VMAT2 is an integral membrane protein that acts to transport monoamines—particularly neurotransmitters such as dopamine, norepinephrine, serotonin, and histamine—from cellular cytosol into synaptic vesicles. In humans, the VMAT2 protein is encoded by the VMAT2 gene. Geneticist Dean Hamer identified the VMAT2 gene as correlating with spirituality using data from a smoking survey, which included questions intended to measure "self-transcendence". Hamer performed the spirituality study on the side, independently of the National Cancer Institute smoking study. His findings were published in the mass-market book According to Carl Zimmer, Hamer's study has not been academically published and depends on minor statistical variance.