FIG. 3.

hCD79b mRNA levels in splenic lymphocytes of transgenic mice. A. Transgenes are depicted. The map of the CD79b gene and its 5′-flanking region indicates the positions of B-cell-specific HS (black arrows) and the two HS specific to the pituitary gland (HSI and HSII; white arrows) for reference. A CpG hypomethylated region of DNA specific to B cells is shown (stippled circle). The four CD79b transgenes are indicated on the map along with their respective sizes. The name of each of these transgenes corresponds to the length of the 5′-flanking region in each case. B. Quantitation of human versus mouse CD79b mRNAs. hCD79b mRNA and endogenous mCD79b mRNA were reverse transcribed (RT) coamplified from B cells purified from the spleens of the indicated transgenic mice. The coamplification was accomplished using a set of conserved sequence primers (mhIgβ forward and reverse; Table 2; white horizontal arrows). The PCR product spans exons 5 and 6, permitting size spliced RNA products. The cDNAs corresponding to human and mouse mRNAs were differentiated by restriction enzyme cleavage. Digestion of the 5′ ³²P end-labeled cDNA products with SfcI (S) will exclusively generate the hCD79b cDNA product (95 bp), whereas digestion with HinfI (H) exclusively generates the mCD79b cDNA product (63 bp). A diagram of the predicted fragment migration on an analytic gel is represented. C to G. hCD79b mRNA expression in B cells of each CD79b transgenic mouse line. For each transgene, five independent lines with unique transgene insertion sites were analyzed. Signals corresponding to the human and mouse CD79b mRNAs were determined according to the scheme depicted in panel B. The SfcI (S) and HinfI (H) digestion products were quantified, and the human/mouse mRNA ratio was divided by the transgene copy number (indicated below each pair of lanes). The results of hCD79b mRNA expression per transgene copy were expressed as a percentage of a single endogenous mCD79b gene (also shown below each pair of lanes). H. Summary of CD79b mRNA expression in B cells of the six transgenic mouse lines. The hCD79b expression percentages derived from analysis of each of the transgenic lines (C to G) are displayed on the semilog plot. The value from each line, shown as a diamond, reflects the average of two or more independent assays. The data from the hGH/P1 lines have been previously reported (5) and are included to facilitate comparisons.