A New Autosomal Myh11-CreER(T2) Smooth Muscle Cell Lineage Tracing and Gene Knockout Mouse Model-Brief Report

Background:The Myh11 promoter is extensively used as a smooth muscle cell (SMC) Cre-driver and is regarded as the most restrictive and specific promoter available to study SMCs. Unfortunately, in the existing Myh11-CreER(T2) mouse, the transgene was inserted on the Y chromosome precluding the study of female mice. Given the importance of including sex as a biological variable and that numerous SMC-based diseases have a sex-dependent bias, the field has been tremendously limited by the lack of a model to study both sexes. Here, we describe a new autosomal Myh11-CreER(T2) mouse (referred to as Myh11-CreER(T2)-RAD), which allows for SMC-specific lineage tracing and gene knockout studies in vivo using both male and female mice. Methods:A Myh11-CreER(T2)-RAD transgenic C57BL/6 mouse line was generated using bacterial artificial chromosome clone RP23-151J22 modified to contain a Cre-ERT2 after the Myh11 start codon. Myh11-CreER(T2)-RAD mice were crossed with 2 different fluorescent reporter mice and tested for SMC-specific labeling by flow cytometric and immunofluorescence analyses. Results:Myh11-CreER(T2)-RAD transgene insertion was determined to be on mouse chromosome 2. Myh11-CreER(T2)-RAD fluorescent reporter mice showed Cre-dependent, tamoxifen-inducible labeling of SMCs equivalent to the widely used Myh11-CreER(T2) mice. Labeling was equivalent in both male and female Cre(+) mice and was limited to vascular and visceral SMCs and pericytes in various tissues as assessed by immunofluorescence. Conclusions:We generated and validated the function of an autosomal Myh11-CreER(T2)-RAD mouse that can be used to assess sex as a biological variable with respect to the normal and pathophysiological functions of SMCs.

Automated summary

This study introduces a new Myh11-CreER(T2)-RAD mouse model that can be used for lineage tracing and gene knockout studies of smooth muscle cells (SMCs) in both male and female mice. The innovation of this model is that the Myh11 transgene is inserted into mouse chromosome 2, allowing for study in female mice. Flow cytometric and immunofluorescence analyses of mouse samples confirmed that this model can label vascular and visceral SMCs and pericytes.