Generation of a novel constitutive smooth muscle cell-specific -driven Cre mouse model.

Dysfunction in either embryonic or postnatal vascular smooth muscle cells (SMCs) significantly contributes to the progression of various cardiovascular diseases. Therefore, elucidating the molecular mechanisms governing VSMC development and homeostasis is crucial. is the most reliable lineage gene for SMCs and has been utilized to develop tamoxifen-inducible Cre driver lines for achieving SMC-specific gene manipulation by crossing with mice carrying the lox -flanked gene, particularly in adult mice. For studies involving SMCs during embryogenesis, the commonly used constitutive Cre driver is controlled by the ( ) promoter. However, this Cre driver exhibits activity in multiple non-SMC populations, including cardiomyocytes and skeletal muscle precursors, introducing confounding effects. Additionally, most existing SMC-specific Cre drivers are generated using a transgenic approach, raising concerns about random site integration and variable gene copy numbers. To address these limitations, we report a novel Cre mouse model generated by knock-in (KI) of a nuclear-localized Cre recombinase into the gene locus using homologous recombination. We confirmed that the Cre activity precisely recapitulates endogenous expression by crossing with mTmG or tdTomato reporter mice. Moreover, -driven Cre can efficiently delete the floxed allele of the transcription factor specifically in SMCs. The SMC-specific knockout mice did not exhibit an overt phenotype, thereby circumventing the embryonic lethal phenotype mediated by -driven Cre, as we previously reported. These findings establish this novel Cre driver line as a robust tool for tracing the -positive SMC lineage and manipulating gene function specifically in SMCs during embryonic development in mice.