SEQUENCE AND TRANSCRIPTION OF QA-2-ENCODING GENES IN MOUSE LYMPHOCYTES AND BLASTOCYSTS

The protein product of the mouse preimplantation embryo development (F ed) gene, which controls the rate of preimplantation embryonic cleavag e division and subsequent embryo survival, is the Qa-2 antigen. This m ajor histocompatibility complex (MHC) class Ib protein is encoded by f our genes, Q6, Q7, Q8, and Q9. The present study was undertaken to beg in to elucidate which of the four Qa-2-encoding genes are responsible for the Fed gene phenotype in the C57BL/6 mouse (H2b). First, restrict ion maps of the four genes, using 25 restriction enzymes, were created . The RE maps confirmed that Q6 is similar to Q8 and Q7 is similar to Q9, but that the Q6/Q8 gene pair differs from the Q7/Q9 gene pair. The genomic DNA sequences of Q6 and Q8 were determined, as well as the DN A sequences of exons 4-8 of Q9, and the 5' regulatory regions of Q6, Q 8, and Q9. This DNA sequence information, combined with the published DNA sequence information for the entire Q7 gene and exons 1-3 of Q9, a llowed us to design primers for reverse transcription-polymerase chain reaction that could distinguish which of the four genes were transcri bed in mouse lymphocytes and embryos. It was found that all four genes are transcribed in lymphocytes, but only Q7 and Q9 are transcribed in mouse embryos. Thus, both Q7 and Q9 are candidates for the genes resp onsible for the Ped gene phenotype.