Expression of Pyruvate Carboxylase mRNA Variants in Liver of Dairy Cattle at Calving

BACKGROUND: Bovine liver expresses six pyruvate carboxylase (PC) transcript variants, bPC5′A, bPC5′B, bPC5′C, bPC5′D, bPC5′E, and bPC5′F, which only differ at the 5′ untranslated region (UTR) and contain a common coding region. The objective of this experiment was to determine the profile and abundance of PC transcripts in bovine liver at calving. METHODOLOGY/PRINCIPAL FINDINGS: A ribonuclease protection assay (RPA) protocol was developed to simplify analysis of these variants and investigate the changes in abundance of each 5′ UTR transcript relative to total PC mRNA. Liver biopsy samples collected from seven cows on +1 d relative to calving were analyzed by RPA to determine the profile in PC 5′ UTR variants. Results show that all six bovine PC 5′ UTR variants are detected at calving. Data indicate that bovine PC 5′ UTR variant A is the most abundant, variants C and E are least abundant and expression of variants B, D and F is intermediate at calving. CONCLUSIONS: This manuscript describes a simplified RPA method that quantifies the abundance of six PC transcripts by using two riboprobes. The lack of uniformity in the pattern of PC 5′ UTR variants at calving suggests an additional complexity for control of bovine PC mRNA expression at calving that may be the result of transcriptional controls, variation in mRNA processing, or a combination of these processes.