Overexpression of miR-155 causes expansion, arrest in terminal differentiation and functional activation of mouse natural killer cells

PRDM1/BLIMP1 is commonly inactivated in anaplastic large T-cell lymphoma

The commonest lesions in anaplastic large cell lymphomas are losses at 17p13 and at 6q21, concomitant in up to one-quarter of the cases. PRDM1 (BLIMP1) gene (6q21) is inactivated by multiple mechanisms and acts as a tumor suppressor gene in anaplastic large B-cell lymphoma.

Transgenic expression of microRNA-185 causes a developmental arrest of T cells by targeting multiple genes including Mzb1

miR-185 is a microRNA (miR) that targets Bruton's tyrosine kinase in B cells, with reductions in miR-185 linked to B cell autoantibody production. In hippocampal neurons, miR-185 targets both sarcoplasmic/endoplasmic reticulum calcium ATPase 2 and a novel Golgi inhibitor. This miR is haploinsufficient in 90-95% of individuals with chromosome 22q11.2 deletion syndrome, patients who can present with immune, cardiac, and parathyroid problems, learning disorders, and a high incidence of schizophrenia in adults. The reduced levels of miR-185 in neurons cause presynaptic neurotransmitter release. Many of the 22q11.2 deletion syndrome patients have a thymic hypoplasia, which results in a peripheral T cell lymphopenia and unusual T helper cell skewing. The molecular targets of miR-185 in thymocytes are unknown. Using an miR-185 T cell transgenic approach, increasing levels of miR-185 attenuated T cell development at the T cell receptor β (TCRβ) selection checkpoint and during positive selection. This caused a peripheral T cell lymphopenia. Mzb1, Nfatc3, and Camk4 were identified as novel miR-185 targets. Elevations in miR-185 enhanced TCR-dependent intracellular calcium levels, whereas a knockdown of miR-185 diminished these calcium responses. These effects concur with reductions in Mzb1, an endoplasmic reticulum calcium regulator. Consistent with their haploinsufficiency of miR-185, Mzb1 levels were elevated in thymocyte extracts from several 22q11.2 deletion syndrome patients. Our findings indicate that miR-185 regulates T cell development through its targeting of several mRNAs including Mzb1.

MicroRNAs: Essential players in the regulation of inflammation

Regulation of inflammatory responses is ensured by coordinated control of gene expression in participating immune system and tissue cells. One group of gene expression regulators, the functions of which have recently been started to be uncovered in relation to any type of inflammatory condition, is a class of short single-stranded RNA molecules termed microRNAs (miRNAs). miRNAs function together with partner proteins and mainly cause gene silencing through degradation of target mRNAs or inhibition of translation. A particular miRNA can have hundreds of target genes, and thereby miRNAs together influence the expression of a large proportion of proteins. The role of miRNAs in the immune system has been extensively studied since the discovery of miRNAs in mammalian cells approximately 10 years ago. The purpose of the current review is to provide an overview on the functions of miRNAs in the regulation of inflammation, with a specific focus on the mechanisms of allergic inflammation. Because recent studies clearly demonstrate the presence of extracellular miRNAs in body fluids and propose the involvement of miRNAs in cell-cell communication, we will also highlight findings about functions of extracellular miRNAs. The possible use of miRNAs as biomarkers, as well as miRNA-related novel treatment modalities, might open a new future for the diagnosis and treatment of many inflammatory conditions, including allergic diseases.