Deletion of the Wilms' Tumor Suppressor Gene in the Cardiac Troponin-T Lineage Reveals Novel Functions of WT1 in Heart Development.

Sandra Díaz Del Moral,Amelia Aránega,José Manuel Villaescusa,Ramón Muñoz-Chápuli,Diego Franco,Rita Carmona,Manuel Jiménez-Navarro,Silvia Barrena,Francisco Hernández-Torres,Juan José Gómez Doblas

doi:10.3389/fcell.2021.683861

Abstract

Expression of Wilms’ tumor suppressor transcription factor (WT1) in the embryonic epicardium is essential for cardiac development, but its myocardial expression is little known. We have found that WT1 is expressed at low levels in 20–25% of the embryonic cardiomyocytes. Conditional ablation of WT1 using a cardiac troponin T driver (Tnnt2Cre) caused abnormal sinus venosus and atrium development, lack of pectinate muscles, thin ventricular myocardium and, in some cases, interventricular septum and cardiac wall defects, ventricular diverticula and aneurisms. Coronary development was normal and there was not embryonic lethality, although survival of adult mutant mice was reduced probably due to perinatal mortality. Adult mutant mice showed electrocardiographic anomalies, including increased RR and QRS intervals, and decreased PR intervals. RNASeq analysis identified differential expression of 137 genes in the E13.5 mutant heart as compared to controls. GO functional enrichment analysis suggested that both calcium ion regulation and modulation of potassium channels are deeply altered in the mutant myocardium. In summary, together with its essential function in the embryonic epicardium, myocardial WT1 expression is also required for normal cardiac development.

Highlights

The Wilms tumor suppressor gene (Wt1) encodes a C2H2-type zinc-finger transcription factor that appears in mammals under different isoforms, participating in transcriptional regulation, RNA metabolism and protein-protein interactions
The aim of this report is to study in depth the myocardial expression of WT1 and to investigate if conditional deletion of WT1 in embryonic cardiomyocytes causes alterations in cardiac development, anomalies that could have been hitherto masked in previous descriptions of systemic or epicardial-specific loss of function
WT1 Is Expressed in a Fraction of Cardiomyocytes During Development

Summary

Introduction

The Wilms tumor suppressor gene (Wt1) encodes a C2H2-type zinc-finger transcription factor that appears in mammals under different isoforms, participating in transcriptional regulation, RNA metabolism and protein-protein interactions. Systemic loss of function of WT1 in mice causes embryonic lethality at midgestation, a lethality attributed to defects in cardiac development (Martínez-Estrada et al, 2010; Cano et al, 2016). WT1 is highly expressed in the embryonic epicardium where it regulates a process of epicardial-mesenchymal transformation and the development of the epicardial-derived cells that contribute with fibroblasts and smooth muscle to the cardiac connective and vascular tissues (Martínez-Estrada et al, 2010; Von Gise et al, 2011). The phenotype of WT1 loss of function in mice involves thinning of the myocardial walls associated to a defective coronary development, the most probable cause of the embryonic death (Lavine et al, 2005; Vega-Hernández et al, 2011)

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