dnPAK transgenic mice have a mouse calcium/calmodulin-dependent protein kinase II alpha (Camk2a) promoter directing postnatal forebrain expression of the mouse dominant negative (dn) autoinhibitory domain (AID) of p21 protein (Cdc42/Rac)-activated kinase (Pak) gene (dnPAK). The AID is conserved in all three Pak genes (Pak1, Pak2, Pak3). Homozygous dnPAK mice are viable, fertile, and normal in size. Pak genes are expressed in multiple brain regions, including the cortex and hippocampus, and are critical regulators of actin remodeling. The activation of PAK catalytic activity requires the release of the catalytic domain from the AID and autophosphorylation of a gene specific threonine residue. dnPAK binds to the catalytic domain of PAK and blocks autophosphorylation, inhibiting activation of catalytic activity. dnPAK overexpression causes a decrease in the number of and increase is the size of cortical neuron dendritic spines. Also observed is an increase in the proportion of larger synapses. These cortical neurons exhibit impaired bidirectional modifiability of synaptic strength with enhanced long-term potentiation (LTP) and reduced long-term depression (LTD), leading to a deficit in consolidation and retention of spacial memory. These mice may be useful for studying the regulation of synaptic structure and strength, and dendritic spine morphogenesis associated with the causes of mental retardation, fragile X syndrome, and autism.
