Abstract
Severe congenital
neutropenia (SCN) is often associated with inherited heterozygous point
mutations in ELANE, which encodes neutrophil elastase (NE).
However, a lack of appropriate models to recapitulate SCN has substantially
hampered the understanding of the genetic etiology and pathobiology of this
disease. To this end, we generated both normal and SCN patient–derived induced
pluripotent stem cells (iPSCs), and performed genome editing and differentiation
protocols that recapitulate the major features of granulopoiesis. Pathogenesis
of ELANE point mutations was the result of promyelocyte death
and differentiation arrest, and was associated with NE mislocalization and
activation of the unfolded protein response/ER stress (UPR/ER stress).
Similarly, high-dose G-CSF (or downstream signaling through AKT/BCL2) rescues
the dysgranulopoietic defect in SCN patient–derived iPSCs through
C/EBPβ-dependent emergency granulopoiesis. In contrast, sivelestat, an
NE-specific small-molecule inhibitor, corrected dysgranulopoiesis by restoring
normal intracellular NE localization in primary granules; ameliorating UPR/ER
stress; increasing expression of CEBPA, but not
CEBPB; and promoting promyelocyte survival and
differentiation. Together, these data suggest that SCN disease pathogenesis
includes NE mislocalization, which in turn triggers dysfunctional survival
signaling and UPR/ER stress. This paradigm has the potential to be clinically
exploited to achieve therapeutic responses using lower doses of G-CSF combined
with targeting to correct NE mislocalization.
Authors
Ramesh C. Nayak, Lisa R. Trump, Bruce J. Aronow, Kasiani Myers, Parinda Mehta, Theodosia Kalfa, Ashley M. Wellendorf, C. Alexander Valencia, Patrick J. Paddison, Marshall S. Horwitz, H. Leighton Grimes, Carolyn Lutzko, Jose A. Cancelas
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