Molecular genetics of antibody generation, epigenetics of the antibody response, in vivo antibody response in humanized mice. Mechanisms of immunoglobulin locus activation and targeting, as well as regulation of genome-wide and specific gene expression by epigenetic marks and gut microbiota, in antibody/autoantibody responses and immune memory.
The Casali lab continues to focus on the B cell mechanisms underpinning the maturation of T-dependent (CD40) or T-independent (tolllike receptor) antibody and autoantibody responses, that is, Ig locus class-switch DNA recombination (CSR)/somatic hypermutation (SHM), memory B cell and plasma cell differentiation, and their regulation. Using biochemical and molecular genetic approaches, we elucidated the mechanisms by which AID inserts staggered-end double-strand breaks in S and V(D)J DNA to initiate CSR/SHM, and identified 5’-AGCT-3’ repeats and 14-3-3
adaptors as essential elements in targeting/stabilizing AID to IgH locus. We also defined roles for translesion DNA synthesis polymerases ζ (Rev3) and Ɵ in SHM, a non-enzymatic role for DNA polymerase Rev1 in CSR and a role for the homologous recombination DNA repair Rad52 in alternative non-homologous endjoining (A-NHEJ) of CSR. We have identified HoxC4 as a critical transcription factor in Aicda activation and estrogen-ERs in activation of the HoxC4 promoter and, therefore, AID expression, as modulated by Rab7 small GTPase. Estrogen-activated HoxC4 potentiates AID expression and AID off-targeting, thereby promoting chromosomal translocations,
autoimmunity and lymphomagenesis.
Recently, we have tackled the role of epigenetic modifications and factors, e.g., histone
posttranslational modifications, non-coding RNAs, histone deacetylases (HDACs) and DNA
methylases, in regulating Aicda (AID gene) expression, targeting the CSR/SHM machinery
to the IgH locus, Prdm1 (Blimp1 gene) expression and plasma cell differentiation.
These studies have unveiled important roles for Zn2+-dependent Class I, II, IV HDACs and NAD+-dependent Class III Sirt1 in regulating CSR/SHM and plasma cell differentiation. Also, they indicate that some of such HDACs synergize with epigenetic factors for new outcomes.
As one example, we show critical and concerted roles of the NAD+-Sirt1 histone/nonhistone protein deacetylase with Tet2 DNA demethylase/histone glycosylase, in B cellintrinsic epigenetic odulation of AID and Blimp1 in autoantibody responses. Having perfected the construction of humanized
huNSG/cKitW-41J mice, we can now extend the analysis of such epigenetic modulation human
antibody responses in vivo. Thus, by performing first-class research using cutting-edge
technology and open communication, my laboratory continues to train next generation
scientists to become future leaders in molecular immunology and epigenetics.
