F-spondin and mindin: two structurally and functionally related genes expressed in the hippocampus that promote outgrowth of embryonic hippocampal neurons

Extracellular matrix (ECM) proteins play an important role in early cortica l development, specifically in the formation of neural connections and in c ontrolling the cyto-architecture of the central nervous system, F-spondin a nd Mindin are a family of matrix-attached adhesion molecules that share str uctural similarities and overlapping domains of expression. Genes for both proteins contain a thrombospondin type I repeat(s) at the C terminus and an FS1-FS2 (spondin) domain. Both the vertebrate F-spondin and the zebrafish mindins are expressed on the embryonic floor plate. In the current study we have cloned the rat homologue of mindin and studied its expression and act ivity together with F-spondin in the developing rodent brain. The two genes are abundantly expressed in the developing hippocampus, In vitro studies i ndicate that both F-spondin and Mindin promote adhesion and outgrowth of hi ppocampal embryonic neurons. We have also demonstrated that the two protein s bind to a putative receptor(s) expressed on both hippocampal and sensory neurons.