Generation of transchromosomic mice harboring HLA-A/B/C and human B2M via mouse artificial chromosome and triple BAC integration.

Humanized transgenic mice carrying human genes are useful for research on gene function and disease. Bacterial artificial chromosomes (BACs) that carry human genomic sequences with regulatory elements enable the expression of transgenes at physiological levels in vivo. To study complex biological phenomena involving multiple genes, techniques for co-introducing transgenes into mice have been developed; however, the introduction of multiple BACs remains laborious. The simultaneous integration of multiple gene loading vectors (SIM) system was developed to incorporate three or more gene-loading vectors (GLVs) using a mouse artificial chromosome (MAC) vector. This system allows for simultaneous site-specific incorporation of three GLVs into a single MAC with only one screening. However, the capacity for large constructs, such as BACs, has yet to be evaluated. This study is the first to demonstrate the development of multi-BAC transchromosomic (Tc) mice targeting the human leukocyte antigen (HLA) class I gene cluster (HLA-A, HLA-B, HLA-C) and beta-2-microglobulin (B2M) using the SIM system. By constructing a MAC using three BACs containing these genomic regions, we successfully generated HLA class I Tc mice. The technology to generate multi-BAC Tc mice will accelerate the analysis of complex life mechanisms involving multiple factors.