Dynamic MicroRNA Gene Transcription and Processing during T Cell Development

Abstract

By disrupting microRNA (miRNA) biogenesis, we previously showed that this pathway is critical for the differentiation and function of T cells. While various cloning studies have shown that many miRNAs are expressed during T cell development, and in a dynamic manner, it was unclear how comprehensive these earlier analyses were. We therefore decided to profile miRNA expression by means of Next Generation Sequencing. Furthermore, we profiled miRNA expression starting from the hematopoietic stem cell. This analysis revealed that miRNA expression during T cell development is extremely dynamic, with 645 miRNAs sequenced, and the expression of some varying by as much as 3 orders of magnitude. Furthermore, changes in precursor processing led to altered mature miRNA sequences. We also analyzed the structures of the primary miRNA transcripts expressed in T cells, and found that many were extremely long. The longest was pri-mir-29b-1/29a at ~168kb. All the long pri-miRNAs also displayed extensive splicing. Our findings indicate that miRNA expression during T cell development is both a highly dynamic and a highly regulated process.

Critical role for miR-181a/b-1 in agonist selection of invariant natural killer T cells

“…Among all miRNAs, miR-181a/b is most prominently expressed in DP thymocytes, in which it constitutes up to 40% of all miRNAs (16,17). We generated mice carrying a targeted deletion in miR- 181a/b-1 (miR-181a/b-1 −/− mice) (Fig.…”

“…γδ T cells do not pass the DP stage during development, and it is a matter of debate whether iIELs are derived from DP thymocytes (26,27). Relative expression of miR-181a/b-1 is highest in DP cells, whereas it is expressed at lower levels in double-negative (DN) cells (17). Therefore, it is conceivable that miR-181a/b-1 selectively controls unconventional T-cell subsets that originate from DP thymocytes, such as iNKT cells.…”

“…miR-181 comprises a family of six miRNAs, which are organized in three clusters (miR-181a/b-1, miR-181a/b-2, miR-181c/d). miR-181a constitutes the most prominently expressed miRNA species in DP thymocytes (16,17) and has been associated with modulating TCR signal strength via targeting serine/threonine as well as tyrosine phosphatases (18). Consequently, elevated expression of miR-181a results in reduced phosphatase activity and increased TCR signal strength.…”

Transgenic Expression of MicroRNA-185 Causes a Developmental Arrest of T Cells by Targeting Multiple Genes Including Mzb1

“…1A). It is expressed in immature thymocytes, mature CD4 ϩ CD8 Ϫ and CD4 Ϫ CD8 ϩ T cells, and B cells (5,9,21,22). To determine whether miR-185 levels impact T cell functions, we utilized a gain-of-function transgenic approach (23) in which the murine primary miR-185 (pri-miR-185) was overexpressed in thymocytes and peripheral T cells (Fig.…”

Functional Role of MicroRNAs in Thymocyte Development

“…It has been reported that overexpression of miR-146a in bone marrow lymphoid progenitor cells might impair the development of hematopoietic stem/progenitor cells, eventually resulting in a decreased number of CD4 + T cells in the peripheral blood [29]. In addition, Kirigin et al [30] found that the expression level of miR-146a was different in thymocytes at different developmental stages of the thymus. Li et al [31], using miR-146a overexpression in a mouse model, found that overexpression of miR-146a could promote T-cell proliferation and reduce T-cell numbers.…”