Smooth muscle protein 22 alpha-Cre is expressed in myeloid cells in mice.

Background: Experiments using Cre recombinase to study smooth muscle specific functions rely on strict specificity of Cre transgene expression. Therefore, accurate determination of Cre activity is critical to the interpretation of experiments using smooth muscle specific Cre.

Methods And Results: Two lines of smooth muscle protein 22 α-Cre (SM22α-Cre) mice were bred to floxed mice in order to define Cre transgene expression.