Unusual expression pattern of the MHC class I Q5k gene in the AKR mouse: possible role in embryo development.

Analysis of the tissue-specific expression of the Q5k gene in the AKR mouse reveals an unusual expression pattern. The Q5k mRNA is present in embryos from day 12, but expression is switched off in most tissues except thymus and testis shortly after birth. Late in pregnancy the gene is again transcribed in females. Analysis at the epitope level, with a Qa-2 specific monoclonal antibody revealed that in most cases the Q5k product is confined to the cytoplasm. These results suggest that Q5k has a most unusual tissue distribution and timing of expression among all the H-2 class I and Q genes so far described.