Homomeric nAChR subunits that do not have obligate partners might also lack positive pairwise correlations with other subunit genes. Several α-subunit genes had this property, including those known (Chrna7, Chrna9, and Chrna10) and others not yet known (Chrna1 and Chrna2) to form homomeric channels in brain (Gotti et al., 2006). Gene expression correlations across cell types recapitulated known nAChR receptor subunit combinations (Gotti et al., 2006) more accurately than correlations based on the bulk expression profiles for the nine regions (Figure S3B).
