in neuron navigator 2 (NAV2), associated with smoking initiation. NAV2 has not previously been associated with substance use or addiction. Given its suspected involvement in neuronal growth and migration, a putatively causal nonsynonymous variant is a strong candidate for functional follow up experiments. Other genes implicated in the fine mapping analysis have less direct interpretations (e.g., HEATR5A) and such results will benefit from replication and/or follow-up experiments. In general, fine mapping studies narrowed the credible set of likely causal variants to single or double base pair resolution for 24 loci (Table S6). Some loci were not amenable to fine mapping, with credible intervals containing thousands of SNPs in some cases. Given the cost in money and time of conducting functional experiments at the cellular or organismal level, fine mapping likely causal variants can be extremely useful in predicting functional consequences and prioritizing variants for further work.
