Massese is an Italian dairy sheep breed characterized by animals with black skin and horns and black or apparent grey hairs.Owing to the presence of these two coat colour types, this breed can be considered an interesting model to evaluate the effectsof coat colour gene polymorphisms on this phenotypic trait. Two main loci have been already shown to affect coat colour in sheep:Agouti and Extension coding for the agouti signalling protein (ASIP) and melanocortin 1 receptor (MC1R) genes, respectively. TheAgouti locus is affected by a large duplication including the ASIP gene that may determine the Agouti white and tan allele (AWt). Other disrupting or partially inactivating mutations have been identified in exon 2 (a deletion of 5 bp, D5; and a deletion of 9 bp, D9) and in exon 4 (g.5172T.A, p.C126S) of the ASIP gene. Three missense mutations in the sheep MC1R gene cause the dominant black ED allele (p.M73K and p.D121N) and the putative recessive e allele (p.R67C). Here, we analysed these ASIP and MC1R mutations in 161 Massese sheep collected from four flocks. The presence of one duplicated copy allele including the ASIPgene was associated with grey coat colour (P59.4E-30). Almost all animals with a duplicated copy allele (37 out of 41) showeduniform apparent grey hair and almost all animals without a duplicated allele (117 out of 120) were completely black. Differentforms of duplicated alleles were identified in Massese sheep including, in almost all cases, copies with exon 2 disrupting orpartially inactivating mutations making these alleles different from the AWt allele. A few exceptions were observed in theassociation between ASIP polymorphisms and coat colour: three grey sheep did not carry any duplicated copy allele and four black animals carried a duplicated copy allele. Of the latter four sheep, two carried the ED allele of the MC1R gene that may be the cause of their black coat colour. The coat colour of all other black animals may be determined by non-functional ASIP alleles(non-agouti alleles, Aa) and in a few cases by the ED Extension allele. At least three frequent ASIP haplotypes ([D5:g.5172T],[N:g.5172A] and [D5:g.5172A]) were detected (organized into six different diplotypes). In conclusion, the results indicated thatcoat colours in the Massese sheep breed are mainly derived by combining ASIP and MC1R mutations.
|Numero di pagine||10|
|Stato di pubblicazione||Published - 2011|
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