Possibly relevant human trait(s) and/or gene(s)s (MIM numbers): 266300 (trait) , 155555 (gene)

Mendelian trait/disorder: yes

Mode of inheritance: Autosomal Dominant

Considered a defect: no

Key variant known: yes

Year key variant first reported: 2021

Cross-species summary: horizontal striping pattern on individual feathers

Species-specific description: Schwochow et al. (2021): "There are two distinct types of barring patterns in chicken, autosomal barring and sex-linked barring. While sex-linked barring is adding a white bar on a pigmented background, autosomal barring is adding a black bar on a gold or silver background on individual feathers (Smyth 1990). ... Autosomal barring ... has been suggested to be caused by the combined effect of the three autosomal loci Db, E, and Pg (Andersson et al., 2020; Carefoot, 1985, 1999; Moore & Smyth, 1972) and is the trademark of some chicken breeds such as Fayoumi, Campine, and Westfälische Totleger." The authors "propose that MC1R is the major patterning locus in chickens, i.e., different mutations causing altered regulation of MC1R signaling promote the development of feather patterns in interaction with other loci. One such interacting locus is definitely Dark brown/SOX10, others are melanotic (Ml) and Columbian restriction (Co) for which no underlying causal gene has been reported yet ... . Furthermore, it is possible that regulatory mutations affecting MC1R expression also contribute to the complex inheritance of within-feather patterns in chicken as previously suggested (Ling et al., 2003)" (Schwochow et al., 2021). The study by Schwochow et al.(2021) "provides strong evidence against the previous assumption that a Patterning locus on chromosome 1 has a predominant role for the presence/absence of within-feather patterns in chicken (Smyth, 1990)."

Mapping: Schwochow et al. (2021) "generated an informative backcross involving the Fayoumi breed showing autosomal barring ... and an inbred line of Light Brown Leghorn (LBL) showing no feather pattern and assumed to be wild-type at all the major loci known to influence plumage color. We used pooled sequencing to map the loci affecting feather pigmentation patterns. Our data show that the major locus controlling the segregation of autosomal barring in this cross is located at the distal end of chromosome 11 where the E/MC1R locus is located. We also show that Db [Dark brown, caused by a deletion upstream of SOX10] is not required for autosomal barring but that it affects the manifestation of this phenotype, and we did not find any evidence for the segregation at the proposed Pg locus [Patterning]."

Molecular basis: Schwochow et al. (2021) "show that the autosomal barring phenotype co-segregates with a missense mutation L133Q [E*R(Fay) allele] in the melanocortin 1 receptor (MC1R) gene. ... genotyping data ... further revealed an incomplete association between the Db allele at SOX10 and autosomal barring, which suggests that Db is not required to form the pattern but makes it more pronounced and easier to phenotype. There may be a third locus segregating in our cross, which is responsible for the red belly phenotype only present in males."

Breeds: Campine, Fayoumi, Westfälische Totleger.

Associated gene: