St. Vincent's Institute of Medical Research, Fitzroy, Victoria 3065, Australia.
Department of Medicine, Eastern Hill Precinct, Melbourne Medical School, University of Melbourne, Fitzroy, Victoria 3065, Australia.
RNA. 2023 Sep;29(9):1325-1338. doi: 10.1261/rna.079509.122. Epub 2023 Jun 8.
The RNA editing enzyme adenosine deaminase acting on RNA 1 (ADAR1) is an essential regulator of the innate immune response to both cellular and viral double-stranded RNA (dsRNA). Adenosine-to-inosine (A-to-I) editing by ADAR1 modifies the sequence and structure of endogenous dsRNA and masks it from the cytoplasmic dsRNA sensor melanoma differentiation-associated protein 5 (MDA5), preventing innate immune activation. Loss-of-function mutations in are associated with rare autoinflammatory disorders including Aicardi-Goutières syndrome (AGS), defined by a constitutive systemic up-regulation of type I interferon (IFN). The murine gene encodes two protein isoforms with distinct functions: ADAR1p110 is constitutively expressed and localizes to the nucleus, whereas ADAR1p150 is primarily cytoplasmic and is inducible by IFN. Recent studies have demonstrated the critical requirement for ADAR1p150 to suppress innate immune activation by self dsRNAs. However, detailed in vivo characterization of the role of ADAR1p150 during development and in adult mice is lacking. We identified a new ADAR1p150-specific knockout mouse mutant based on a single nucleotide deletion that resulted in the loss of the ADAR1p150 protein without affecting ADAR1p110 expression. The died embryonically at E11.5-E12.5 accompanied by cell death in the fetal liver and an activated IFN response. Somatic loss of ADAR1p150 in adults was lethal and caused rapid hematopoietic failure, demonstrating an ongoing requirement for ADAR1p150 in vivo. The generation and characterization of this mouse model demonstrates the essential role of ADAR1p150 in vivo and provides a new tool for dissecting the functional differences between ADAR1 isoforms and their physiological contributions.
RNA 编辑酶腺苷脱氨酶作用于 RNA1（ADAR1）是细胞内和病毒双链 RNA（dsRNA）固有免疫反应的重要调节剂。ADAR1 的腺苷到肌苷（A-to-I）编辑修饰内源性 dsRNA 的序列和结构，并使其免受细胞质 dsRNA 传感器黑色素瘤分化相关蛋白 5（MDA5）的识别，从而防止固有免疫激活。 的功能丧失突变与罕见的自身炎症性疾病有关，包括 Aicardi-Goutières 综合征（AGS），其特征是固有免疫系统持续上调 I 型干扰素（IFN）。 基因编码两种具有不同功能的蛋白质同工型：ADAR1p110 持续表达并定位于细胞核，而 ADAR1p150 主要存在于细胞质中，并可被 IFN 诱导。最近的研究表明，ADAR1p150 对于抑制自身 dsRNA 引起的固有免疫激活至关重要。然而，ADAR1p150 在发育过程中和成年小鼠中的作用的详细体内特征尚不清楚。我们基于单个核苷酸缺失鉴定了一种新的 ADAR1p150 特异性敲除小鼠突变体，该缺失导致 ADAR1p150 蛋白丢失而不影响 ADAR1p110 的表达。 突变体胚胎在 E11.5-E12.5 时死亡，胎肝细胞死亡和 IFN 反应激活。成年期 ADAR1p150 的体细胞缺失是致命的，并导致快速造血衰竭，这表明 ADAR1p150 在体内的持续需求。该小鼠模型的生成和特征表明 ADAR1p150 在体内的重要作用，并为解析 ADAR1 同工型的功能差异及其生理贡献提供了新的工具。
