Genetic targeting of Purkinje fibres by Sema3a-CreERT2

Abstract

The maintenance of the heart rhythm and the conduction of excitatory signals require changing excitatory signals via electrical activity and coordination by communication between working and conductive cardiomyocytes. Understanding how the ventricular conduction system is established provides novel insights into the pathophysiological progress of cardiac arrhythmias. However, the major hurdle in this field is the lack of a specific genetic tool that targets the Purkinje fibres of the ventricular conduction system and no other types of cardiomyocytes or coronary vessels. Here, we generated a Sema3a-CreERT2 knock-in mouse line to test its specificity for genetically labelled Purkinje fibres. We found that Sema3a was expressed in the subendocardial layer of the trabecular myocardium in the embryonic heart and was restricted to the Purkinje fibres in the adult heart. A fate mapping study based on the Sema3a-CreERT2 line revealed that the Sema3a+ cardiomyocytes were restricted to the fate of Purkinje fibres in the perinatal but not the embryonic stage. Collectively, our study provides a new genetic tool, i.e., Sema3a-CreERT2, for studying the molecular mechanisms that regulate the function of Purkinje fibres.

Nkx2-5 defines distinct scaffold and recruitment phases during formation of the murine cardiac Purkinje fiber network

“…In contrast, after tamoxifen injection at P1, Cx40 -derived cell numbers are reduced and restricted to the VCS. Consistent with previous reports, this shows the progressive fate restriction of Cx40 -positive trabecular cells to the VCS lineage 24 .…”

Nkx2-5 defines distinct scaffold and recruitment phases during formation of the cardiac Purkinje fiber network

“…Consistent with previous reports, this shows the progressive fate restriction of Cx40-positive trabecular cells to the VCS lineage 24 .…”

Defects in Trabecular Development Contribute to Left Ventricular Noncompaction

“…Lineage tracing of Cx40+ trabecular cells indicates that the coalescence of trabeculae into the ventricular wall correlates with the progressive restriction of Cx40 expression to the conduction system. This pattern of expression is similar to that of Sema3a, another PFs marker [26]. Furthermore, this lineage restriction is accompanied by a decrease in the number of Cx40+ trabecular progenitors, and a progressive integration of Cx40-derived cells into the working myocardium.…”

“…Segregation into a conductive fate is associated with a reduced proliferative capacity compared to contractile cardiomyocytes that exhibit a high proliferative rate until perinatal stages [37]. Furthermore, the progressive segregation of trabecular cardiomyocytes into cells with a contractile myocardial fate is accompanied by the gradual loss of expression of trabecular markers including Etv1, Irx3, Cx40 and Sema3a, the expression of which becomes restricted to the VCS at postnatal stages [6,23,25,26,38] (Fig. 1B).…”

“…Indeed, a balance between proliferation and differentiation is critical to both generate a sufficient number of cells and initiate lineage specification [22]. The trabecular zone is characterized by the expression of the genes Irx3, Cx40, Nppa, Etv1, Bmp10, Slit2 and Sema3a whereas the compact zone is characterized by the expression of Tbx20, Hey2, Loxl2 and N-Myc [6,[22][23][24][25][26][27][28] (Fig. 1A).…”