Heparin-binding EGF-like growth factor is required for synaptic plasticity and memory formation

Heparin-binding epidermal growth factor-like growth factor (HB-EGF), a member of epidermal growth factor (EGF) family, is a potent mitogenic peptide for various types of cells. HB-EGF is widely expressed in central nervous system, including hippocampus and cerebral cortex, and is considered to play pivotal roles in the developing and adult nervous system. In this study, we assessed the role of HB-EGF in learning and memory by testing HB-EGF conditional knock-out mice (KO) in two different learning tasks, and evaluated the long-term potentiation (LTP) in hippocampus slices from these mice. The HB-EGF KO mice were impaired in spatial memory in the Morris water maze and in fear learning in a passive avoidance test. HB-EGF KO mice also showed an impaired LTP, and reduction in activity of Ca ²⁺/calmodulin-dependent protein kinase II (CaMKII) and phosphorylated GluR1. We also found that the levels of neurotrophic factors, such as nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), neurotrophin-3 (NT-3), or glial cell line-derived neurotrophic factor (GDNF), were altered in several brain regions in the HB-EGF KO mice. These results confirm the importance of the HB-EGF in synaptic plasticity and memory formation.