For example, MAO-A mRNA is repressed across cancers, yet MAO-A protein and levels of serotonin, a substrate of MAO-A implicated in depression, are paradoxically increased in malignancies, including breast cancer.
The frontal abnormality of patients with depression had certain 5-HT genetic basis, and 5-HT2A receptor CC allele and MAOA-H genotype had synergistic effect on the activity abnormality when recognizing negative emotion in right frontal middle gyrus of patients with depression.
Monoamine oxidase A (MAOA), a mitochondrial enzyme involved in the degradation of amines, has been reported to be associated with aggression, impulsivity, depression, and mood changes.
Molecular genetic studies point to potential risk loci of psychotic depression shared with schizoaffective disorder (1q42, 22q11, 19p13), depression, bipolar disorder, and schizophrenia (6p, 8p22, 10p13-12, 10p14, 13q13-14, 13q32, 18p, 22q11-13) and several vulnerability genes possibly contributing to an increased risk of psychotic symptoms in depression (eg, BDNF, DBH, DTNBP1, DRD2, DRD4, GSK-3beta, MAO-A).