Regulation of AID expression in the immune response

Abstract

The B cell–specific enzyme activation-induced cytidine deaminase (AID) has been shown to be essential for isotype switching and affinity maturation of antibody genes during the immune response. Conversely, AID activity has also been linked to autoimmunity and tumorigenesis. Determining how AID expression is regulated in vivo is therefore central to understanding its role in health and disease. Here we use phylogenetic footprinting and high-resolution histone acetylation mapping to accurately demarcate AID gene regulatory boundaries. Based on this strategy, we identify a novel, positive regulatory element required for AID transcription. Furthermore, we generate two AID indicator mouse strains using bacterial artificial chromosomes that faithfully recapitulate endogenous AID expression. The first strain uses a green fluorescent protein reporter to identify B cells that actively express AID during the immune response. In the second strain, AID transcription affects the permanent expression of a yellow fluorescent protein reporter in post–germinal center and terminally differentiated lymphocytes. We demonstrate the usefulness of these novel strains by resolving recent contradictory observations on AID expression during B cell ontogeny.

Separation of Function between Isotype Switching and Affinity Maturation In Vivo during Acute Immune Responses and Circulating Autoantibodies in UNG-Deficient Mice

“…This is most likely due to the impairment in CSR caused by UNG deficiency (see later), leading to persistence of IgM + cells in the germinal center reaction to accumulate SHM, which can be selected before isotype switching has occurred. We could confirm that the spleen of Ung 2/2 mice contained more IgM + AID + cells after immunization than the controls by using an AID-GFP reporter mouse that allows identifying AID + germinal center cells in response to immunization (23). Indeed, the ratio of IgM + to IgM 2 cells in the AID + B cell population was inverted in Ung 2/2 mice compared with controls (Fig.…”

“…RNA was extracted using RNeasymicro kit (Qiagen) and cDNA produced using Protoscript kit (Biolabs). The suitability of AID-GFP expression in these mice to identify germinal center B cells has been established (23). PCRs were performed on cDNA using oligonucleotides OJ794 59-TCTTCTTGGCAGCAACAG-39, priming at the leader region of VH186.2 and OJ795 59-CCAGATTCTTATCAGACAGGG-39 priming at the IgH Cm1 for 35 cycles of 95˚C 20 s + 55˚C 10 s + 70˚C 9 s using KOD DNA polymerase.…”

Active nuclear import and cytoplasmic retention of activation-induced deaminase

“…This is highlighted by the cancer predisposition phenotype observed in transgenic mice overexpressing AID 7 , by the finding that ectopic SHM can occur in proto-oncogenes and tumor suppressor genes [8][9][10] and by the involvement of AID in oncogenic chromosomal translocations 11,12 . AID is normally induced in germinal center B cells 13 but in order to ensure that the genetic modifications it can cause are largely restricted to the Ig loci, there are multiple points of posttranscriptional regulation such as regulation of mRNA stability and translation [14][15][16] , subcellular localization 17,18 , protein stability 19 and modification by phosphorylation [20][21][22] .…”

AID and RAG1 do not contribute to lymphomagenesis in Eμ c-myc transgenic mice

“…We postulated that if AID were to play a role in lymphomagenesis, the frequency of mature B-cell lymphomas in AID À/À Em c-myc Tg mice would be significantly reduced because AID is only expressed in mature activated B cells (Muramatsu et al, 1999;Crouch et al, 2007). Therefore, we used flow cytometry to categorize the developmental status of lymphomas, as previously described (Egle et al, 2004).…”