CREATION OF MICE EXPRESSING HUMAN-ANTIBODY LIGHT-CHAINS BY INTRODUCTION OF A YEAST ARTIFICIAL CHROMOSOME CONTAINING THE CORE REGION OF THE HUMAN IMMUNOGLOBULIN-KAPPA LOCUS

We have previously described a strategy for integrating selectable mar ker genes into yeast artificial chromosomes (YACs) to facilitate their transfer into embryonic stem (ES) cells. Here we apply this technolog y to create mice carrying the core region of the human immunoglobulin (lg) kappa light chain locus. A YAC was isolated which contains a 300 kb insert spanning three Vkappa segments, the Jkappa cluster, the Ckap pa region and extending downstream of the Kde element. After modificat ion of this YAC to integrate the selectable neo marker gene, the YAC w as introduced into ES cells by protoplast fusion. Several ES cell clon es were obtained which appeared to harbor one complete copy of the YAC while retaining little or no other yeast DNA. The ES cells were injec ted into blastocysts and the chimaeric mice were shown to rearrange th e introduced human light chain genes with the resultant production of antibodies containing human kappa light chains in the serum.