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Proc Natl Acad Sci U S A. 2003 Sep 30;100(20):11469-73. Epub 2003 Sep 18.

Evolutionary origins of the vertebrate heart: Specification of the cardiac lineage in Ciona intestinalis.

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  • 1Department of Molecular and Cell Biology, Division of Genetics and Development, Center for Integrative Genomics, University of California, Berkeley, CA 94720, USA. bandl@uclink.berkeley.edu

Abstract

Here we exploit the extensive cell lineage information and streamlined genome of the ascidian, Ciona intestinalis, to investigate heart development in a basal chordate. Several cardiac genes were analyzed, including the sole Ciona ortholog of the Drosophila tinman gene, and tissue-specific enhancers were isolated for some of the genes. Conserved sequence motifs within these enhancers facilitated the isolation of a heart enhancer for the Ciona Hand-like gene. Altogether, these studies provide a regulatory framework for the differentiation of the cardiac mesoderm, beginning at the 110-cell stage, and extending through the fusion of cardiac progenitors during tail elongation. The cardiac lineage shares a common origin with the germ line, and zygotic transcription is first detected in the heart progenitors only after its separation from the germ line at the 64-cell stage. We propose that germ-line determinants influence the specification of the cardiac mesoderm, both by inhibiting inductive signals required for the development of noncardiac mesoderm lineages, and by providing a localized source of Wnt-5 and other signals required for heart development. We discuss the possibility that the germ line also influences the specification of the vertebrate heart.

PMID:
14500781
[PubMed - indexed for MEDLINE]
PMCID:
PMC208781
Free PMC Article
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