CHRNA5 and schizophrenia: Given the association of TCF4 common variants with schizophrenia, we initially focused on TCF4 binding sites in schizophrenia risk loci identified in the most comprehensive genome wide association study published to date.4 Although there was only nominal enrichment of TCF4 targets among the genome-wide significant schizophrenia loci, many schizophrenia susceptibility loci contain functional TCF4 binding sites such as the CHRNA5/A3/B4 locus which encodes subunits of the nAChR.