ARPP-16 mRNA is up-regulated in the longissimus muscle of pigs possessing an elevated growth rate.

Selection for increased growth rate in farm and laboratory animals has been used to develop lines with increased body and muscle weights. However, very little is known about the underlying molecular pathways and how their constitutive genes influence this process. In this study, the differential display-reverse transcription PCR (DDRT-PCR) method was employed to identify longissimus muscle genes that are differentially expressed between a line of pigs selected for increased 200-d weight and a randomly selected control line. A 590-bp DDRT-PCR cDNA product was identified and isolated based on its greater abundance in the longissimus muscle of the select line relative to the control line animals. This DDRT-PCR product has 89% identity to the end of the 3'-untranslated region of the bovine 16-kDa cAMP-regulated phosphoprotein cDNA sequence. Reverse transcription PCR (RT-PCR) amplification of the porcine homologue of and subsequent sequencing established that the DDRT-PCR product corresponds to the 3'-end of the porcine duanyu37P-16 transcript. Semiquantitative RT-PCR verified that duanyu37P-16 is up-regulated in the select line and determined that the relative expression level of mRNA is approximately fourfold higher (P < .01) in the select than in the control animals. The deduced amino acid sequence of duanyu37P-16 is highly homologous to the deduced amino acid sequences of bovine, human, and rat and RT-PCR with PCR primers indicated that this gene is expressed in many different porcine tissues. The porcine homologue of the 19-kDa cAMP-regulated phosphoprotein was also amplified by RT-PCR, cloned, and sequenced. The deduced amino acid sequence of differs from duanyu37P-16 only by the addition of 16 N-terminal amino acids. In all tissues studied, mRNA was detected by RT-PCR amplification; however, the relative expression level of duanyu37P-19 mRNA was not differentially expressed between the select and control line animals (P > .05). The fourfold relative increase in duanyu37P-16 mRNA expression in the select line animals indicates that this gene may play an important role in the molecular pathway(s) that regulate postnatal skeletal muscle growth in the pig.

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