Severe Congenital Neutropenia

Brianna Davis and Daniel Link

Department of Internal Medicine – Bone Marrow Transplant

 Washington University School of Medicine

 

Severe congenital neutropenia (SCN) is a condition characterized by severe chronic neutropenia present at birth with an absolute neutrophil count below 200 cells/mL and accumulation of myelocytes and promyelocytes in the bone marrow due to maturation arrest.   Neutrophils are considered the primary body defense mechanism against infection and therefore neutropenia is considered critical.  One of the fatal complications of SCN is the development of myelodysplastic syndrome (MDS) or acute myeloid leukemia (AML).  Treatment for SCN is G-CSF, a growth factor that promotes stem cell differentiation from the pluripotent stem cells. A subset of cases of SCN has mutations in the ELA2 gene encoding neutrophil elastase. Disturbingly, the prevalence of G-CSFR mutations is 40% while on G-CSF therapy.  78% of these patients develop MDS/AML.

 Previous studies in the Link Lab have suggested that the G-CSFR mutation confers a growth advantage at the stem cell level.  They have also hypothized that the Stat5 gene may mediate the effect of G-CSF on the G-CSF receptor (G-CSFR) at the stem cell level and promote leukemogenesis. To validate this hypothesis, two experiments were implemented:  1.) Retroviral transduction of Stat5 -/- fetal liver cells with wild type or mutant G-CSFR 2.)  Characterize their growth and differentiation.  To confirm the expression of G-CSFR we utilized a biotinylation G-CSF flowcytometry based assay.  We validated the expression of G-CSFR primarily in bone marrow cells and later we verified the expression of G-CSFR in Baf cells transduced with wild type G-CSFR and control. We concluded that Baf cells transduced with WT G-CSFR were able to produce functional G-CSFR.  In the near future we will study the effect of G-CSF on transduced Stat5 -/-fetal liver cells with WT or mutant G-CSFR and analyze the outcome.