What is chocolat plumage in the domestic chicken ?

In an article published in the journal Pigment Cell & Melanoma Research, scientists from the joint research unit, UMR GABI (INRA/AgroParisTech, Jouy-en-Josas) looked for the 'choc' mutation using a sequence capture approach performed on the @BRIDGe core facilities. They rapidly identified a substitution in the coding region of TYRP1, that modified a very conserved amino acid (His214Asn). in parallel, Swedish, American and Chinese scientists performed a genetic linkage analysis that gave the same results. The way the mutation acts was discovered through analysis of the morhpology of melanosomes using transmission electronic microscopsy on the MIMA2 core facilities. The results indicate that the mutation is associated to an anomaly in the melanosome membrane structure: a modification of the color seems to be due to an packaging anomaly of the pigment in this organelle transmitted by the melanocyte to the keratinocyte. Whereas the TYRP1 enzyme was first considered as an actor in eumelanin synthesis, we show here that its role in the structure of melanosome is determinant. A PCR diagnostic test is available for breeders who are interested in this color.
 

Figure Legend: melanosomes from a chicken with black feathers (A: magnification 3000; B magnification 20 000) and a chocolat-color featherd chicken (C magnification 3000; D magnification 20 000).

Article Li JY, Bed'hom B, Marthey S, Valade M, Dureux A, Moroldo M, Pechoux C, Coville JL, Gourichon D, Vieaud A, Dorshorst B, Andersson L, Tixier-Boichard M. 2019. A missense mutation in TYRP1 causes the chocolate plumage color in chicken and alters melanosome structure. Pigment Cell Melanoma Res. 32, 381-39

Contact Michèle Tixier-Boichard: michele.tixier-boichard@inra.fr