Analysis of Qa-2 Antigen Expression by Preimplantation Mouse Embryos: Possible Relationship to the Preimplantation-Embryo-Development (Ped) Gene Product1

Abstract

The preimplantation-embryo-development (Ped) gene, a gene that controls the cleavage rate of preimplantation mouse embryos, maps to the Qa-2 subregion of the mouse major histocompatibility complex (MHC). A highly sensitive enzyme-linked immunosorbent assay (ELISA) procedure was used to detect Qa-2 antigens on mouse embryos. The use of a monoclonal antibody specific for Qa-2 antigens showed that Qa-2 antigens were present on oocytes, 2-cell, 8-cell, and blastocyst-stage embryos, with the greatest expression found on blastocysts. Expression of Qa-2 antigens by the embryos correlated completely with Ped gene phenotype. Those embryos expressing the fast Ped allele showed the presence of Qa-2 antigens (Qa-2a mice), whereas those embryos expressing the slow Ped allele showed the absence of Qa-2 antigens (Qa-2b mice). It is hypothesized that the Qa-2 antigen may be the Ped gene product.

HLA-G expression during preimplantation human embryo development.

“…Similarities at the DNA level (especially to murine genes Q7 or Q9) and its apparent lack of polymorphism suggest that HLA-G may be a structural homologue of the murine Qa-2 antigen (1). These molecules can be detected on murine oocytes and early-cleavage and blastocyst-stage embryos (29). Interestingly, the cleavage rate of mouse embryos has been shown to be linked to a gene designated "Ped" (preimplantation embryo development gene; ref.…”

Detection of H-2K mRNA in mouse 8-cell embryo by cDNA cloning.

“…In experiments using 8-cell mouse embryos, Krco and Goldberg (1977) detected H-2 antigens serologically on 8-cell mouse embryo cells, while Cozad and Warner (1982) demonstrated the presence of H-2 antigens for b-, k-and dhaplotypes using a highly sensitive complement-dependent cytotoxicity assay. Warner et al (1987b) further found Qa-2 antigens in preimplantation mouse embryos.…”

“…It has been suggested that the Q7 gene encodes Qa-2 antigen, and that its expression is modified by secreted, or cell-membrane associated compounds possibly by alternative splicing (Waneck et al, 1987). Though Qa-2 antigen has been detected in mouse embryos (Warner et al, 1987b), the nucleotide sequence of TE10 cDNA was significantly different from the Q7 cDNA sequence. Tla genes are another group of class I genes whose functions are unclear, but these were less closely related to TE 10 cDNA than were Qa genes (data not shown).…”

Embryonal carcinoma cells express Qa and Tla class I genes of the major histocompatibility complex.

“…Because the H-2, Qa, and Tla antigens are differentially expressed during early development (1,2), it has been hypothesized that they participate in embryonic cell-cell interactions. This hypothesis is supported by the observation that the gene encoding the Qa-2 antigen may determine the rate of cleavage of cells in the preimplantation embryo (3). Another hypothesis states that Qa and/or Tla antigens may serve as restriction elements recognized by the subset ofT lymphocytes expressing the T-cell receptor 'y-and S-chain complex (4)(5)(6).…”