Abstract
The coxsackievirus-adenovirus receptor (CAR) is a cell contact protein on various cell types with unknown physiological function. It belongs to a subfamily of the immunoglobulin-superfamily of which some members are junctional adhesion molecules on epithelial and/or endothelial cells. CAR is dominantly expressed in the hearts and brains of mice until the newborne phase after which it becomes mainly restricted to various epithelial cells. To understand more about the physiological function of CAR, we have generated CAR-deficient mice by gene targeting. We found that these mice die between E11.5 and E13.5 of embryonal development. Ultrastructural analysis of cardiomyocytes revealed that the density of myofibrils was reduced and that their orientation and bundling was disorganized. In addition, mitochondria were enlarged and glycogen storage strongly enriched. In line with these defects, we observed pericardial edema formation as a clear sign of insufficient heart function. Developmental abnormalities likely to be secondary effects of gene ablation were the persistent singular cardial atrio-ventricular canal and dilatations of larger blood vessels such as the cardinal veins. The secondary nature of these defects was supported by the fact that CAR was not expressed on vascular cells or on cells of the vascular wall. No obvious signs for alterations of the histological organization of the placenta were observed. We conclude that CAR is required for embryonal heart development, most likely due to its function during the organization of myofibrils in cardiomyocytes.
Highlights
The coxsackievirus-adenovirus-receptor (CAR) was originally found as a cell surface protein enabling both viruses to interact with cells (Bergelson et al, 1997; Tomko et al, 1997)
Ultrastructural analysis of cardiomyocytes revealed that the density of myofibrils was reduced and that their orientation and bundling was disorganized
We conclude that coxsackievirus-adenovirus receptor (CAR) is required for embryonal heart development, most likely due to its function during the organization of myofibrils in cardiomyocytes
Summary
The coxsackievirus-adenovirus-receptor (CAR) was originally found as a cell surface protein enabling both viruses to interact with cells (Bergelson et al, 1997; Tomko et al, 1997). Some of the members of this subfamily are found at endothelial and/or epithelial tight junctions, such as the junctional adhesion molecules (JAM-A, -B and -C) (AurrandLions et al, 2000; Ebnet et al, 2004; Martin-Padura et al, 1998) and endothelial-selective cell adhesion molecule (ESAM) (Hirata et al, 2001; Nasdala et al, 2002). The latter is selectively expressed on endothelium and platelets, and is structurally most closely related to CAR
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