Abstract
The Gt(ROSA)26Sor ( ROSA26) and H11 loci are commonly used as safe harbors for the construction of targeted transgenic mice. However, it remains unclear whether these two loci have distinct effects on transgene expression. In this study, we insert three differently colored fluorescent protein expression cassettes (EGFP, tdTomato and mTagBFP2) driven by the CAG promoter into the ROSA26 and H11 loci. We generate five single-transgenic mouse models and a triple-transgenic mouse model expressing three distinct fluorescent proteins simultaneously. Our results reveal that the efficiency of transgene expression is greater at the ROSA26 locus with a reverse orientation relative to the transcription of the ROSA26 gene. In most tissues examined, the efficiency of transgene expression at the ROSA26 locus exceeds that at the H11 locus. Moreover, the expression profiles of identical transgenes display discrepancies across various tissues, and notably, substantial heterogeneity in transgene expression is discernible within cells of the same tissue. Our findings offer a valuable reference for the selection of safe harbors and strategies for the construction of transgenic mouse models.