The Agouti locus and coat colour in cattle: evaluating ASIP gene variability in local andcosmopolitan cattle breeds.

Coat colour in mammals depends on the relative amount of two types of pigments, eumelanin (black/brown) and phaeomelanin (yellow/red), which are in turn controlled by the Extension (E) and Agouti (A) loci. While E locus encodes the melanocortin-1 receptor (MC1R) gene which is involved in both melanins production, A locus encodes the agouti signaling protein (ASIP) gene that downregulates MC1R activity, resulting in phaeomelanin synthesis. According to the classical epistatic interaction between the E and A loci, wild type alleles at the MC1R gene would allow to express mutated alleles at the A locus. Cattle breeds have a large variability in coat colour. In this study we focused on two autochthonous breeds (Reggiana and Modenese) and a cosmopolitan breed (Holstein) with different coat colour: Reggiana has a classical red coat colour derived by the recessive mutated allele at the MC1R gene; Modenese is characterized by a white-pale grey solid coat colour; and Holstein usually has a spotted white and black coat colour with black derived by a dominant mutated MC1R allele. In this study we characterized the cattle ASIP gene region variability starting from whole genome sequencing (WGS) data obtained from Reggiana (n.50), Modenese (n. 10) and Holstein breeds (n. 50). We identified four insertion/deletions (indels) which might putatively affect ASIP gene regulatory regions. The indels have been also genotyped by end-point PCR and Sanger sequencing in a larger population of the same three breeds and other 10 breeds. The results revealed that the Reggiana and the Italian Holstein breeds were almost completely fixed for alleles that were almost absent in Modenese breed. Variability in the ASIP gene in this breed might be involved in determining its white coat colour. These results provide some first evidence on the elusive role of the ASIP gene in affecting coat colour also in cattle, similarly to what already reported in sheep and goat, where variants in this gene are associated with white coat colours. Acknowledgements The research was funded by the PSRN (Programma di Sviluppo Rurale Nazionale) Dual Breeding 2 (co-funded by the European Agricultural Fund for Rural Development of the European Union and by the MASAF).