Differential Expression of the Transcription Factor ARID3a in Lupus Patient Hematopoietic Progenitor Cells

Abstract

Although hematopoietic progenitor/stem cells (HPSCs) are used for transplantation, characterization of the multiple subsets within this population in man has lagged behind similar studies in mice. We found that expression of the DNA-binding protein, ARID3a, in mouse stem cells was important for normal development of hematopoietic lineages; however, progenitors expressing ARID3a in man have not been defined. We previously showed increased numbers of ARID3a+ B cells in nearly half of systemic lupus erythematosus (SLE) patients, and that total numbers of ARID3a+ B cells were associated with increased disease severity. Because expression of ARID3a in those SLE patients occurred throughout all B cell subsets, we hypothesized that ARID3a expression in patient HSPCs might also be increased relative to expression in healthy controls. Our data now show that ARID3a expression is not limited to any defined subset of HPSCs in either healthy controls or SLE patients. Numbers of ARID3a+ HSPCs in SLE patients were increased over numbers of ARID3a+ cells in healthy controls. While all SLE-derived HPSCs exhibited poor colony formation in vitro compared to controls, SLE HPSCs with high numbers of ARID3a+ cells yielded increased numbers of cells expressing the early progenitor marker, CD34. SLE HPSCs with high numbers of ARID3a+ cells also more readily generated autoantibody producing cells than HPSCs with lower levels of ARID3a in a humanized mouse model. These data reveal new functions for ARID3a in early hematopoiesis and suggest that knowledge regarding ARID3a levels in HPSCs could be informative for applications requiring transplantation of those cells.

The Transcription Factor ARID3a Is Important for In Vitro Differentiation of Human Hematopoietic Progenitors

“…We previously showed that ARID3a was differentially expressed in multiple subsets of adult peripheral blood HSPCs in lupus patients versus healthy controls (16). To better define the normal roles for ARID3a in early hematopoiesis, we assessed expression in multiple hematopoietic subsets of lineage negative, CD34+ cord blood HSPCS as defined by Notta et.…”

“…Using flow cytometry, HSPCs were gated to allow identification of hematopoietic stem cells (HSCs), multi-myeloid progenitors (MMPs), multi-potent progenitors (MPP), and multi-lymphoid progenitors (MLP) (Fig. 1A) (16). Analysis of these subsets for numbers of ARID3a + cells revealed that 74% of HSCs and MMPs expressed ARID3a, while only 43% of MLPs and 20% of MPPs were ARID3a positive (Fig.…”

“…7, legend). While the role of IL-7 signaling on early human hematopoietic progenitors and B lineage development remains controversial, our previous data link IL-7Rα expression with proliferation of HSPCs in vitro (16). Furthermore, the IL7Rα gene shows putative ARID3a binding by ChIP-seq analysis (our unpublished data and data available from the ENCODE group), indicating a potential role for ARID3a in IL7Rα expression.…”

“…It is now possible to evaluate lineage potential of HSPCs using humanized mouse models (16, 57). However, HSPCs are a heterogeneous population of progenitors that express variable levels of ARID3a within those subpopulations.…”

“…Furthermore hematopoietic stem cells were reduced by >90% in those mice, suggesting an important role for Bright/ARID3a in early hematopoiesis (17). Although we recently showed that ARID3a was variably expressed in multiple human hematopoietic subsets in healthy individuals and in lupus patients (16, 21), the functions of ARID3a during normal human hematopoiesis have not been studied.…”