title: RNA sequencing to study gene expression and single nucleotide polymorphism variation associated with citrate content in cow milk.
abstract: The technological properties of milk have significant importance for the dairy industry. Citrate, a normal constituent of milk, forms one of the main buffer systems that regulate the equilibrium between Ca(2+) and H(+) ions. Higher-than-normal citrate content is associated with poor coagulation properties of milk. To identify the genes responsible for the variation of citrate content in milk in dairy cattle, the metabolic steps involved in citrate and fatty acid synthesis pathways in ruminant mammary tissue using RNA sequencing were studied. Genetic markers that could influence milk citrate content in Holstein cows were used in a marker-trait association study to establish the relationship between 74 single nucleotide polymorphisms (SNP) in 20 candidate genes and citrate content in 250 Holstein cows. This analysis revealed 6 SNP in key metabolic pathway genes [isocitrate dehydrogenase 1 (NADP+), soluble (IDH1); pyruvate dehydrogenase (lipoamide) β (PDHB); pyruvate kinase (PKM2); and solute carrier family 25 (mitochondrial carrier; citrate transporter), member 1 (SLC25A1)] significantly associated with increased milk citrate content. The amount of the phenotypic variation explained by the 6 SNP ranged from 10.1 to 13.7%. Also, genotype-combination analysis revealed the highest phenotypic variation was explained combining IDH1_23211, PDHB_5562, and SLC25A1_4446 genotypes. This specific genotype combination explained 21.3% of the phenotypic variation. The largest citrate associated effect was in the 3' untranslated region of the SLC25A1 gene, which is responsible for the transport of citrate across the mitochondrial inner membrane. This study provides an approach using RNA sequencing, metabolic pathway analysis, and association studies to identify genetic variation in functional target genes determining complex trait phenotypes.
authors: Department of Animal Science, University of California-Davis, One Shields Ave., Davis 95616.
authors: A
authors: A
authors: Cánovas
authors: Department of Animal Science, University of California-Davis, One Shields Ave., Davis 95616.
authors: G
authors: G
authors: Rincón
authors: Department of Animal Science, University of California-Davis, One Shields Ave., Davis 95616.
authors: A
authors: A
authors: Islas-Trejo
authors: Dairy Products Technology Center, Department of Agriculture, California Polytechnic State University, San Luis Obispo 93407.
authors: R
authors: R
authors: Jimenez-Flores
authors: Dairy Products Technology Center, Department of Agriculture, California Polytechnic State University, San Luis Obispo 93407.
authors: A
authors: A
authors: Laubscher
authors: Department of Animal Science, University of California-Davis, One Shields Ave., Davis 95616. Electronic address: jfmedrano@ucdavis.edu.
authors: J F
authors: JF
authors: Medrano
mesh_terms: D000818:Animals; D002417:Cattle / Q000235:genetics*; D019343:Citric Acid / Q000032:analysis*; D005227:Fatty Acids / Q000096:biosynthesis; D005260:Female; D015870:Gene Expression; D005819:Genetic Markers / Q000235:genetics; D014644:Genetic Variation; D005838:Genotype; D008892:Milk / Q000737:chemistry*; D010641:Phenotype; D020641:Polymorphism, Single Nucleotide / Q000235:genetics*; D017423:Sequence Analysis, RNA / Q000662:veterinary*
chemical_list: D005227:Fatty Acids; D005819:Genetic Markers; D019343:Citric Acid