Multifunctional roles of activins in the brain.

Activins, which are members of the TGF-β superfamily, were initially isolated from gonads and served as modulators of follicle-stimulating hormone secretion. Activins regulate various biological functions, including induction of the dorsal mesoderm, craniofacial development, and differentiation of numerous cell types. Activin receptors are highly expressed in neuronal cells, and activin mRNA expression is upregulated by neuronal activity. Activins also exhibit neuroprotective action during excitotoxic brain injury. However, very little is known about the functional roles of activins in the brain. We recently generated various types of transgenic mice, demonstrating that activins regulate spine formation, behavioral activity, anxiety, adult neurogenesis, late-phase long-term potentiation, and maintenance of long-term memory. The present chapter describes recent progress in the study of the role of activin in the brain.