Because of the role major histocompatibility complex (MHC) class I b molecules may play during mouse embryonic development,
we thought it would be interesting to search for additional MHC class I b molecules that might be expressed in preimplantation
embryos, and in particular in the trophoblastic lineage. We therefore screened a mouse preimplantation blastocyst cDNA library
for
MHC class I sequences. This search led to the identification and characterization of a new
MHC class I b gene, blastocyst
MHC. Sequences identical to the exons and 3′ untranslated region of this gene have been found in many laboratory mouse strains,
as well as in the related mouse species
Mus spreciligus. The presence of this gene in mouse strains of different
MHC class I haplotypes argues that blastocyst
MHC is a unique, newly-described gene rather than a new allele of a previously described mouse
MHC class I gene. Blastocyst
MHC has the structure of an
MHC class I b gene, with the six exons characteristic of
T-region genes. It is linked to
H2-D. The amino acid sequence encoded by this gene maintains all the features of a functional antigen-presentation domain. The
blastocyst
MHC gene, like the human class I b gene
HLA-G, is expressed at the blastocyst stage and in the placenta, and may be the mouse analog for
HLA-G.
Received: 31 May 1996 / Revised: 19 August 1996
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