The epigenetic regulator RINF (CXXC5) maintains SMAD7 expression in human immature erythroid cells and sustains red blood cells expansion

Haematologica. 2022 Jan 1;107(1):268-283. doi: 10.3324/haematol.2020.263558.

Abstract

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.

MeSH terms

  • Adult
  • Animals
  • Cell Cycle
  • DNA-Binding Proteins*
  • Epigenesis, Genetic
  • Humans
  • Leukemia, Myeloid, Acute* / genetics
  • Mice
  • Myelodysplastic Syndromes* / genetics
  • RNA, Messenger
  • Smad7 Protein* / genetics
  • Transcription Factors*

Substances

  • CXXC5 protein, human
  • CXXC5 protein, mouse
  • DNA-Binding Proteins
  • RNA, Messenger
  • SMAD7 protein, human
  • Smad7 Protein
  • Smad7 protein, mouse
  • Transcription Factors

Grant support

Funding: This work was supported by INSERM, Paris-Descartes University, the Ligue Nationale Contre le Cancer (LNCC), the Cochin Institute, and the Laboratory of Excellence GR-EX. AA was supported by LNCC, Société Française d'Hématologie, Fondation pour la Recherche Médicale, and Boehringer Society (travel grant). GM was supported by a fellowship grant from the Ministère de l’Enseignement Supérieur et de la Recherche and Société Française d’Hématologie. ES-B is supported by the National Center for Scientific Research (CNRS) and her team was supported by LNCC and Fondation de France. We are also grateful for support from the French-Norwegian exchange program (Aurora to FP).