Differentiation of B cell precursors into antibody-secreting B lymphocytes is a multi-stage process, and dysregulation of this intricate differentiation pathway is implicated in a wide range of immune diseases, from primary immunodeficiencies (PIDs) to autoimmune disorders such as systemic lupus erythematosus (SLE). An insufficient understanding of the molecular mechanisms that govern B cell biology is one of the critical barriers preventing development of impactful therapies against these B cell-mediated diseases. Control of gene expression by microRNAs (miRNAs) has recently emerged as a key mechanism that regulates B cell ontogenesis and effector responses. Thus, better insights into how individual miRNAs function in B cells may allow us to create novel, targeted strategies against immune diseases. The focus of this proposal is on miR-142. Using a loss-of-function genetic approach, we have established miR-142 as an essential, cell- intrinsic regulator of B cell physiology. miR-142 plays two contrasting roles in B cells ? it attenuates B cell maturation, while promoting antibody responses. The objective of this proposal is to gain further insights into the role of miR-142 in B cell development and effector functions, and determine its mode of action in B cells. We have identified Wiskott-Aldrich syndrome like (WASL) gene as a bona fide target of miR-142 in B cells. WASL, like its close homolog WAS gene which is frequently mutated in patients with PIDs, encodes a multidomain protein that functions as a signaling hub that coordinates actin polymerization. Actin remodeling is important in the regulation of multiple aspects of B cell biology, including B cell maturation and antibody responses. Thus, our overall hypothesis is that miR-142, in part by targeting WASL, plays a crucial role in the regulation of B cell maturation and B cell effector responses. We will test our central hypothesis with three specific aims.
In Aim 1, we will investigate the role of miR-142 in primary B cell development and define its mode of action. We will characterize B cell maturation defects in miR-142-/- mice, and link them to underlying molecular changes. Experiments proposed in Aim 2 will determine the impact of miR-142 deletion on B cell effector functions. Using mice with a conditional deletion of miR-142 in activated B cells, we will investigate the role of miR-142 in germinal center formation, immunoglobulin class-switching, and differentiation of long-term plasma cells. We will connect any observed defects in the physiology of miR-142-deficient effector B cells with changes in signaling and gene expression patterns. Finally, in Aim 3, we will define the role of WASL in miR- 142-mediated control of B cell maturation and effector responses by epistasis analysis. The proposed research is significant because it will advance our understanding of the post-transcriptional mechanisms that govern B cell development and humoral immune response. Moreover, our work is expected to establish miR-142 and its downstream target WASL as attractive pharmacological targets for treatment of B cell-mediated disorders, including PIDs and SLE.

Public Health Relevance

B cells produce antibodies which are critical for the generation of protective immunity against infections. This proposal is expected to increase our understanding of the molecular mechanisms that regulate B cell development, functions, and antibody production. This research is relevant to public health because it lays the groundwork for developing new therapeutic strategies to prevent and treat autoimmune disorders and primary immunodeficiencies.

National Institute of Health (NIH)
National Institute of Allergy and Infectious Diseases (NIAID)
Research Project (R01)
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Cellular and Molecular Immunology - A Study Section (CMIA)
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Ferguson, Stacy E
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Beckman Research Institute/City of Hope
United States
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Magilnick, Nathaniel; Boldin, Mark P (2018) Molecular Moirai: Long Noncoding RNA Mediators of HSC Fate. Curr Stem Cell Rep 4:158-165
Magilnick, Nathaniel; Reyes, Estefany Y; Wang, Wei-Le et al. (2017) miR-146a-Traf6 regulatory axis controls autoimmunity and myelopoiesis, but is dispensable for hematopoietic stem cell homeostasis and tumor suppression. Proc Natl Acad Sci U S A 114:E7140-E7149