CB1 receptor gene expression changes across brain development and is altered in schizophrenia, with COMT genotype modifying the trajectory

CNR1 expression is high in fetal prefrontal cortex and hippocampus, then drops dramatically after birth. The lifespan trajectory of CNR1 in DLPFC was modified by COMT Val158Met genotype: valine carriers showed stronger age-related decline. CNR1 methylation at cg02498983 increased with age (inversely correlated with expression) and was strongest in valine carriers. CNR1 was decreased in schizophrenia DLPFC but upregulated in schizophrenia suicide victims. THC and ethanol were each associated with dysregulated CNR1 in affective disorder PFC. A novel CNR1 transcript was predicted by SNP rs806368.

Postmortem human brain tissue analysis of CNR1 mRNA expression and DNA methylation across prefrontal cortex, hippocampus, and caudate from developmental samples and schizophrenia cases. eQTL analysis and COMT genotype interaction testing.

Published in Translational Psychiatry, this maps the CB1 receptor across the human lifespan and shows that both genetic variation (COMT) and environmental exposure (THC) interact to determine CB1 expression. This gene-by-environment framework helps explain why adolescent cannabis use specifically increases psychosis risk.

The COMT genotype interaction explains individual vulnerability: some people (Val/Val carriers) may have CB1 receptors that are more sensitive to age-related decline and potentially more susceptible to cannabis-induced disruption during adolescence, when the developmental trajectory is most dynamic.

Postmortem tissue (cannot determine temporal sequences in living brain); relatively small samples per condition; medication effects not fully controlled; COMT genotype analysis limited to Caucasian subjects; cannot determine if CNR1 changes cause or result from schizophrenia.