The RNA binding protein PTBP1 is necessary for B cell selection in germinal centers

Antibody affinity maturation occurs in germinal centres (GC) where B cells cycle between the light zone (LZ) and the dark zone. In the LZ GC B cells bearing immunoglobulins with the highest affinity for antigen receive positive selection signals from T helper cells that promotes their rapid proliferation. Here we show that the RNA binding protein PTBP1 is necessary for the progression of GC B cells through late S-phase of the cell cycle and for affinity maturation. PTBP1 is required for the proper expression of the c-MYC-dependent gene program induced in GC B cells receiving T cell help and directly regulates the alternative splicing and abundance of transcripts increased during positive selection to promote proliferation.