Abstract
Background:
SMARCD2 (SWI/SNF-related, matrix-associated, actin-dependent regulator of chromatin, subfamily D, member 2) has recently been shown to have a critical role in granulopoiesis in humans, mice, and zebrafish. Our patient presented with delayed cord separation, failure to thrive, and sepsis. Retrospective whole-exome sequencing confirmed a homozygous splice-site mutation in SMARCD2.
Objective:
We sought to provide the second description of human SMARCD2 deficiency and the first functional analysis of human primary SMARCD2-deficient cells.
Methods:
Heparinized venous blood and bone marrow were collected from the patient after obtaining informed consent. Patient leukocytes and CD34+ cells were then isolated, phenotyped, and assessed functionally.
Results:
Circulating neutrophils appeared phenotypically immature, lacking multilobed nuclei, and neutrophil granules lacked lactoferrin but showed normal levels of myeloperoxidase. Neutrophil oxidative burst was preserved in response to phorbol 12-myristate 13-acetate. Patient bone marrow-derived neutrophils and white blood cells showed a severely impaired chemotactic response. Furthermore, white blood cells showed defective in vitro killing of Staphylococcus aureus, consistent with a specific granule deficiency. Finally, patient bone marrow-derived CD34+ cells showed markedly impaired in vitro expansion and differentiation toward the neutrophil lineage. Before her molecular diagnosis, our patient underwent hematopoietic stem cell transplantation and is well 8 years later.
Conclusions:
This report highlights an important role for SMARCD2 in human myelopoiesis and the curative effect of hematopoietic stem cell transplantation for the hematopoietic features of SMARCD2 deficiency.
Keywords:
CEBPε; Splice-site mutation; chemotaxis; inborn error of immunity; lactoferrin; neutrophil-specific granule deficiency; phagocyte disorder.