Analysis of polymorphisms in the agouti signalling protein (ASIP) and melanocortin 1 receptor (MC1R) genes and association with coat colours in two Pramenka sheep types

Different biogeographical and sociocultural conditions have contributed to develop several West Balkan native sheep populations, most of which are considered as different types of Pramenka sheep. These populations have a wide variety of phenotypes that indirectly indicate a quite high level of genetic variability. Here, we analyzed agouti signalling protein (ASIP) and melanocortin 1 receptor (MC1R) gene polymorphisms in two Pramenka sheep populations (Dubian and Privorian) originated in Bosnia and Herzegovina in which coat colours and colour patterns are not fixed traits and evaluated association between these genes and coat colours of the investigated sheep. All genotyped animals carried only wild type MC1R haplotypes and no association between variability of this gene and coat colour was observed. Association between the absence of duplicated ASIP copy allele and almost complete dark (black/grey) coat colour was highly significant (Fisher exact test: P = 5.872E-09). These results confirmed the role of the Agouti locus in affecting coat colour in sheep. The six animals with complete concordance between absence of duplicated copy allele and extended black/grey coat colour may be homozygous for recessive nonagouti black alleles (A(a)). as indicated in other breeds. Despite the highly significant association observed between absence of duplicated allele and extended dark coat colour in these Pramenka sheep, association was not complete. One Dubian sheep with the same coat colour phenotype was heterozygous with a duplicated and a non duplicated allele. Moreover, spotted black regions were present in all animals carrying at least a duplicated ASIP allele. These results indicated that other genetic factors or mechanisms (additional uncharacterized ASIP alleles, other loci, or epistatic interaction with other genes) might be involved in affecting coat colours (white vs dark) and different spotted patterns in sheep. This study could represent an example of eploitation of native genetic resources to identify and verify association between DNA markers and phenotypic traits. (C) 2012 Elsevier B.V. All rights reserved.