Identification of molecules and mechanisms involved in pattern formation in embryonic development has been a central problem of developmental biology. Recently, studies of homeobox genes and retinoic acid have brought exciting new insights to the understanding of pattern formation. Dr. Chuong has recently found homeoprotein gradients in developing feather buds and position specific homeoprotein expression patterns in different cutaneous appendages. He also has showed retinoic acid causes a disorientation of feather axes and converted feathers into scale- like structures in a concentration dependent manner. He hypothesizes that Hox gene expression is involved in determining the phenotypes and orientation of cutaneous appendages in birds as has been found for appendage phenotypes in Drosophila. He will examine the distribution of the Hox 4 complex during feather morphogenesis. He will analyze the effect of a retinoic acid gradient on feather pattern formation by arranging retinoic acid soaked beads in a geometric pattern on cultured feather explants. The function of the homeoprotein gradient will be tested directly by disrupting the gradients with ectopically expressed Hox genes. This work will combine classical feather morphogenesis experiments with modern molecular biology and offers an excellent opportunity to provide clear answers to some fundamental issues of morphogenesis.
