# Epiblast-derived CX3CR1+ progenitors generate cardiovascular cells during cardiogenesis

## TL;DR

This study shows that CX3CR1+ cells in mouse embryos are multipotent progenitors that contribute to heart development by forming cardiomyocytes, endothelial cells, and macrophages.

## Contribution

The study identifies CX3CR1+ cells as a novel multipotent progenitor population in the developing heart, capable of generating multiple cell types.

## Key findings

- CX3CR1+ cells originate from epiblast cells and contribute to parietal endoderm cells during early embryonic development.
- These cells differentiate into cardiomyocytes and endothelial cells via de novo differentiation and cell fusion.
- Mouse ESC-derived CX3CR1+ cells can generate cardiomyocytes, endothelial cells, and macrophages in vitro and in vivo.

## Abstract

CX3CR1+ cells generate tissue macrophages in the developing heart and play cardioprotective roles in response to ischemic injuries in the adult heart. However, the origin and fate of CX3CR1+ cells during cardiogenesis remain unclear. Here, we performed genetic lineage tracing of CX3CR1+ cells and their progeny (termed Cx3cr1 lineage cells) in the mouse and demonstrated that they emerge from a subset of epiblast cells at embryonic day E6.5 and contribute to the parietal endoderm cells at E7.0. At E8.0–9.5 of development, Cx3cr1 lineage cells produced cardiomyocytes and endothelial cells via both de novo differentiation and fusion with pre-existing cardiomyocytes or endothelial cells, respectively. Cx3cr1 lineage cells persisted in the adult heart, comprising ~13% of cardiomyocytes and ~31% of endothelial cells. Additionally, CX3CR1+ cells differentiated from mouse embryonic stem cells generated cardiomyocytes, endothelial cells, and macrophages in vitro, ex vivo, and in vivo. Single-cell RNA sequencing revealed that Cx3cr1+ cells represent an intermediate cell population transitioning from embryonic stem cells to mesoderm. Taken together, embryonic CX3CR1+ cells constitute a multipotent epiblast-derived progenitor population that contributes not only to the formation of macrophages, but also of cardiomyocytes and endothelial cells.

CX3CR1+ cells form tissue-resident macrophages in the heart that protect against cardiac injury. This study reveals CX3CR1+ cells as a multipotent progenitor population contributing also to cardiomyocytes and heart endothelial cells during early embryonic development.

CX3CR1+ cells emerge from a subset of epiblasts and subsequently contribute to the parietal endoderm cells.Epiblast-derived CX3CR1+ cells contribute to cardiomyocytes and endothelial cells.Cardiomyocytes and endothelial cells derived from prenatal CX3CR1+ cells persist in the adult heart.Mouse ESC-derived CX3CR1+ cells differentiate into cardiomyocytes and endothelial cells in the adult mouse heart.

CX3CR1+ cells emerge from a subset of epiblasts and subsequently contribute to the parietal endoderm cells.

Epiblast-derived CX3CR1+ cells contribute to cardiomyocytes and endothelial cells.

Cardiomyocytes and endothelial cells derived from prenatal CX3CR1+ cells persist in the adult heart.

Mouse ESC-derived CX3CR1+ cells differentiate into cardiomyocytes and endothelial cells in the adult mouse heart.

Lineage-tracing studies in mice reveal that CX3CR1+ progenitor cells, which give rise to cardiac macrophages, also differentiate into cardiomyocytes and endothelial cells during early heart development.