Grabel 9604367 The long term goals of this investigation are to identity the genes involved in making, early lineage decisions during mammalian embryogenesis and to define how the products of these genes interact. Dr. Grabel propose that the Indian hedgehog (Ihh) gene is involved in initiating both extraembryonic endoderm and mesoderm differentiation. Evidence accumulated by us using the P9 teratocarcinoma system, as well as ES cells and mouse blastocyst cultures, suggests a role for Ihh in establishing extraernbryonic endoderm. Proposed studies will substantiate this role, begin to define the molecular mechanism of action of Ihh in early mouse embryogenesis, and determine if mesoderm induction involves Ihh action. Specific Aims are: 1. To substantiate the role of Ihh in extraembryonic endoderm differentiation. These studies will include situ hybridization analyses and immunocytochemistry, generating an Ihh-deficient P9 cell line by targeted mutagenesis, and testing the effect of hh peptides. 2. To identify gene products involved in the hh signaling pathway active during early mouse embryogenesis. These studies will test the role of the patched (ptc) gene and of protein kinase A as downstream mediators of Ihh. 3. To determine if Ihh provides a signal that acts via BMP-2 or BMP-4 to induce mesoderrn. Hedgehog genes clearly play a critical role in patterning the embryo. These studies promise to define the role of Ihh in signaling the earliest lineage decision in the mammalian embryo, distinguishing embryonic from extraembryonic and establishing primary germ layers.
