Functional characterization of PAX5 gene circular products in B-cell development and function 4458

Abstract Description PAX5 is crucial for B-lineage commitment and adaptive immunity. Recently, we identified a novel class of PAX5 products in B cells: circular RNAs (circRNAs). Given PAX5’s central role in B-cell biology, we hypothesized that PAX5 circRNAs (circPAX5) contribute to B-cell development and function. Using deep sequencing of B-cell lines and primary peripheral blood B-lymphocytes, we mapped 10 distinct circPAX5 isoforms comprising various exon and intron combinations from the PAX5 locus. Notably, the most abundant isoform, circPAX5 2-5, encompasses sequences exons 2 to 5. To explore circPAX5 signaling pathways, we isolated circPAX5 complexes from B-cell lines and characterized their co-interacting partners (miRNAs and proteins) via deep sequencing and mass spectrometry. Intriguingly, circPAX5 interacted with distinct signaling partners depending on the B-cell developmental stage. These findings suggest that circPAX5 plays stage-specific roles by engaging unique interaction networks across B-cell subtypes. To assess circPAX5’s phenotypic impact, we conditionally expressed circPAX5 in various B-cell lines. Similarly, we found that circPAX5 silencing altered cellular growth rates in a differentiation state- and subtype-dependent manner. Altogether, we present circPAX5 products as a new layer of signaling networks mediating B-cell biology. The functional elucidation of circPAX5 products may provide new insight to mechanisms supporting B-cell differentiation and immune development. Funding Sources Supported by NSERC-DDG-2020-00005 Topic Categories Hematopoiesis and Immune System Development (HEM)