GPRASP protein deficiency triggers lymphoprolierative disease by stalling B-cell differentiation

Gprasp1 and Gprasp2 encode proteins that control the stability and cellular trafficking of CXCR4, a master regulator of hematopoiesis whose dynamic regulation is required for appropriate trafficking of B-cells in the germinal center (GC). Here, we report that Gprasp1 and Gprasp2-deficient B-cells accumulate in the GC and show transcriptional abnormalities, affecting the mechanisms controlling Aicda expression and exposing them to excessive somatic hypermutation. Consequently, about 30% of mice transplanted with Gprasp-deficient hematopoietic stem and progenitor cells developed a biologically aggressive and fatal B-cell hyperproliferative disease by 20-50 weeks post-transplant. Histological and molecular profiling reveal that Gprasp1- and Grpasp2-deficient neoplasms morphologically resemble human high-grade B-cell lymphomas of germinal center origin with shared morphologic features of both Burkitt Lymphoma (BL) and Diffuse Large B-Cell Lymphoma (DLBCL), and molecular features consistent with DLBCL, as well as elevated mutational burden and heterogenous transcriptional and mutational signature. Thus, reduced Gprasp1 and Gprasp2 gene expression perturbs B-cell maturation and increases the risk of B-cell neoplasms of germinal center origin. As this model recapitulates the essential features of the heterogenous group of human pediatric, adolescent, and adult hematopoietic malignancies, it could be a powerful tool to interrogate the mechanisms of lymphomagenesis for these cancers.