microRNAs have recently emerged as master regulators of gene expression during development and cell differentiation. Although profound changes in gene expression also occur during antigen-induced T cell differentiation, the role of miRNAs in the process is not known. We compared the miRNA expression profiles between antigen-specific na  ve, effector and memory @entity405 + T cells using 3 different methods--small RNA cloning, miRNA microarray analysis and real-time PCR. Although many miRNAs were expressed in all the T cell subsets, the frequency of 7 miRNAs ( @entity15743 , @entity10017 , @entity43280 -3p, @entity43280 -5p, @entity6529 , @entity27437 and let-7f) alone accounted for approximately 60% of all miRNAs, and their expression was several fold higher than the other expressed miRNAs. Global downregulation of miRNAs (including 6/7 dominantly expressed miRNAs) was observed in effector T cells compared to na  ve cells and the miRNA expression levels tended to come back up in memory T cells. However, a few miRNAs, notably @entity10017 were higher in effector and memory T cells compared to na  ve T cells. These results suggest that concomitant with profound changes in gene expression, miRNA profile also changes dynamically during T cell differentiation. Sequence analysis of the cloned mature miRNAs revealed an extensive degree of end polymorphism. While 3'end polymorphisms dominated, heterogeneity at both ends, resembling @entity10404 /dicer processing shift was also seen in @entity43280 , suggesting a possible novel mechanism to generate new miRNA and/or to diversify miRNA target selection. Overall, our results suggest that dynamic changes in the expression of miRNAs may be important for the regulation of gene expression during antigen-induced T cell differentiation. Our study also suggests possible novel mechanisms for miRNA biogenesis and function.

miRNA profiling of na  ve, effector and memory XXXX T cells.

@entity27437 :: ('406949', 'Gene') :: ['miR-15b'] @entity10404 :: ('29102', 'Gene') :: ['drosha'] @entity15743 :: ('51573', 'Gene') :: ['miR-16'] @entity10017 :: ('406991', 'Gene') :: ['miR-21'] @entity6529 :: ('406942', 'Gene') :: ['miR-150'] @entity43280 :: ('406934', 'Gene') :: ['miR-142'] @entity405 :: ('925', 'Gene') :: ['CD8']
@entity405 :: (925,Gene) :: ['CD8']
