SEMA4B and injury: Sema4B is a transmembrane type 4 semaphorin, which has been suggested to be expressed in astrocytes (Liu et al., 2006; Lovatt et al., 2007; Cahoy et al., 2008; Maier et al., 2011); however, the role of the Sema4B gene in astrocytes following brain injury is not known.