Model of ERBB4 signaling in schizophrenia: a unique candidate target. (A) Schematic drawing of alternative ERBB4 splice variants. (B) Normal expression of ERBB4 isoforms. (C) Increased expression of ERBB4/CYT-1 isoforms in schizophrenia. (D) Specific inhibition of p110δ catalytical isoform of PI3K by IC87114 restores AKT activation. CRD, cysteine-rich domain; CYT, cytoplasmic isoform; JM, juxtamembrane isoform, TK, tyrosine kinase domain; TM, transmembrane domain.