Inducible Cardiac-Specific Cavβ2a Overexpression

FVB mouse strain was used in our study. Cardiac myocyte specific [α-myosin heavy chain (MHC) promoter] with inducible tetracycline-activator (tTA) expression of the β2a-subunit of L-type Ca²⁺ channel (Cavβ2a) was used. This β2a-Tg with relatively low expression level was documented (Supplemental Fig. S3; all Supplemental material is available at https://www.doi.org/10.6084/m9.figshare.22068815) (21 (link)). The overexpression of β2a-subunit increases the open probability and membrane trafficking of the pore-forming Cav1.2α1c-subunit, which further increased Ca²⁺ influx in cardiomyocytes as previously reported (21 (link), 22 (link)).
The β2a-Tg mice were established with the inducible (tet-off), bitransgenic system (22 (link)) (Supplemental Fig. S3). Mice with the tetracycline transactivator (tTA) driver gene and the Cavβ2a gene (double transgenic, DTG) without the doxycycline-containing chow were used as our β2a-Tg experimental group. Doxycycline is a derivative of tetracycline and hence represses β2a transgene expression. The Cavβ2a transgene was not expressed until adulthood to avoid developmental complications (22 (link)). For each litter, β2a-Tg mice were separated into different treatment cohorts, and their WT mice littermates were separated into corresponding treatments as well. Sex-matched animals (β2a-Tg and WT mice) were given different treatments at the age of 4 mo when the Cavβ2a gene had been fully expressed.