Role of Homeobox Gene Nkx2-5 in Heart Development and Congenital Heart Disease

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This project seeks to define the developmental principles underlying chamber formation in the developing heart and how this becomes abnormal in inherited heart defects. The gene we study, Nkx2-5, encodes a protein which binds to DNA and regulates the expression of the genetic program for formation of the ventricles, the pumping chambers of the heart. We believe that Nkx2-5 is an Oexecutive regulator? of this program, controlling the timing and spatial expression of other regulators that then control expression of a host of genes required for muscle differentiation and the development of form (morphogenesis). Mutations in one copy of the human Nkx2-5 gene have recently been discovered to be associated with atrial septal defect, or Ohole in the heartO, a sometimes serious inherited defect in heart structure. Mouse embryos with a mutation in both copies of the gene have a much more serious defect in ventricle formation that is incompatible with life. The studies are designed to extend our understanding of the genetic regulation of chamber formation in the heart. We will firstly make a mouse model of the human disease using gene targeting technology, which allows us to make precise alteration in single genes in this animal. Secondly, we will apply new technology to the heart that will let us visualise molecular and cellular events at higher resolution. This technology, which uses fluorescent tags on cells and a laser to measure cell identity, has been used to great affect in the field of immunology, but can be adapted to the heart. We will use it to isolate and characterise the precious early cells that give rise to the heart in the embryo. It is in these cells that the human and mouse mutations have their first effects. Our studies have relevance to understanding and screening for human inherited heart abnormalities, and for understanding the general principles of heart formation that may reveal valuable ways to intervene in heart disease.