Sequence Variation in the Bovine Lipin-1 Gene (LPIN1) and Its Association with Milk Fat and Protein Contents in New Zealand Holstein-Friesian × Jersey (HF × J)-cross Dairy Cows

SIMPLE SUMMARY: Lipins are a family of proteins involved in lipid metabolism through their phosphatidate phosphatase and transcriptional co-activator activities. Of the three family members identified, lipin-1 is highly upregulated in the bovine mammary gland during lactation, and has been implicated in regulating milk production, albeit with inconsistent results in different breeds of cattle in studies. Accordingly, its role in regulating milk synthesis is not well understood. In this study, we used polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP) analyses to investigate variation in the bovine lipin-1 gene in New Zealand Holstein-Friesian × Jersey-cross dairy cows and found that variation in the sixth coding exon was associated with milk fat percentage and protein percentage. This suggests that lipin-1 regulates the synthesis of milk fat and milk protein. ABSTRACT: Lipin-1 is known to play a regulatory role in tissues that function in lipid metabolism. In dairy cows, the lipin-1 gene (LPIN1) is highly expressed in the mammary gland, but its function in milk production is less understood. In this study, we used PCR-single strand conformation polymorphism analysis to investigate sequence variation in three regions of bovine LPIN1 in New Zealand Holstein-Friesian × Jersey (HF × J)-cross dairy cows, including part of the 5′ non-coding region, the region containing the LPIN1β-spliced exon, and the sixth coding exon that encodes the putative transcriptional activating domain of the protein. No variation was found in the LPIN1β-spliced exon, but two sequence variants containing one single nucleotide polymorphism (SNP) were identified in the 5′ non-coding region and four sequence variants containing four non-synonymous SNPs were identified in the sixth coding exon. Among the three common variants of the sixth coding exon, variant C was found to be associated with an increase in milk fat percentage (presence 4.96 ± 0.034% vs. absence 4.81 ± 0.050%; p = 0.006) and milk protein percentage (presence 4.09 ± 0.017% vs. absence 3.99 ± 0.025%; p = 0.001), but no associations (p > 0.01) were detected for milk yield. These results suggest that variation in LPIN1 affect the synthesis of fat and proteins in milk and has potential as a gene-marker to improve milk production traits.