# RNA Editors Sculpt the Transcriptome During Terminal Erythropoiesis

## TL;DR

This study identifies a key RNA editing pathway involved in red blood cell development and shows it affects globin gene switching, which could help treat blood disorders.

## Contribution

The study reveals a conserved post-transcriptional mechanism involving ZCCHC6/DIS3L2 in terminal erythropoiesis and γ-globin regulation.

## Key findings

- Deficiency in Zcchc6 and Dis3l2 leads to reticulocytosis and RNA-rich erythroid precursors in mice.
- Knockout of ZCCHC6 and DIS3L2 in human cells increases γ-globin levels in terminal erythroid cells.
- The ZCCHC6/DIS3L2 pathway plays a conserved role in RNA editing during red blood cell differentiation.

## Abstract

Selective RNA degradation during terminal erythropoiesis results in a globin-rich transcriptome in mature erythrocytes, but the specific RNA decay pathways remain unknown. We found that deficiency of the terminal uridylyl transferase enzyme Zcchc6 and the 3’−5’ exoribonuclease Dis3l2 in mouse models led to fetal and perinatal reticulocytosis, an accumulation of RNA-rich precursors of terminal erythroid cells, suggesting their crucial roles in terminal red cell differentiation. Notably, knockout embryos exhibited persistent high-level expression of Hbb-bh1 globin, the ortholog of human fetal γ-globin. Perturbation of the Zcchc6-Dis3l2 pathway in mice engineered to express the human b-globin locus likewise increased γ-globin levels in fetal erythroid cells, suggesting that globin switching entails post-transcriptional mechanisms of mRNA destabilization in addition to transcriptional down-regulation. We cultured human hematopoietic stem and progenitor cells (HSPCs), performed CRISPR/Cas9-mediated knockout of ZCCHC6 and DIS3L2, and observed accumulation of RNA and elevated γ-globin levels in terminal erythroid cells. Our findings reveal a conserved role for the ZCCHC6/DIS3L2 RNA editors in terminal erythropoiesis and demonstrate a post-transcriptional mechanism for γ-globin gene switching, advancing research into in vitro erythrocyte generation and γ-globin stabilization to ameliorate hemoglobinopathies.