doi:10.1111/j.1365-2052.2009.01909.x Ovine acyl CoA:diacylglycerol acyltransferase 1 – molecular characterization, polymorphisms and association with milk traits M. C. Scata ` *, F. Napolitano*, S. Casu † , A. Carta † , G. De Matteis*, F. Signorelli*, G. Annicchiarico ‡ , G. Catillo* and B. Moioli* *CRA-PCM, via Salaria 31, 00016 Monterotondo, Italy. † AGRIS – Sardegna, Loc. Bonassai, 07040 Olmedo, Italy. ‡ CRA-ZOE, via Napoli, km 12-71020 Foggia, Italy Summary The objective of this work was to characterize the complete coding region of the ovine acyl CoA:diacylglycerol acyltransferase 1 (DGAT1) gene of three Italian sheep breeds: Sarda, Altamurana and Gentile di Puglia. Characterization was accomplished by direct sequencing of 8676 bp of the relevant DNA, including introns and partial 5¢ and 3¢ untranslated regions (UTRs). We detected five novel SNPs; one SNP (g.5553C>T) is located in intron 2, has similar frequencies in the three breeds and showed a negative association with milk fat content. More interesting is an SNP in the 5¢ UTR (g.127C>A), the occurrence of which is rare in the higher milk-fat breeds (Altamurana and Gentile di Puglia); it is located in the core sequence of Sp1, a putative binding site of transcription factors. This SNP showed a significant negative association with milk fat content in the Sarda sheep. Because DGAT1 plays a fundamental role in triacylglycerol synthesis, the novel detected SNP in the 5¢ UTR of the DGAT1 gene might explain, at least partially, the variation of fat content in the milk of Sarda sheep. Keywords dairy sheep, DGAT1 gene, milk traits, single nucleotide polymorphisms. Introduction Acyl CoA:diacylglycerol acyltransferase 1 plays a key role in triacylglycerol synthesis; it catalyses the esterification of a fatty acyl-CoA to the sn-3 position of a diacylglycerol. In cattle, the DGAT1 gene maps to bovine chromosome 14 (BTA 14) and contains a lysine to alanine polymorphism in exon 8 (p.Lys232Ala) that explains 50% of the genetic variation in milk fat percentage (Grisart et al. 2002; Schennink et al. 2007). Barillet et al. (2005), in a popula- tion of Lacaune and Manech sheep breeds, structured according to a granddaughter design, detected a significant QTL for dairy traits at the proximal end of ovine chromo- some 9 (OAR 9), the sheep homolog of BTA14. However, they could not more precisely map the QTL, which had a large confidence interval. The essential role of DGAT1 in milk fat metabolism makes the DGAT gene an interesting candidate for explaining the genetic variation of milk traits in dairy sheep. The whole genomic sequence of the bovine DGAT1 gene is available (Winter et al. 2002), as well as partial sequences of the caprine gene (Angiolillo et al. 2006); in contrast, the sequence of the ovine gene has not been characterized. The main objective of this work was to sequence the whole genomic region of DGAT1 in several sheep of different breeds with the aim of identifying polymorphisms that might be used to evaluate the association of DGAT1 genotypes with milk traits. Materials and methods Animal material and recording of phenotypic traits SNP detection and association analysis of DGAT1 genotypes with milk traits were performed on 108 sheep of three breeds: Altamurana (37), Gentile di Puglia (37) and Sarda (34). Altamurana is a dairy sheep belonging to the subgroup of South European milk-sheep (Pieragostini & Dario 1996). The Altamurana is a local breed from Apulia (South-eastern Italy) and is subject to a rather harsh environment. Gentile di Puglia is an historical triple-purpose Merino-type breed, whose origin may be traced back to the Roman times Address for correspondence B. Moioli, CRA-PCM, via Salaria 31, 00016 Monterotondo, Italy. E-mail: bianca.moioli@entecra.it Accepted for publication 19 March 2009 Ó 2009 The Authors, Journal compilation Ó 2009 Stichting International Foundation for Animal Genetics, Animal Genetics, 40, 737–742 737