Interleaved intersectional strategy enables genetic lineage tracing with enhanced specificity

Dual recombinases have been increasingly employed for enhanced precision in genetic targeting. Recent studies utilizing an intersectional genetic approach have revealed that fibroblasts derived from the endocardium (EndoFb) play a pivotal role in cardiac fibrosis. However, this strategy faces limitations primarily due to the potential ectopic genetic labeling by the constitutive Dre recombinase, especially in undesired cells within the adult heart. To overcome this challenge, we have developed an advanced interleaved intersectional reporter (IIR) strategy. This IIR strategy leverages an inducible Cre recombinase to prevent inadvertent recombination by Dre upon Tamoxifen injection, thereby allowing for more specific labeling of EndoFb for fibrosis research. Moreover, our IIR system incorporates Diphtheria Toxin Receptor (DTR), facilitating the genetic ablation of targeted cells. We have successfully applied this strategy to specifically target fibroblasts derived from the epicardium (EpiFb) and tissue-resident macrophages. Consequently, this method enhances the precision of genetic lineage tracing while still employing the constitutive Dre recombinase in tandem with inducible Cre. ### Competing Interest Statement The authors have declared no competing interest.