NKp46‐mediated Dicer1 inactivation results in defective NK‐cell differentiation and effector functions in mice

Abstract

MicroRNAs control developmental pathways and effector functions in immune cells. Previous studies have studied the role of microRNAs in natural killer (NK) cells. However, the mouse models of microRNA depletion used were nonNK-specific and only partially depleting, hampering the interpretation of the data obtained. To clarify the role of microRNAs in murine NK cells, we deleted the RNase III enzyme Dicer1 in NKp46-expressing cells. We observed a drastic decrease in several microRNAs specifically in NK cells. Furthermore, the overall size of the "NK-cell" pool was severely decreased, a phenotype associated with compromised survival. Moreover, performing a broad flow cytometry profiling, we show that Dicer1-deficient NK cells failed to complete their differentiation program. In particular, several integrins were inappropriately expressed in mature NK cells. These defects coincided with decreased response to IL-15, a cytokine responsible for "NK-cell" maturation and survival. In addition, Dicer1 deletion impaired key "NK-cell" functions: target cell killing and production of IFN-γ, leading to defective control of metastasis. Dicer1 deletion thus affects "NK-cell" biology in a cell intrinsic manner at several distinct stages. Keywords: Cytotoxicity Dicer1 IFN-γ MicroRNA NK cellsAdditional supporting information may be found in the online version of this article at the publisher's web-site IntroductionNatural killer (NK) cells are group 1 innate lymphoid cells (ILC1) differentiating in the bone marrow (BM) under the influence of Interleukin (IL)-15 [1]. Following commitment to the "NK-cell" lineage, sequential developmental intermediates, from immature to mature, can be defined on the basis of surface expression of Correspondence: Dr. Antoine Marçais e-mail: antoine.marcais@inserm.fr the tumor necrosis factor (TNF) superfamily member CD27 and the integrin CD11b: CD11b lo CD27 hi NK cells (hereafter referred to as "CD11b lo "), CD11b hi CD27 hi (double positive or "DP"), and CD11b hi CD27 lo ("CD27 lo ") [2,3]. In addition, NK cells lose their capacity to proliferate upon maturation, acquire "NK-cell" receptors as well as cytotoxic arsenal, and modify their trafficking machinery to reach peripheral organs where they exert their role of innate sentinels [4]. They have indeed the capacity to kill cells recognized as targets and to produce IFN-γ upon activation, two functions responsible for their role in the defense against intracellular pathogens and in the immunosurveillance of cancer [5]. This C 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim www.eji-journal.eu Eur. J. Immunol. 2016. 46: 1902-1911 capacity is potentiated by preexposure to IL-15, a process involving the mTOR pathway and granzyme B synthesis [6,7]. Similarly, cytokine stimulation, in particular IL-12/18, triggers secretion of IFN-γ, a property essential to fight intracellular pathogens [1]. Several of these processes might be posttranscriptionally controlled. MicroRNAs are small, noncoding RNAs regulating posttranscriptional gene expression. They are ...

NK Cell Development in Times of Innate Lymphoid Cell Diversity

“…Apart from the regulation of gene expression on the transcriptional level, another epigenetic mechanism is required for the proper development of ILC1s and the adequate maturation of NK cells. Available data implicate small noncoding RNA molecules (221)(222)(223)(224)(225)(226), such as microRNAs (miRs), to regulate posttranscriptional gene expression by binding to the 3 ′ untranslated region (UTR) of mRNAs and inducing either suppression or mRNA translation or its degradation (227). Deletion of the RNase III enzyme Dicer-1, an enzyme required for the generation of single-stranded 20-25 bp long non-coding RNA molecules, in NKp46-expressing cells revealed the role of miRs in murine NK cells and ILC1s (223).…”

“…Available data implicate small non-coding RNA molecules ( 221 – 226 ), such as microRNAs (miRs), to regulate posttranscriptional gene expression by binding to the 3′ untranslated region (UTR) of mRNAs and inducing either suppression or mRNA translation or its degradation ( 227 ). Deletion of the RNase III enzyme Dicer-1, an enzyme required for the generation of single-stranded 20–25 bp long non-coding RNA molecules, in NKp46-expressing cells revealed the role of miRs in murine NK cells and ILC1s ( 223 ). The number of NK1.1 + cells in the organs of Dicer-1 mutant mice was affected, along with the impaired maturation of NK cells.…”

Regulation of Murine Natural Killer Cell Development

“…Recent studies have shown that miRs are also important for NK cell development and function. Using a Dicer1-deficient mouse model that abrogates miR biogenesis in NK cells, Degouve et al ( 72 ). showed that a 10-fold global reduction in miR expression resulted in reduced NK cell numbers, aberrant NK cell maturation, along with attenuated IFN-γ production and cytotoxicity against target cells.…”

“…showed that a 10-fold global reduction in miR expression resulted in reduced NK cell numbers, aberrant NK cell maturation, along with attenuated IFN-γ production and cytotoxicity against target cells. Given that IL-15 signaling via the STAT5 and mTOR pathways was significantly affected, it was proposed that miRs regulate NK cell survival by modulating IL-15 sensitivity ( 72 ). Although it remains unclear as to whether NK cell survival is dependent on specific miRs, miR-155 and miR-15/16 are unlikely candidates since mice that are deficient for either miR have normal NK cell numbers ( 73 , 74 ).…”

T‐bet and Eomes govern differentiation and function of mouse and human NK cells and ILC1

“…The precise interplay between cytokines, mTOR and T‐box factors in NK cells remains however to be fully elucidated. Subtle variations in T‐bet/Eomes ratios may also implicate microRNAs that have a strong impact on NK cell maturation .…”