CNS hypomyelinated mutant mice (jimpy, shiverer, quaking): in vitro evidence for primary oligodendrocyte defects

Vertebrate mutations contribute to the analysis of cell interactions in nervous system development. In this symposium, Tompkins will describe grafting of cells with new visualizable genetic markers into histocompatible recipients in Xenopus laevis. This allows the fate of cells to be traced with great precision in relation to connectivity pasterns in developing and mature chimeric brains. Crepel uses mutant mice and x-irradiated rats to explore, with physiological and anatomical methods, the developmental relationships between cerebellar climbing fiber inputs and their Purkinje cell targets. He will describe mechanisms involved in the transition from an initial high innervation ratio to the approximately i:i ratio of the adult, with particular ~mphasis on control by the posts>~aptic cell. The second half of the symposium focuses on the shiverer(shi) mutations in the mouse. The shi locus controls myelin basic protein(MBP) and offers a special opportunity for coordinating results obtained by the methods of molecular genetics and developmental biology. Carson will review his evidence for coordinate genetic control of the several mouse low molecular weight MBP's and will indicate status of efforts to clone the shi gene. Wolf will show through confrontation of mutant and wildtype cells in organotypic culture that the shi locus affects myelinatlon by action in the oligodendrological cell and not in the related axon.