Somatic Mutations During an Immune Response in Xenopus Tadpoles

Abstract

The tadpole B-cell repertoire is less diverse than that of the adult frog; their antibodies are of lower affinity and are less heterogenous. In order to determine whether this difference is due to a lack of or a reduced rate of somatic hypermutation, we analyzed and compared cDNA sequences utilizing V_H1 elements with germline counterparts in isogenic LG7 tadpoles during an immune response. Indeed, tadpole V_H1 sequences contained somatic mutations. There were zeo to 5 mutations per sequence, all single base-point mutations, with the high ratio of GC to AT base-pair alterations similar to that observed in adult frogs.