Ciona as a Simple Chordate Model for Heart Development and Regeneration.

Heather Evans Anderson,Lionel Christiaen

doi:10.3390/jcdd3030025

Abstract

Cardiac cell specification and the genetic determinants that govern this process are highly conserved among Chordates. Recent studies have established the importance of evolutionarily-conserved mechanisms in the study of congenital heart defects and disease, as well as cardiac regeneration. As a basal Chordate, the Ciona model system presents a simple scaffold that recapitulates the basic blueprint of cardiac development in Chordates. Here we will focus on the development and cellular structure of the heart of the ascidian Ciona as compared to other Chordates, principally vertebrates. Comparison of the Ciona model system to heart development in other Chordates presents great potential for dissecting the genetic mechanisms that underlie congenital heart defects and disease at the cellular level and might provide additional insight into potential pathways for therapeutic cardiac regeneration.

Highlights

The animal species comprising the phylum Chordata display very diverse cardiac morphologies and physiology
These studies led to the proposal that the pattern observed in Ciona represents a simplified version of an ancestral/ancient cardiopharyngeal ontogenetic motif, whereby multipotent progenitors progress through transient regulatory states marked successively by Mesp1, Nkx2-5, Tbx1, and Islet1 homologs and produce distinct first and second heart field progenitors, and pharyngeal muscles precursors and associated stem cells (Figure 5); [36,38]
We propose that Tbx1/10, Ebf and Mrf homologs are part of an ancient transcriptional network for pharyngeal muscle specification [85], with a role in opposing cardiac development in the cardiopharyngeal lineage

Summary

Introduction

The animal species comprising the phylum Chordata display very diverse cardiac morphologies and physiology. Cardiac features are highly-adaptive such that diffusely contractile vessels in cephalochordates, simple peristaltic compartments in Tunicates, and multi-chambered pumps with separate high and low pressure circulation in amniotes reflect the evolution and divergence of Chordate species Across this diversity lies a deeply conserved network of genetic determinants for cardiac cell specification and patterning. Examining cardiac fate-specification programs and conserved regulatory states of cardiac progenitor cells during Ciona heart development, as compared to vertebrates, presents an opportunity to examine the basic building blocks of the Chordate heart program in a simple model system. A comparison of the Ciona model system to heart development in other Chordates presents great potential for dissecting the genetic mechanisms that underlie congenital heart defects and disease at the cellular level, as well as provides insight into potential pathways for therapeutic cardiac regeneration

Divergent Cardiac Anatomy and Histology

Development of the Ciona Heart and Parallels with the Vertebrates

Ciona as an Experimental Model for Cardiac Regeneration

Concluding Remarks