The protein encoded by ANKK1, a member of the receptor interacting protein serine/threonine kinases, is believed to play a role in signal transduction that includes activation of transcription factors in response to environmental factors.54 ANKK1 is reportedly expressed in radial glia during development and in astrocytes within the adult brain.55 ANKK1 expression is upregulated by administration of apomorphine, a dopamine agonist, and is temporally associated with DRD2 expression in developing mice.54–56 These findings, coupled with the genes’ proximity, have led investigators to posit that the protein encoded by ANKK1 may play an important role in the alterations in dopaminergic signaling following drug exposure central to the addiction process.54 TTC12, also expressed in the brain, contains a tetratricopeptide repeat structure known to facilitate protein-protein binding and for which effects on steroid hormone receptors have been reported.57 Further investigation will be necessary to characterize more clearly the roles these genes may play in the pathophysiology of illicit drug dependence.
