Anterior endoderm is sufficient to rescue foregut apoptosis and heart tubemorphogenesis in an embryo lacking retinoic acid

The vitamin A deficient (VAD) quail embryo lacks active retinoids, fails to express normally GATA-4, and develops a nonlooping heart tube morphogeneti c defect that is a model for congenital cardiomyopathy. VAD quail embryos, or chick embryos depleted specifically for GATA factors, show in addition a bnormal foregut development, characterized by apoptosis of the endoderm cel ls associated with presumptive myocardium during the process of heart tube formation. Exogenous retinoic acid or transplantation of normal chick embry o anterior endoderm is sufficient to rescue apoptosis as well as GATA-4 exp ression and results in normal development and heart tube morphogenesis. Nor mal posterior endoderm also contains retinoids but is unable to rescue the VAD defect. Our results indicate that a retinoid-dependent transcriptional program, mediated at least in part by GATA factors, is critical in presumpt ive foregut endoderm for normal heart tube morphogenesis. (C) 2000 Academic Press.