MOLECULAR-CLONING OF TOPAP - A TOPOGRAPHICALLY GRADED PROTEIN IN THE DEVELOPING CHICK VISUAL-SYSTEM

Topographically graded molecules representing position-specific differ ences among otherwise similar cells are thought to play a role in the patterning of the developing nervous system. In the embryonic chick vi sual system, a 40 kDa protein, TOPAP, is expressed in a posterior > an terior gradient in the retina and in an inverted anterior > posterior gradient in the optic tectum, the major retinal projection area. Here we report the isolation and nucleotide sequencing of a complementary D NA clone encoding the chick TOPAP protein and demonstrate that the mRN A encoding this coiled-coil integral membrane protein is topographical ly graded within the retina and is present in a variety of chick tissu es.