Quantitative analysis of integrated Ed alpha gene expression in C57BL/6 transgenic mice

We performed quantitative analysis of Ed alpha gene expression in the transgenic mice, created by microinjecting cloned Ed alpha gene fragments into C57BL/6 fertilized eggs. DNA dot-blot analysis revealed that Ed alpha gene-introduced transgenic mice (B6Ed alpha transgenic mice) contain 20 copies per cell of the Ed alpha gene in their genome. RNA dot-blot analysis revealed that the amount of Ed alpha mRNAs in B6Ed alpha transgenic spleen cells is 20-40-fold higher than those in normal BALB/c or (BALB x C57BL/6)F1 (CBF1) spleen cells. However, the amount of Ed alpha molecules expressed on B6Ed alpha transgenic spleen cells was similar to that expressed on normal BALB/c of CBF1 spleen cells on a gene-dose basis. The amount of endogenous Ed alpha mRNA in the B6Ed alpha transgenic spleen cells was almost equal to that of normal B6 spleen cells. Since the cell surface I-E molecule is formed by non-covalent association of E alpha and E beta chain, these results suggest that, in spite of the high expression of integrated Ed alpha gene in the cytoplasm of B6Ed alpha transgenic mice, the amount of Ed alpha gene expression on the cell surface is limited by the amount of endogenous Eb beta gene products.