Irx4 Marks a Multipotent, Ventricular-Specific Progenitor Cell

Abstract

Rationale While much progress has been made in the resolution of the cellular hierarchy underlying cardiogenesis, our understanding of chamber-specific myocardium differentiation remains incomplete. Objective To better understand ventricular myocardium differentiation, we targeted the ventricle-specific gene, Irx4, in mouse embryonic stem cells to generate a reporter cell line. Methods and Results Using an antibiotic-selection approach, we purified Irx4+ cells in vitro from differentiating embryoid bodies. The isolated Irx4+ cells proved to be highly proliferative and presented Cxcr4, Pdgfr-alpha, Flk1 and Flt1 on the cell surface. Single Irx4+ ventricular progenitor cells (VPC) exhibited cardiovascular potency, generating endothelial cells, smooth muscle cells and ventricular myocytes in vitro. The ventricular specificity of the Irx4+ population was further demonstrated in vivo as VPCs injected into the cardiac crescent subsequently produced Mlc2v+ myocytes that exclusively contributed to the nascent ventricle at E9.5. These findings support the existence of a newly identified ventricular myocardial progenitor. Conclusions This is the first report of a multipotent cardiac progenitor that contributes progeny specific to the ventricular myocardium.

Generation of multipotent induced cardiac progenitor cells from mouse fibroblasts and potency testing in ex vivo mouse embryos

“…The screening strategy and characterization criteria described in this protocol can be used to derive and benchmark novel CPC populations from embryos, pluripotent stem cells, as well as from the adult heart. The unique embryo injection model described here can be utilized to test the embryonic potency of other identified CPC populations, including CPCs derived from pluripotent stem cells 29 and adult heart derived CPCs. In addition to testing potency of cardiac cells, this protocol can be used to test the potency of cells for other mesodermal cell types, as well as for definitive ectoderm, definitive endoderm, and extra-embryonic cell types by injecting them into respective test sites.…”

Functional Transcription Factor Target Networks Illuminate Control of Epithelial Remodelling

“…Over-expression of IRX4 significantly increased invasion relative to controls in all conditions examined and IRX4 had high relative expression in a subset of basal-like breast cancers ( Figure 5 and Figure 6 ). IRX4 was a homeobox transcription factor involved in cardiogenesis, marking a ventricular-specific progenitor cell [ 142 ] and was also associated with prostate cancer risk [ 143 ]. SNX29 was poorly characterised, belonged to the sorting nexin protein family that function in endosomal sorting and signalling [ 144 ], and ectopic expression significantly reduced invasion in a SNAI1 -dependent manner ( Figure 6 ).…”

miR-128a Acts as a Regulator in Cardiac Development by Modulating Differentiation of Cardiac Progenitor Cell Populations

“…However, Sfrp5 expressed by progenitor cells mainly contributing to the left ventricle, sinus venosus, and parts of the atria [33], and the early first heart field progenitor cell marker Hcn4 [35]-also a predicted target of miR-128a-were significantly upregulated after 0.75 weeks (p < 0.01) ( Figure 3E). Interestingly, Irx4, which specifically marks ventricular progenitors [36], was significantly decreased at this timepoint (p < 0.05) ( Figure 3E). Most of the mentioned cardiac genes were not differentially expressed at later timepoints during differentiation ( Figure 3F, Figure S5B,C), indicating that miR-128a only acts during early cardiogenesis.…”