Acta2-Optoβ2AR-IRES-lacZ transgenic mice express the light-sensitive Optoβ2AR fusion protein and lacZ under control of the Acta2 locus promoter/enhancer regions within the BAC transgene. Acta2-Optoβ2AR-IRES-lacZ mice from founder line B7-5 exhibit robust expression levels of Optoβ2AR and lacZ in smooth muscle cells (e.g., blood vessels, lung airways, bladder and gut) - consistent with endogenous Acta2. Additional details described further below.
The Optoβ2AR fusion protein has the transmembrane and light-sensitive domains from bovine G protein-coupled protein rhodopsin with the intracellular domains from hamster β2-adrenergic receptor. When activated with light (~473 nm), Optoβ2AR generates the secondary messenger cyclic AMP (cAMP).
For Acta2-Optoβ2AR-IRES-lacZ transgenic mice, light activation of the Optoβ2AR molecule in smooth muscle results in release of cAMP, causing a cascade reaction and muscle relaxation.
The donating investigator reports that expression patterns appear to mimic the endogenous Acta2 expression. Specifically, lacZ staining was observed in blood vessels (heart, lung, diaphragm and brain), small intestine and bladder. Optoβ2AR activation with light was observed in blood vessels (cremaster and femoral vessels). They have not tested expression in other smooth muscle-containing tissues to date (February 2019). Before exposure to the specific wavelength of activating light, lacZ expression is observable, and the Optoβ2AR imparts no cAMP release and no muscle relaxation. Upon exposure to ~473 nm light, Optoβ2AR activation releases cAMP and results in muscle relaxation. Subsequent removal of the activating light returns muscle to the baseline state (allowing contraction).
Mice hemizygous for the Acta2-Optoβ2AR-IRES-lacZ transgene are viable and fertile with normal breeding, and no reported gross phenotypic abnormalities. To date (February 2019), it has not been attempted to make this strain homozygous. As a precaution, the donating investigator does not recommend making this strain homozygous, due to some incidence of lethality in other mouse lines created using the same BAC (e.g., Stock Nos. 025406/028348).
This mouse model is available by way of a collaborative effort between Cornell/National Heart Lung Blood Resource for Optogenetic Mouse Signaling (CHROMus) and The Jackson Laboratory.
