In Vivo Screen Identifies Zdhhc2 As A Critical Regulator Of Germinal Center B Cell Differentiation

Germinal center is the central part of the humoral immune response.The differentiation of germinal center B cells is critical for the production of high affinity pathogen-specific antibody.Clonal selection of activated B cells leads to the elimination of low affinity and autoimmune B cells.Repeated and rapid clonal selection greatly improves the antibody affinity and produces high affinity antibodies that help the body effectively eliminate pathogens.Germinal center B cell differentiation requires careful and precise regulation of a large number of molecules.Abnormal regulation leads to immunodeficiency or autoimmune diseases.Therefore,research in genetic regulation of germinal center B cells is of great importance.Many genes that play important roles in germinal center B cell differentiation have been discovered because of mutation or translocation in B cell lymphomas.There are no systemic approach to study regulatory genes of germinal center B cells yet.Due to the complexity of in vivo environment and manipulation,as well as the limitation of the number of germinal center B cells,it is still a problem to screen in vivo for regulatory genes of germinal center B cell differentiation.In this project,we describe a small-scale in vivo screening system with NP-specific B1-8^hi cells and a retroviral sh RNA library targeting 78 candidate genes.Sh RNA library was transduced to B1-8^hi cells by retroviruses and cells were adoptively transferred to wild type mice.Sh RNA abundance were counted to screen strong regulatory genes according to the changes in germinal center B cells after immunization.Zdhhc2,encoding palmitoyl transferase ZDHHC2,highly expressed in germinal center B cells,was identified as a positive regulator of germinal center B cell differentiation.B1-8^hi B cells transduced with Zdhhc2-sh RNA were severely inhibited to differentiate to germinal center B cells in vivo screening system.Further analysis of in vitro differentiated B cell transduced with Zdhhc2-sh RNA showed that Zdhhc2 is critical for proliferation and survival of B cells after CD40L/BAFF/IL21 stimulation,and consequently impacts on the differentiation of germinal center B cells and plasma cells.In summary,these study not only identify Zdhhc2 as a novel regulator of germinal center B cell differentiation but also provide a new approach to study regulators of germinal center B cell differentiation in vivo.