Genetics ofSex-linked yellowin the Syrian Hamster

Abstract

Alternating patches of black and yellow pigment are a ubiquitous feature of mammalian color variation that contributes to camouflage, species recognition, and morphologic diversity. X-linked determinants of this pattern-recognized by variegation in females but not in males-have been described in the domestic cat as Orange, and in the Syrian hamster as Sex-linked yellow (Sly), but are curiously absent from other vertebrate species. Using a comparative genomic approach, we develop molecular markers and a linkage map for the euchromatic region of the Syrian hamster X chromosome that places Sly in a region homologous to the centromere-proximal region of human Xp. Comparison to analogous work carried out for Orange in domestic cats indicates, surprisingly, that the cat and hamster mutations lie in nonhomologous regions of the X chromosome. We also identify the molecular cause of recessively inherited black coat color in hamsters (historically referred to as nonagouti) as a Cys115Tyr mutation in the Agouti gene. Animals doubly mutant for Sly and nonagouti exhibit a Sly phenotype. Our results indicate that Sly represents a melanocortin pathway component that acts similarly to, but is genetically distinct from, Mc1r and that has implications for understanding both the evolutionary history and the mutational mechanisms of pigmenttype switching.

A composite six bp in-frame deletion in the melanocortin 1 receptor (MC1R) gene is associated with the Japanese brindling coat colour in rabbits (Oryctolagus cuniculus)

“…The former breed (named after its coat colour) has the classic mottled phenotype (Figure 2A ) that is similar to the tortoiseshell pattern observed in female cats and female Syrian hamsters. The coat colour in these two species is caused by the Orange and Sex-linked yellow loci, respectively, that are two non-homologous X chromosome loci [ 38 , 39 ]. The coat colour phenotype determined by the rabbit e J allele is also similar to that determined in guinea-pig by the e p (tortoiseshell) allele at the Extension locus described by classical genetic studies [ 40 , 41 ] but not characterized at the molecular level, yet [ 9 ].…”

A Domestic cat X Chromosome Linkage Map and the Sex-LinkedorangeLocus: Mapping oforange, Multiple Origins and Epistasis Overnonagouti

“…Interestingly the candidate region for Sex-linked yellow in the Syrian hamster was mapped in a nonhomologous region, situated between 46 and 54 Mb on the human X chromosome (Alizadeh et al 2009). Additional in situ hybridization data provided by Alizadeh et al, utilizing mouse BAC probes from the conserved syntenic position in the cat orange region, provide further support that the orange loci in the Syrian hamster and the domestic cat are located in nonhomologous regions.…”

Shades of meaning: the pigment‐type switching system as a tool for discovery

“…Outside of the murine system, additional mysteries await explanation: for example, cats and hamsters each have an X‐linked locus that regulates production of black or orange pigment. Animals that are double mutant for sex‐linked orange and a non‐agouti allele are orange, placing sex‐linked orange downstream of agouti in the pigment pathway (Alizadeh et al., 2009; Schmidt‐Kuntzel et al., 2009). Surprisingly, the cat and hamster sex‐linked orange mutations are likely to be in different genes as they map to non‐homologous regions of the X chromosome.…”