Beck, L. | Search bioRxiv

bioRxiv2025

Characterization of an immunodeficiency-associated EZH2 variant

Regulation of gene expression is central to the development of immune cells and their ability to respond to infection. As part of a clinical evaluation, we identified two sisters with recurrent infections, hypogammaglobulinemia, and memory B cell deficiency, diagnosed as common variable immunodeficiency. Whole exome sequencing identified a heterozygous variant (Leu50Ser, L50S) in a conserved region of EZH2, the catalytic subunit of the epigenetic gene repressor Polycomb Repressive Complex 2 (PRC2). EZH2-catalyzed histone H3 lysine 27 methylation (H3K27me) in bulk was not overall significantly disrupted by this variant, in patient samples or cell lines expressing EZH2-L50S. EZH2-L50S protein is expressed similar to wild-type and can form PRC2. However, we find that specific genomic regions that normally have high wild-type levels of H3K27me3 are deficient in the L50S context, particularly around gene promoters. EZH2-L50S is still recruited to these sites, but is not as active. Using recombinant purified PRC2, we determine that L50S affects methylation of nucleosomes and disrupts allosteric stimulation that normally amplifies H3K27me3, consistent with the location of L50 in the allosteric regulatory region of PRC2. Thus, variation of EZH2 L50, occurring at low frequency in the population may interfere with normal B cell gene expression patterns, contributing to immunodeficiency. This study has implications for genetic variation in PRC2 in the general population.

molecular biology↗

bioRxiv2023

Expression of modified FcγRI enables myeloid cells to elicit robust tumor-specific cytotoxicity

Despite the central role of T cells in tumor immunity, attempts to harness their cytotoxic capacity as a therapy have met limited efficacy, partially as a result of the suppressive microenvironment which limits their migration and activation. In contrast, myeloid cells massively infiltrate tumors and are well adapted to survive these harsh conditions. While they are equipped with cell-killing abilities, they often adopt an immunosuppressive phenotype upon migration to tumors. Therefore, the questions of how to modify their activation programming against cancer, and what signaling cascades should be activated in myeloid cells to elicit their cytotoxicity have remained unclear. Here, we found that activation of IgM-induced signaling in myeloid cells results in secretion of lytic granules and massive tumor cell death. These findings open venues for designing novel immunotherapy by equipping monocytes with chimeric receptors that target tumor antigens and consequently, signal through IgM receptor. Nonetheless, we found that myeloid cells do not express the antibody-derived portion used to recognize the tumor antigen due to the induction of an ER stress response. To overcome this limitation, we designed chimeric receptors that are based on the high-affinity Fc{gamma}RI for IgG. Incubation of macrophages expressing these receptors along with tumor-binding IgG induced massive tumor cell killing and secretion of reactive oxygen species and Granzyme B. Overall, this work highlights the challenges involved in genetically reprogramming the signaling in myeloid cells and provides a framework for endowing myeloid cells with antigen-specific cytotoxicity.

immunology↗