[Cloning and expression analysis of chicken circular transcript of insulin degrading enzyme gene]

Insulin-degrading enzyme (IDE) is a highly conserved metallopeptidase that functions in the catabolism of bioactive peptides. In our previous study, we identified a putative circular transcript in that chicken insulin-degrading enzyme (IDE) gene through analyzing a high throughput sequencing result. Here we set to confirm the circular transcript of IDE (circIDE) and explore its expression regularity in normal barred Plymouth chicken. The circIDE was confirmed by PCR amplification and sequencing. The circular structure of circIDE was determined by RNase R processing and reverse transcription experiments. Then we analyzed the spatiotemporal expression pattern of circIDE and IDE mRNA and compared the differential expression of circIDE and IDE mRNA in the normal barred Plymouth chicken and the dwarf ones. The results showed that the full length of chicken circIDE was 1332 nt, divided form exon 2-11 of the IDE gene. RNase R tolerance analysis showed that chicken circIDE had the general characteristics of circular molecule, and was highly resistant to RNase R. The random primers had higher transcription efficiency than the oligo-d(T)₁₈ primers, confirming that circIDE is a circular structured molecule without poly(A). circIDE was highly expressed in the liver and heart tissues but less in the muscle tissues of leg and breast in normal chickens at the age of 1 and 12 weeks. The expression profile of circIDE in liver tissue showed that circIDE level was lower in1 to 6 weeks and then became higher after 8 weeks of age. The expression of circIDE in liver tissue was significantly higher in normal chicken than that in dwarf barred Plymouth chicken (P<0.05). This study confirmed a circIDE strucutre in chicken IDE gene and uncovered its expression regularity. We demonstrated that the expression level of circIDE in the liver tissue was higher in normal barred Plymouth chicken compared to dwarf species. This study paves the way for further understanding the biological function of chicken circIDE, including its roles in regulating chicken growth and development.