The establishment of topographic projections in the developing visual system depends on the spatially and temporally controlled expression of axon guidance molecules. In the developing chick tectum, the graded expression of the repulsive guidance molecule (RGM) has been proposed to be involved in controlling the topography of the retinal ganglion cell (RGC) axon termination zones along the anteroposterior axis of the tectum. We now show that there are three mouse proteins homologous to chick RGM displaying similar proteolytic processing but exhibiting differential cell-surface targeting by glycosyl phosphatidylinositol anchor addition. Two members of this gene family (mRGMa and mRGMb) are expressed in complementary patterns in the nervous system, and mRGMa is expressed prominently in the superior colliculus at the time of anteroposterior targeting of RGC axons. The third member of the family (mRGMc) is expressed almost exclusively in skeletal muscles. Functional studies in the mouse reveal a role for mRGMa in controlling cephalic neural tube closure, thus defining an unexpected role for mRGMa in early embryonic development. In contrast, mRGMa mutant mice did not exhibit defects in anteroposterior targeting of RGC axons to their stereotypic termination zones in the superior colliculus.
SciCrunch is a data sharing and display platform. Anyone can create a custom portal where they can select searchable subsets of hundreds of data sources, brand their web pages and create their community. SciCrunch will push data updates automatically to all portals on a weekly basis. User communities can also add their own data to scicrunch, however this is not currently a free service.