Neural cell adhesion molecule is required for ventricular conduction system development.

Camila Delgado,Feng-Xia Liang,Glenn I Fishman,Andrew J Furley,Fang-Yu Liu,Lei Bu,Joseph Sall,Jie Zhang

doi:10.1242/dev.199431

Abstract

ABSTRACTThe most distal portion of the ventricular conduction system (VCS) contains cardiac Purkinje cells (PCs), which are essential for synchronous activation of the ventricular myocardium. Contactin-2 (CNTN2), a member of the immunoglobulin superfamily of 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 postnatal 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 PC 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 leads to disrupted trafficking of sarcolemmal intercalated disc proteins to junctional membranes and abnormal expansion of the extracellular space between apposing PCs. Taken together, our data provide insights into the complex developmental biology of the ventricular conduction system.

Highlights

The cardiac conduction system (CCS) is responsible for tightly regulating the normal rhythmicity of the heart
Given the co-expression of multiple IgSF-CAMs in Purkinje cells (PCs), we focused our attention on activated leukocyte cell adhesion molecule (Alcam) and neural cell adhesion molecule 1 (Ncam-1)
Using a loss-of-function strategy for each of these three IgSF-CAMs, we demonstrate that neural cell adhesion molecule 1 (NCAM-1), but not contactin 2 (CNTN2) or activated leukocyte cell adhesion molecule (ALCAM), is essential for normal development of the ventricular conduction system (VCS)

Summary

Introduction

The cardiac conduction system (CCS) is responsible for tightly regulating the normal rhythmicity of the heart. Leveraging the CCS-lacZ reporter mouse (Logan et al, 1993; Rentschler et al, 2001) and differential transcriptional profiling, we previously reported the highly enriched expression of the cell adhesion protein contactin 2 (CNTN2) in the VCS (Pallante et al, 2010). This member of the immunoglobulin superfamily of cell adhesion molecules (IgSF-CAMs) was weakly expressed in the ventricular myocardium in late-stage fetal hearts, but soon after birth its expression was markedly upregulated and highly restricted to PCs within the VCS (Maass et al, 2015). Using Cntn2-EGFP BAC transgenic reporter mice, which faithfully recapitulate expression of endogenous Cntn (Heintz, 2004; Pallante et al, 2010), our laboratory subsequently identified a number of additional highly enriched transcripts in PCs, including ETS variant transcription factor 1 (ETV1), a key transcriptional regular of the ‘fast conduction’ transcriptome in the atria and VCS (Shekhar et al, 2016), as well as Purkinje cell protein 4 (PCP4), a small IQ motif-containing protein implicated in intracellular calcium homeostasis and PC excitability (Kim et al, 2014)

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Conclusion