More specifically, through the use of digital droplet polymerase chain reactions and analysis of single nucleotide polymorphism (SNP) data, overexpression of C4 (originating from the MHC locus), particularly the C4A gene, has been linked with increased schizophrenia risk, with C4A mRNA being elevated in post-mortem brain tissue from schizophrenic patients (15). The gene discussed is C4A; the disease is schizophrenia.