期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2021
卷号：118
期号：41
DOI：10.1073/pnas.2109363118
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：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.
Melanotic (
Ml) 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,
J. Hered. 62, 215–219 (1971)]. In the present study, linkage mapping using a back-cross between Dark Cornish (
Ml/
Ml) and Partridge Plymouth Rock (
ml
+
/ml
+
) chickens assigned
Ml 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
GJA5 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
GJA5 promoter region was identified as the candidate causal mutation. Four different
GJA5 transcripts were found to be expressed in feather follicles and at least two showed differential expression between genotypes. The results showed that
Melanotic constitutes a
cis-acting regulatory mutation affecting
GJA5 expression. A recent study established the
melanocortin-1 receptor (
MC1R) 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
connexin 40/GJA5 can modulate the periodic pigmentation patterns within individual feathers.
