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Activation-induced cytidine deaminase turns on somatic hypermutation in hybridomas


The production of high-affinity protective antibodies requires somatic hypermutation (SHM) of the antibody variable (V)-region genes. SHM is characterized by a high frequency of point mutations that occur only during the centroblast stage of B-cell differentiation. Activation-induced cytidine deaminase (AID), which is expressed specifically in germinal-centre centroblasts1, is required for this process, but its exact role is unknown2. Here we show that AID is required for SHM in the centroblast-like Ramos cells, and that expression of AID is sufficient to induce SHM in hybridoma cells, which represent a later stage of B-cell differentiation that does not normally undergo SHM. In one hybridoma, mutations were exclusively in G·C base pairs that were mostly within RGYW or WRCY motifs, suggesting that AID has primary responsibility for mutations at these nucleotides. The activation of SHM in hybridomas indicates that AID does not require other centroblast-specific cofactors to induce SHM, suggesting either that it functions alone or that the factors it requires are expressed at other stages of B-cell differentiation.

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Figure 1: hAID expression induces SHM in non-mutating Ramos cells.
Figure 2: AID induces SHM in hybridomas.
Figure 3: Mutations observed in hybridoma clones.


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We thank B. Diamond, J. Warner, M. Goodman and R. Laskov for critical review of the manuscript, and A. Bothwell for providing the P1-5 hybridoma. This work was supported by grants from the National Institutes of Health to P.D.B., to C.J.W. and to M.D.S., who is also supported by the Harry Eagle chair provided by the National Women's Division of the Albert Einstein College of Medicine. A.M. is a recipient of Cancer Research Institute and Harry Eagle fellowships.

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Correspondence to Matthew D. Scharff.

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Martin, A., Bardwell, P., Woo, C. et al. Activation-induced cytidine deaminase turns on somatic hypermutation in hybridomas. Nature 415, 802–806 (2002).

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