NRG1 and schizophrenia: Neuregulin-1 (NRG1) is a gene that has been associated with increased risk for schizophrenia across diverse populations.1–3 Studies on postmortem brain and serum from schizophrenia cases have reported up-regulation of specific NRG1/ErbB4 splice variants and increased NRG1 signaling,4–9 and decreased isoform-specific expression of NRG1 transcripts.9,10 However, despite such combined genetic and pathologic evidence for NRG1 dysregulation in schizophrenia, the mechanisms underlying this association remain unclear.11