Reverse Genetic Screens Reveal Mechanisms of Transcriptional Regulation in B cell Differentiation

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Presentation Time: 03:15 PM - 04:30 PM
Poster Board Number: B720
Abstract ID: 5946

Presenting Author:
Roy N Mulpur , PhD Candidate at Emory Univ.

Abstract:

Naïve B cells (NBCs) differentiate into effector states such as antibody secreting cells (ASC) and memory B cells (MBC) to provide immunity against pathogens. Yet, the mechanism responsible for programming naïve B cells to adopt a particular cell fate is not fully understood. During differentiation, B cells undergo changes in gene expression and transcription factor networks that are influenced by alterations in the epigenome to correspond to their effector functions. Our previous work shows that NBCs undergo a hierarchy of reprogramming after exposure to T independent (TI) antigens, including an ASC and MBC cell fate bifurcation at division 3-4. To identify factors controlling each cell fate, RNA-seq of ASC and MBC committed B cells revealed 87 differentially expressed transcription factor/epigenetic modifier genes that were targeted in a CRISPR dropout screen. NBCs were transduced with a gRNA library and differentiated into ASCs in-vitro using a T cell Independent (TI) and dependent (TD) like approach in which they were co-cultured with feeder cells expressing CD40L+ BAFF. This screen revealed that Runx1 and the histone variant H1f0 play a role in positive regulation and Msh5 and Arid5a as negative regulators of ASC differentiation in the TI condition. Interestingly Aicda also was shown to be a positive regulator in the TI condition. These hits along with the hits from the TD ASC differentiation screen reveal mechanisms of transcriptional regulation in ASC differentiation.