Neural cell adhesion molecule (NCAM-1) is required for ventricular conduction system development

Cardiac Purkinje cells (PCs) comprise the most distal portion of the ventricular conduction system (VCS) and are essential for synchronous activation of the ventricular myocardium. Contactin-2 (CNTN2), a member of the immunoglobulin superfamily cell adhesion molecules (IgSF-CAMs), was previously identified as a marker of the VCS. Through differential transcriptional profiling we discovered two additional highly enriched IgSF-CAMs in the VCS, NCAM-1 and ALCAM. Immunofluorescence staining showed dynamic expression patterns for each IgSF-CAM during embryonic and early post-natal stages, but ultimately all three proteins became highly enriched in mature PCs. Mice deficient in NCAM-1, but not CNTN2 or ALCAM, exhibited defects in Purkinje cell gene expression and VCS patterning, as well as cardiac conduction disease. Moreover, using ST8sia2 and ST8sia4 knockout mice, we show that inhibition of post-translational modification of NCAM-1 by polysialic acid (PSA) disrupts trafficking of sarcolemmal intercalated disc proteins to Purkinje cell junctional membranes and abnormal expansion of the extracellular space between apposing Purkinje cells. Taken together, our data provide novel insights into the complex developmental biology of the ventricular conduction system.