Heart formation in vertebrates

Lead Research Organisation: The Francis Crick Institute

Abstract

Formation of the heart is a complex process that begins very early in the vertebrate embryo, remodelling a simple pulsatile tube into a multi-chambered organ capable of supporting embryo growth.
This transformation requires exquisite coordination of cell differentiation, growth and dramatic changes in organ shape. Abnormalities affecting any step have profound consequences on the foetal heart, with the result that heart defects are the most common birth defect.
By studying the roles of individual genes and cell populations in normal heart development, our work aims to provide a better understanding of the origins of cardiac malformations and how this complex organ is formed in the developing embryo. This may also contribute to our understanding of cardiac disease since accumulating evidence suggests that the same genes regulating normal heart development are important in both the normal and pathological adult heart phenotype.

Technical Summary

This work was supported by the Francis Crick Institute which receives its core funding from the UK Medical Research Council (FC001000), the Wellcome Trust (FC001000),and Cancer Research UK (FC001000)

By studying the roles of individual genes and cell populations in normal heart development, our work aims to provide a better understanding of the origins of cardiac malformations and how this complex organ is formed in the developing embryo. This may also contribute to our understanding of cardiac disease since accumulating evidence suggests that the same genes regulating normal heart development are important in both the normal and pathological adult heart phenotype. Since many of the basic steps in heart formation are similar in all vertebrates, valuable information can be obtained from studying a variety of different species. We are using transgenic and genomic methods to examine how gene expression is regulated in the developing heart of frog and mouse embryos and to assess their possible contribution to adult heart disease. Genome-wide chromatin immunoprecipitation methods and targeted gene manipulation are being used to study transcriptional regulation during heart development and to investigate transformations in heart structure and energetics at birth. 3D imaging and computer modelling procedures are being developed in parallel to provide systematic and quantitative ways to monitor effects of normal and altered gene expression on heart morphology and to identify novel roles of genes in cardiac morphogenesis.
Characterising the genetic programme regulating cardiogenesis is important not only for understanding of heart development, but also because several of the same transcriptional regulators are now implicated in cardiac pathologies and disease. The homeodomain protein NKX2-5 is an important early cardiac transcription factor implicated in many aspects of cardiogenesis including regulating the size and proliferation of cardiac precursor populations, terminal differentiation of the myocardium, establishment of the ventricular conduction system and postnatal conduction function. In humans, mutations in the NKX2-5 gene results in a spectrum of congenital heart disease of varying phenotypic penetrance, that is mirrored in mouse models. Despite its importance, remarkably little is known about the place of NKX2-5 in the cardiac genetic regulatory network and few direct target genes have been unambiguously identified.
The goal of our work is to identify direct target genes of NKX2-5 during cardiac development taking advantage of genomic resources and techniques for genome-wide analysis of transcription that have become available.We have combined microarray studies with genome-wide chromatin immunoprecipitation (ChIP) using heart tissue from mouse and frog embryos to identify putative target genes of NKX2-5 in the developing embryonic heart. Our work focuses on understanding the role of two of these: the proprotein convertase Furin and the ADP Ribosylhydrolase-like protein ADPRHL1. The former appears to mediate NKX2-5 function in both the early contribution of cells from the anterior heart field to the mid-gestation heart whilst the latter appears to be involved in the mechanics of chamber formation.

Publications

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