatory mutation affecting GJA5 expression
Summary
Birds exhibit a remarkable diversity in plumage color, including the intensity and type of pigmentation (dark eumelanin versus red/yellow pheomelanin) as well as presence of carotenoid and porphyrin pigmentation, and structural colors [1]. Eight major types of within-feather patterns have been described in the domestic chicken: stippling (wild-type), autosomal barring, pencilling, single and double lacing, spangling, mottling, and sex-linked barring [1, 2]. Several genes affecting this phenotypic variation have been identified. Several of the within-feather patterns in chickens are caused by the combined effect of variant MC1R alleles and mutations at other pigmentation loci [1] One of these is Melanotic (Ml), which enhances feather eumelanization and extends eumelanin into areas containing pheomelanin pigmentation in the wild-type [8]. Demonstrate that Melanotic is caused by an insertion/deletion polymorphism located at the 5′end of the gap junction protein α5 gene (GJA5) encoding connexin 40 and that Melanotic is a cisacting regulatory mutation affecting GJA5 expression
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