ABSTRACT

Localization but Unknown Function ........................................................... 442 28.4.1 Neurotrypsin Mutation in Autosomal Recessive MR ..................... 443

28.5 What Do Nonsyndromic MR Genes Tell Us about the Cellular Mechanisms That Are Important for Cognitive Functions? ....................... 444

References.............................................................................................................. 445

Mental retardation (MR) is likely the result of alterations in molecular pathways underlying neuronal processes involved in cognitive functions; however, the exact nature of these pathways remains unknown. Remarkable progress in understanding the molecular and cellular basis of mental retardation has occurred in recent years. Genes associated with nonsyndromic mental retardation have been evaluated with regard to a role in synaptic transmission. Some of them have been linked to presynaptic vesicle release, whereas others are involved in the regulation of actin cytoskeleton dynamics via Rho GTPases. Detailed investigations of their molecular and cellular roles at the synapse may provide cues for synaptic mechanisms that are essential for cognitive functions.