Figure 1.

Insertion of the PGK-neo^r gene in the IgH locus disrupts class switching upstream of the insertion. Summary of the effects on CSR in gene-targeting experiments within the IgH locus using the PGK-neo^r gene as a selectable marker. Iγ2b and IgE C_H1–4 summarize experiments presented here, and HS1,2 and HS3a summarize previously published studies (24, 25). The effect on CSR is noted as inhibition (downward-pointing arrow), partial inhibition (+/−), or CSR levels comparable to wt controls (+). Transcripts and transcriptional orientation are represented by horizontal arrows. ND, not determined. I, I exon; S, switch region; C, constant region genes for corresponding isotype.