Acta2BAC-GCaMP2 transgenic mice express the fluorescent calcium indicator GCaMP2 under control of the Acta2 locus promoter/enhancer regions within the BAC transgene. 

Acta2BAC-GCaMP2 transgenic mice from founder line 6 exhibit high sensor expression (GCaMP2 expression/EGFP fluorescence) in smooth muscle actin, including vessels. In total, transgene expression is consistent with endogenous Acta2.

In the absence of calcium binding, low/baseline EGFP fluorescence is observed. Following calcium binding (such as arteriolar vasodilation), bright EGFP fluorescence is observed.

Hemizygous and homozygous mice are viable and fertile with no reported gross physical or behavioral abnormalities. The donating investigator reports that homozygotes have brighter fluorescence than hemizygotes.

Calcium is a key molecular signal for cell functions including heart, smooth muscle, vessel, and airway contraction, lung secretion, autonomic neurotransmission and immunocyte function. Acta2BAC-GCaMP2 transgenic mice may be useful to examine calcium signaling in smooth muscle electrical and chemical signaling both in vivo and in vitro.

The genetically encoded calcium indicator GCaMP2 is a calcium-sensing molecule composed of a chicken smooth muscle M13 fragment of myosin light chain kinase, a circularly permutated EGFP (with several amino acid substitutions designed to increase brightness, dynamic range and thermal stability, as well as to prevent GFP dimerization), and a rat calmodulin sequence. In the absence of calcium binding, dim EGFP fluorescence is expected as there is a pore from the outside of its barrel into the chromophore. Upon calcium binding, this pore becomes occupied and fluorescence is increased.

This mouse model is available by way of a collaborative effort between Cornell/National Heart Lung Blood Resource for Optogenetic Mouse Signaling (<a href="http://chromus.vet.cornell.edu">CHROMus</a>) and The Jackson Laboratory.

Acta2BAC-GCaMP2 transgenic mice are a fluorescent calcium indicator strain that exhibits high calcium-sensor expression in smooth muscle actin, including vessels. Upon GCaMP2 binding to calcium, increased EGFP fluorescence is observed.

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