Habenular expression of rare missense variants of the ?4 nicotinic receptor subunit alters nicotine consumption.

ABSTRACT: The CHRNA5-CHRNA3-CHRNB4 gene cluster, encoding the ?5, ?3, and ?4 nicotinic acetylcholine receptor (nAChR) subunits, has been linked to nicotine dependence. The habenulo-interpeduncular (Hb-IPN) tract is particularly enriched in ?3?4 nAChRs. We recently showed that modulation of these receptors in the medial habenula (MHb) in mice altered nicotine consumption. Given that ?4 is rate-limiting for receptor activity and that single nucleotide polymorphisms (SNPs) in CHRNB4 have been linked to altered risk of nicotine dependence in humans, we were interested in determining the contribution of allelic variants of ?4 to nicotine receptor activity in the MHb. We screened for missense SNPs that had allele frequencies >0.0005 and introduced the corresponding substitutions in Chrnb4. Fourteen variants were analyzed by co-expression with ?3. We found that ?4A90I and ?4T374I variants, previously shown to associate with reduced risk of smoking, and an additional variant ?4D447Y, significantly increased nicotine-evoked current amplitudes, while ?4R348C, the mutation most frequently encountered in sporadic amyotrophic lateral sclerosis (sALS), showed reduced nicotine currents. We employed lentiviruses to express ?4 or ?4 variants in the MHb. Immunoprecipitation studies confirmed that ?4 lentiviral-mediated expression leads to specific upregulation of ?3?4 but not ?2 nAChRs in the Mhb. Mice injected with the ?4-containing virus showed pronounced aversion to nicotine as previously observed in transgenic Tabac mice overexpressing Chrnb4 at endogenous sites including the MHb. Habenular expression of the ?4 gain-of-function allele T374I also resulted in strong aversion, while transduction with the ?4 loss-of function allele R348C failed to induce nicotine aversion. Altogether, these data confirm the critical role of habenular ?4 in nicotine consumption, and identify specific SNPs in CHRNB4 that modify nicotine-elicited currents and alter nicotine consumption in mice.

SUBMITTER: Slimak MA 

PROVIDER: S-EPMC3902282 | biostudies-literature | 2014

REPOSITORIES: biostudies-literature