-acting mutation affecting transcription is underlying the within-feather pigmentation pattern in chickens.

() is a mutation in chickens that extends black (eumelanin) pigmentation in normally brown or red (pheomelanin) areas, thus affecting multiple within-feather patterns [J. W. Moore, J. R. Smyth Jr, 62, 215-219 (1971)]. In the present study, linkage mapping using a back-cross between Dark Cornish (/) and Partridge Plymouth Rock ( ) chickens assigned to an 820-kb region on chromosome 1. Identity-by-descent mapping, via whole-genome sequencing and diagnostic tests using a diverse set of chickens, refined the localization to the genomic region harboring encoding gap-junction protein 5 (alias connexin 40) previously associated with pigmentation patterns in zebrafish. An insertion/deletion polymorphism located in the vicinity of the promoter region was identified as the candidate causal mutation. Four different transcripts were found to be expressed in feather follicles and at least two showed differential expression between genotypes. The results showed that constitutes a -acting regulatory mutation affecting expression. A recent study established the ( locus and the interaction between the MC1R receptor and its antagonist agouti-signaling protein as the primary mechanism underlying variation in within-feather pigmentation patterns in chickens. The present study advances understanding the mechanisms underlying variation in plumage color in birds because it demonstrates that the activity of can modulate the periodic pigmentation patterns within individual feathers.