Predicted miRNA-mRNA-mediated posttranscriptional control associated with differences in cervical and thoracic thymus function.

A secondary cervical thymus (CT) is present in the neck region in about 50% of human and mice. CT in mice is an independent and functional organ, which can be colonized by T lymphocyte progenitors and generate thymocytes that are selected by the T cell receptor repertoire following the positive and negative selection. However, CT and the main thoracic thymus (TT) have been shown in mice to have significant functional differences. In this study, we use transcriptional profiling to compare mRNA or miRNAs expression patterns in murine CT and TT. We used these data to perform functional enrichment of the expression signatures and reconstruction of posttranscriptional miRNA-mRNA interaction networks. For this purpose, we compared the transcriptome profiling of paired RNA samples of whole CTs, TTs and parathyroid gland (PT), which was used as an external group, from Foxn1-GFP;Pth-Cre;R26dTomato transgenic mice that differentially label CT and TT. As expected, CT and TT featured comprehensive transcriptome similarity and this suggests that these organs are subjected to correlated transcriptional control. Nevertheless, significant differences were also observed between TT and CT, characterized by 107 differentially expressed (DE) mRNAs, and in 13 DE miRNAs, that in turn established interactions. These results suggest that functional similarity between TT and CT is reflected in their transcriptional activity and that CT functional uniqueness might be under posttranscriptional control.