Characterization of immunoglobulin heavy chain knockout rats

The rat is a species frequently used in immunological studies but, until now, there were no models with introduced gene-specific mutations. In a recent study, we described for the first time the generation of novel rat lines with targeted mutations using zinc-finger nucleases. In this study, we compare immune development in two Ig heavy-chain KO lines; one with truncated C mu and a new line with removed JH segments. Rats homozygous for IgM mutation generate truncated C mu mRNA with a de novo stop codon and no C gamma mRNA. JH-deletion rats showed undetectable mRNA for all H-chain transcripts. No serum IgM, IgG, IgA and IgE were detected in these rat lines. In both lines, lymphoid B-cell numbers were reduced >95% versus WT animals. In rats homozygous for IgM mutation, no Ab-mediated hyperacute allograft rejection was encountered. Similarities in B-cell differentiation seen in Ig KO rats and ES cell-derived Ig KO mice are discussed. These Ig and B-cell-deficient rats obtained using zinc-finger nucleases-technology should be useful as biomedical research models and a powerful platform for transgenic animals expressing a human Ab repertoire.