"Elucidating the Function of Syndecan in CNS Development"
 Karl G. Johnson, Pomona College, Claremont CA 91711

Heparan sulfate proteoglycans (HSPGs) are a diverse family of extracellular matrix proteins that regulate axon guidance and synapse formation in a variety of vertebrate and invertebrate species.  We have recently demonstrated that despite overlapping expression patterns and similar carbohydrate sidechains, these HSPGs exhibit remarkable core-protein specificity.  The transmembrane HSPG Syndecan promotes synapse growth and proper axon guidance at the CNS midline, while the GPI-anchored HSPG Dallylike inhibits synapse growth and plays no obvious role in midline guidance.  Yet, the molecular mechanisms of HSPG function remain poorly understood.  We conducted a yeast two-hybrid screen with the cytoplasmic domain of Syndecan and have identified five candidate proteins that may function downstream of Syndecan during these processes.  Characterizing phenotypes for these mutants will further our understanding of the molecular mechanisms not only of axon guidance at the CNS midline, but also of synaptic assembly.

Karl G. Johnson, Ph.D.
Assistant Professor of Biology and Neuroscience
Pomona College
175 West 6th Street
Claremont, CA 91711
Phone: (909) 607-0069  
Fax: (909) 621-8878