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Schlagwörter:
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Zusammenfassung:
Introduction: We identified a new homozygous stop-codon mutation in the COPZ1
gene (p.Q141X) in two siblings with severe neutropenia and neurological devel-
opmental delay. COPZ1 is a member of the coatomer protein complex I (COPI)
regulating intracellular trafficking of proteins. Moreover, the COPI coat complex is
involved in the early secretory pathway, intracellular trafficking, endosome matura-
tion, lipid homeostasis, and autophagy. COPZ1 is ubiquitously expressed, while its
redundant isoform, COPZ2, is not found in the blood and the brain.
Methods: We introduce the stop-codon mutation at p.Q141X in COPZ1 in healthy
donors` cord blood hematopoietic stem cells (HSPCs) and iPSCs via the CRISPR/
Cas9 gene-editing system. We evaluate the functional effect of gene loss on granulo-
cytic differentiation in bulk liquid culture differentiation and colony-forming capac-
ity by CFUs. The same mutation was also introduced in copz1 in zebrafish embryos
to study the effect on fish granulopoiesis. Additionally, COPZ2 was overexpressed
in COPZ1 mutant HSCs to evaluate its effect on granulopoiesis in vitro.
Results: CRISPR/Cas9-mediated introduction of the stop-codon mutation at the
position p.Q141X in COPZ1 in healthy donors` cord blood hematopoietic stem cells
(HSCs) and iPSCs led to defective granulocytic differentiation in vitro.
Copz1 mutant zebrafish embryos produced significantly fewer neutrophils than
their control counterparts. These findings were in line with hyperactivated unfolded
protein response (UPR) and elevated autophagy in the myeloid cell line NB4 after
introducing the truncated mutation in COPZ1. Moreover, COPZ2 overexpression in
COPZ1 mutant HSCs rescued the granulocytes’ maturation arrest in vitro.
Conclusions: COPZ1 is ubiquitously expressed, while its paralogous gene, COPZ2,
is absent in the blood and the brain. Interestingly, the rescue of COPZ1 mutated
HSPCs with COPZ2 corrected the defective granulopoiesis. Thus, we describe a new
severe congenital neutropenia syndrome caused by autosomal recessive COPZ1
mutations with downstream UPR and autophagy activation.
