Identification of single nucleotide polymorphisms in the ovine acetyl-CoA carboxylase-alpha gene

Identification of Genetic Polymorphisms of PI, PIII, and Exon 53 in the Acetyl-CoA Carboxylase-α (ACACα) Gene and Their Association with Milk Composition Traits of Najdi Sheep

Recently, increasing attention has been paid to sheep milk products, which are high in saturated fatty acids (SFA), and the extent of their impact on human health. This study aimed to identify SNPs for PI, PIII, and Exon 53 in the ACACα gene and their association with the MC and FA profiles in Najdi sheep milk. A total of 76 multiparous Najdi ewes were used, and they were maintained using the same feeding system. Milk and blood samples were collected during the first lactation. A genetic polymorphism analysis identified 20 SNPs: 4 SNPs on PI, 6 SNPs on PIII, and 10 SNPs on Exon 53. In PI, the SNP g.4412G > A was associated (p < 0.05) with palmitic acid (C16:0), palmitoleic acid (16:1 n-7) and linoleic acid (LA), while SNP g.4485C > G was associated with CLA and vaccenic acid (VA) (p < 0.05). Furthermore, in PIII, two SNPs (g.1168A > G and g.1331G > T) were associated with milk protein (p < 0.05), while the SNP g.6860G > C in Exon 53 was associated with milk fat (p < 0.05). SNPs in the Najdi breed have been shown to be strongly related to milk fat and EFA contents. This could support a genetic selection program and the control of milk traits in the Najdi breed of high-quality dairy sheep.

Full-length sequencing and identification of novel polymorphisms in the ACACA gene of Valle del Belice sheep breed

The essential role of the acetyl-CoA carboxylase (ACACA) enzyme in milk fatty acid (FA) synthesis suggests that it may be responsible for the phenotypic variability observed inmilk.Before attempting association analyses between this gene and/or enzyme and phenotypic traits, a study on the genetic variability within this locus is required. The aim of this work was to sequence the entire coding region of ACACA gene in Valle del Belice sheep breed to identify polymorphic sites. A total of 51 coding exons of ACACA gene were sequenced in 32 individuals of Valle del Belice sheep breed. Sequencing analysis and alignment of obtained sequences showed the presence of 23 polymorphic sites. The most polymorphic was exon 53 which showed presence of 12 single-nucleotide polymorphisms (SNPs), ofwhich eightweremissensemutations, caused amino acid changes and therefore may affect protein function or stability causing variation in phenotype. The identified polymorphisms showed high variability of the ACACA gene. Sequences analysis allowed to find six new SNPs in exon 53 (6832C>T; 6835C>A; 6840G>A; 6847G>T; 6852C>T and 6860G>C). A total of 31 haplotypes were inferred. Although this study could not provide association study with production traits, it shows finding of novel SNPs that might be important in future studies and laid the basis for further association analyses needed to evaluate the potential use of these SNPs as genetic markers for fat content and FAs composition in milk of Valle del Belice sheep breed.

Elucidating fish oil-induced milk fat depression in dairy sheep: Milk somatic cell transcriptome analysis

In this study, RNA sequencing was used to obtain a comprehensive profile of the transcriptomic changes occurring in the mammary gland of lactating sheep suffering from fish oil-induced milk fat depression (FO-MFD). The milk somatic cell transcriptome analysis of four control and four FO-MFD ewes generated an average of 42 million paired-end reads per sample. In both conditions, less than 220 genes constitute approximately 89% of the total counts. These genes, which are considered as core genes, were mainly involved in cytoplasmic ribosomal proteins and electron transport chain pathways. In total, 117 genes were upregulated, and 96 genes were downregulated in FO-MFD samples. Functional analysis of the latter indicated a downregulation of genes involved in the SREBP signaling pathway (e.g., ACACA, ACSL, and ACSS) and Gene Ontology terms related to lipid metabolism and lipid biosynthetic processes. Integrated interpretation of upregulated genes indicated enrichment in genes encoding plasma membrane proteins and proteins regulating protein kinase activity. Overall, our results indicate that FO-MFD is associated with the downregulation of key genes involved in the mammary lipogenesis process. In addition, the results also suggest that this syndrome may be related to upregulation of other genes implicated in signal transduction and codification of transcription factors.

The ACACA gene is a potential candidate gene for fat content in sheep milk

No major gene has yet been reported in sheep that explains the variation of milk fat content. The coding region of the acetyl-CoA carboxylase alpha (ACACA) gene, which plays an important role in de novo fatty acid synthesis, had been investigated, but no non-synonymous mutations have been reported. In this study, the genomic regions encoding the three promoters of the ACACA gene were directly sequenced in 264 sheep of three different breeds, and 10 SNPs were identified. Allele frequencies of most SNPs significantly differed (P = 0.05-0.0001) between breeds. The SNPs that potentially altered either gene regulatory elements or putative binding sites of transcription factors were made evident through in silico analysis. The association analysis with milk traits, performed for one SNP of PIII (GenBank AJ292286, g.1330G>T), showed a significant allelic substitution effect (+0.33%, P < 0.0001 and +0.35%, P < 0.01) in the Altamurana and Gentile breeds respectively. Because this SNP was located in the binding site of the paired box protein transcription factors, which was shown to function as an efficient promoter element, and because PIII transcripts are expressed in the mammary gland, the SNP in PIII of the ACACA gene might affect the variation of fat content in sheep milk.