David H. K. Chui

Summary: Sickle cell disease (SCD) is a genetic disorder that affects millions around the world. Enhancement of fetal γ‐globin levels and fetal haemoglobin (HbF) production in SCD patients leads to diminished severity of many clinical features of the disease. We recently identified the transcriptional co‐activator PGC‐1α as a new protein involved in the regulation of the globin genes. Here, we report that upregulation of PGC‐1α by infection with a lentivirus expressing PGC‐1α or by the small‐molecule PGC‐1α agonist ZLN005 in human primary erythroid progenitor CD34⁺ cells induces both fetal γ‐globin mRNA and protein expression as well as the percentage of HbF‐positive cell (F cells) without significantly affecting cell proliferation and differentiation. We further found that the combination of ZLN005 and hydroxyurea (hydroxycarbamide) exhibited an additive effect on the expression of γ‐globin and the generation of F cells from cultured CD34⁺ cells. In addition, ZLN005 induced robust expression of the murine embryonic βh1‐globin gene and to a lesser extent, human γ‐globin gene expression in sickle mice. These findings suggest that activation of PGC‐1α by ZLN005 might provide a new path for modulating HbF levels with potential therapeutic benefit in β‐hemoglobinopathies.

This case report highlights the importance for health care providers to be aware of the αlpha‐thalassemia syndromes, their relevance to clinical care and family counseling, appropriate diagnostic algorithm for definitive diagnosis.

The thalassemias are compelling targets for therapeutic genome editing in part because monoallelic correction of a subset of hematopoietic stem cells (HSCs) would be sufficient for enduring disease amelioration. A primary challenge is the development of efficient repair strategies that are effective in HSCs. Here, we demonstrate that allelic disruption of aberrant splice sites, one of the major classes of thalassemia mutations, is a robust approach to restore gene function. We target the IVS1-110G>A mutation using Cas9 ribonucleoprotein (RNP) and the IVS2-654C>T mutation by Cas12a/Cpf1 RNP in primary CD34+ hematopoietic stem and progenitor cells (HSPCs) from β-thalassemia patients. Each of these nuclease complexes achieves high efficiency and penetrance of therapeutic edits. Erythroid progeny of edited patient HSPCs show reversal of aberrant splicing and restoration of β-globin expression. This strategy could enable correction of a substantial fraction of transfusion-dependent β-thalassemia genotypes with currently available gene-editing technology.

Key Points: iPSC-derived definitive erythroid cells display a globin expression profile corresponding to yolk sac erythromyeloid progenitors. iPSC-derived erythroblasts resemble their postnatal counterparts in terms of gene expression and essential biological processes.

Anemia - edited by Edward J. Benz, Jr. July 2017

Genetic association studies have detected two trans-acting quantitative trait loci (QTL) on chromosomes 2, 6 and one cis-acting QTL on chromosome 11 that were associated with fetal hemoglobin (HbF) levels. In these studies, HbF was expressed as a percentage of total hemoglobin or the number of erythrocytes that contain HbF (F-cells). As the γ -globin chains of HbF are encoded by two non-allelic genes (HBG2, HBG1) that are expressed at different levels we used normalized gene expression and genotype data from The Genotype-Tissue Expression (GTEx)-project to study the effects of cis- and trans-acting HbF expression or eQTL. This allowed us to examine mRNA expression of HBG2 and HBG1individually. In addition to studying eQTL for globin genes we examined genes co-expressed with HBG1 , studied upstream regulators of HBG1 co-expressed genes and performed a correlation analysis between HBG2 and HBG1 and known HbF regulators. Our results suggest differential effect of cis and trans-acting QTL on HBG and HBG1 expression. Trans-acting eQTLs have the same magnitude of effect on the expression of both HBG2 and HBG1 while the sole cis-acting eQTL affected only HBG2 . Furthermore, the analysis of upstream regulators and the correlation analysis suggested that BCL2L1 might be a new potential trans-acting HbF activator. HbF is the major modulator of the phenotype of sickle cell anemia and β thalassemia. Depending on the effect size, modification of trans-acting elements might have a greater impact on HbF levels than cis-acting elements alone.

Hemoglobin S/Black (^Aγδβ)⁰‐thalassemia is a rare sickle cell disease (SCD) variant. On the basis of limited descriptions in the literature, the disease is reported as a mild microcytic anemia with an uncomplicated course. We report the clinical and laboratory data of nine patients whose diagnoses were confirmed by DNA‐based techniques. Despite having mild anemia and high fetal hemoglobin level postinfancy, these patients developed many of the classic complications of SCD, including vaso‐occlusive crisis, acute chest syndrome, avascular necrosis, and cholelithiasis. On the basis of these findings, we recommend that patients with this rare disorder receive specialized hematology care according to SCD guidelines.