Université de Paris, Institut Cochin, INSERM, CNRS, F-75014 Paris, France; Laboratory of Excellence GR-ex, Paris, France; Equipe Labellisée Ligue Nationale Contre le Cancer (LNCC), Paris.
Equipe Labellisée Ligue Nationale Contre le Cancer (LNCC), Paris, France; PSL Research University, Institut Curie Research Center, INSERM U830, Paris, France; SIREDO: Care, Innovation and Research for Children, Adolescents and Young Adults with Cancer, Institut Curie, Paris.
Haematologica. 2022 Jan 1;107(1):268-283. doi: 10.3324/haematol.2020.263558.
The gene CXXC5, encoding a Retinoid-Inducible Nuclear Factor (RINF), is located within a region at 5q31.2 commonly deleted in myelodysplastic syndrome (MDS) and adult acute myeloid leukemia (AML). RINF may act as an epigenetic regulator and has been proposed as a tumor suppressor in hematopoietic malignancies. However, functional studies in normal hematopoiesis are lacking, and its mechanism of action is unknow. Here, we evaluated the consequences of RINF silencing on cytokineinduced erythroid differentiation of human primary CD34+ progenitors. We found that RINF is expressed in immature erythroid cells and that RINF-knockdown accelerated erythropoietin-driven maturation, leading to a significant reduction (~45%) in the number of red blood cells (RBCs), without affecting cell viability. The phenotype induced by RINF-silencing was TGFβ-dependent and mediated by SMAD7, a TGFβ- signaling inhibitor. RINF upregulates SMAD7 expression by direct binding to its promoter and we found a close correlation between RINF and SMAD7 mRNA levels both in CD34+ cells isolated from bone marrow of healthy donors and MDS patients with del(5q). Importantly, RINF knockdown attenuated SMAD7 expression in primary cells and ectopic SMAD7 expression was sufficient to prevent the RINF knockdowndependent erythroid phenotype. Finally, RINF silencing affects 5’-hydroxymethylation of human erythroblasts, in agreement with its recently described role as a Tet2- anchoring platform in mouse. Altogether, our data bring insight into how the epigenetic factor RINF, as a transcriptional regulator of SMAD7, may fine-tune cell sensitivity to TGFβ superfamily cytokines and thus play an important role in both normal and pathological erythropoiesis.
CXXC5 基因，编码视黄酸诱导核因子（RINF），位于 5q31.2 缺失的区域内，该区域在骨髓增生异常综合征（MDS）和成人急性髓系白血病（AML）中常见缺失。RINF 可能作为一种表观遗传调节剂，并被提议作为造血恶性肿瘤的肿瘤抑制因子。然而，在正常造血中缺乏功能研究，其作用机制尚不清楚。在这里，我们评估了 RINF 沉默对人原代 CD34+祖细胞细胞因子诱导的红细胞分化的影响。我们发现，RINF 在未成熟的红细胞中表达，并且 RINF 敲低加速了促红细胞生成素驱动的成熟，导致红细胞（RBC）数量显著减少（~45%），而不影响细胞活力。RINF 沉默诱导的表型依赖于 TGFβ，并由 TGFβ 信号抑制剂 SMAD7 介导。RINF 通过直接结合其启动子而上调 SMAD7 的表达，我们发现 RINF 和 SMAD7 mRNA 水平在来自健康供体骨髓的 CD34+细胞和 MDS 患者的 del(5q)中密切相关。重要的是，RINF 敲低降低了原代细胞中 SMAD7 的表达，并且外源性 SMAD7 表达足以防止 RINF 敲低依赖性的红细胞表型。最后，RINF 沉默影响人类红细胞的 5'-羟甲基化，这与其最近在小鼠中作为 Tet2 锚定平台的描述作用一致。总之，我们的数据提供了关于表观遗传因子 RINF 如何作为 SMAD7 的转录调节剂，可能微调细胞对 TGFβ 超家族细胞因子的敏感性，从而在正常和病理红细胞生成中发挥重要作用的见解。
