Saturday, May 17, 2025
5/17/2025
Genetic determinates of SPI1 expression and activity in human germinal center B cells - PROJECT ABSTRACT Human B cells are exquisitely sensitive to changes in SPI1, a master transcriptional regulator. Loss- and gain-of-function SPI1 gene mutations were recently described as causes of agammaglobulinemia and Waldenström macroglobulinemia. Preliminary data indicates other changes in SPI1 activity/dose may cause additional clinical phenotypes including common variable immunodeficiency (CVID) and autoimmune diseases. The long-range goal of the proposed work is to determine SPI1’s full role in human health and disease(s). Our objective is to establish mechanisms of SPI1 gene regulation in human germinal center B cells and the consequences of dysregulation. The working hypothesis is that SPI1 has a critical role throughout B cell development, including germinal center (GC) B cell maturation, and that the culmination of rare SPI1 coding mutations and common non-coding variants determine disease state. To explore this hypothesis, we propose the following aims: 1) Identify non-coding elements regulating SPI1 gene expression in human GC B cells 2) Delineate effects of coding variants in SPI1 on autoregulation and expression 3) Determine maturational and transcriptional consequences SPI1 LOF and SPI1 GOF mutations to differentiated B cells. The contribution is significant because SPI1’s role in human GC responses is unexplored but is clearly affected in several patient groups carrying SPI1 gene mutations. The proposed work is innovative because we are using only human and human derived cells, including bona fide tonsillar GC B cells for proposed experiments. We are comprehensively investigating the role of coding and non-coding DNA on SPI1 regulation using crystallography, NMR, long-read sequencing, prime editors, base editors, ATAC-, RNA- and ChIP-seq. Finally we are utilizing tonsillar organoids to model the effects of altered SPI1 dose on GC B cell maturation in human lymphoid follicles.
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