Patients with SCN are characterised by a high risk of myelodysplastic syndrome and acute myeloid leukaemia. Germline mutation in the ELANE gene is the most common cause of SCN, and mutations are dominant in nature, preserving gene expression while altering the structure of the neutrophil elastase protein product, which results in altered protein folding and/or trafficking with excess cell death at the promyelocyte/myelocyte stage of maturation. Recent advances in gene editing technologies have enabled targeted genetic modification of haematopoietic stem cells.
Dr Shuquan Rao (Harvard Medical School, USA) and colleagues postulated that the introduction of premature termination codons by nuclease-mediated frameshift mutations within early exons of ELANE could be a simple therapeutic approach for ELANE-associated SCN. By introducing premature termination codons, the hypothesis was that nonsense-mediated decay of the mutant transcript would ensue, with consequent loss of gene expression, and thereby no longer causing neutrophil precursor cell death and consequent neutropenia.
The researchers employed CRISPR-Cas9 gene editing to target ELANE in primary human CD34+ haematopoietic stem and progenitor cells in in vitro neutrophil maturation culture. The researchers first introduced early indels at exon 2 of ELANE and observed robust nonsense-mediated decay, as hypothesised. Edited cells were fully competent for neutrophil maturation similar to neutral locus targeted control cells. Using 3 human donors, they showed that ELANE exon 2 edited haematopoietic stem and progenitor cells produced similar human bone marrow chimerism as unedited cells in NBSGW recipient mice 16 weeks following infusion. In a translational experiment using CD34+ haematopoietic stem and progenitor cells from 4 ELANE mutant SCN patient donors, it was demonstrated that exon 2 targeting ribonucleoproteins achieves highly efficient editing exceeding 95% indel frequency, trigger ELANE transcript decay, and rescue promyelocyte stage maturation arrest.
The authors then examined naturally occurring SCN-associated frameshifts, which affect late exons of ELANE. Targeting ELANE exon 5 in haematopoietic stem and progenitor cells resulted in robust indels (93.5%) preserving ELANE expression, but, unlike the results from targeting exon 2, it now resulted in cell death at the promyelocyte/myelocyte stages of development, recapitulating an SCN phenotype.
Together, these results support the development of ELANE early exon targeting as a highly efficient universal therapy for ELANE-mutant SCN, feasible with existing gene editing technology. Moreover, with late exon ELANE gene editing Dr Rao and colleagues have developed a robust new model of SCN using primary human haematopoietic stem and progenitor cells that recapitulates neutropenia in vivo.
1. Rao S, et al. Abstract 3, ASH 2019, 7-10 December, Orlando, USA.
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Table of Contents: ASH 2019
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Late-Breaking Abstracts
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Adding daratumumab to carfilzomib/dexamethasone prolongs PFS and OS in R/R MM
Long-term data of ropeginterferon alpha-2b in polycythaemia vera
Anti-CD70 is safe with hypomethylating agents in AML
MRD assessment to guide pre-emptive treatment decisions
Luspatercept effective for myelofibrosis-associated anaemia
Arsenic, ATRA, and ascorbic acid in acute promyelocytic leukaemia maintenance
Updated results ECOG-ACRIN E2906: decitabine maintenance after alloSCT
Sickle Cell Disease
Arginine supplements help against sickle cell disease pain
Abatacept prevents graft-versus-host disease in sickle cell patients after alloSCT
Plenary Scientific Session
HOVON-96: Better outcomes with cyclophosphamide after transplantation
Erythroferrone and skeletal changes associated with thalassaemia
Experimental model for limitations of haematopoietic stem cells propagation
Mosunetuzumab: complete remissions in non-Hodgkin lymphoma
Inclusive Medicine
Socioeconomic disparities and survival in paediatric AML
Oral selinexor/pomalidomide/dexamethasone shows activity in heavily pre-treated multiple myeloma
CAR T-cell therapy successful in older non-Hodgkin’s lymphoma patients
Mild renal impairment in African Americans does not affect OS in AML
ALCYONE: New overall survival results for myeloma
Venous Thromboembolism
Rivaroxaban is safe and effective for paediatric venous thromboembolism
Aspirin plus DOAC is not better than a DOAC alone
20-Year follow-up of imatinib in chronic myeloid leukaemia after failure with interferon
CAR T and Beyond
BCMA-targeted CAR T therapy yields 100% response in relapsed/refractory MM
Anti-BCMA/anti-CD38 in refractory multiple myeloma
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