GPRC6A and Infertility: Notably, some genetic evidence does support a role of the putative OCN receptor GPRC6A in reproduction as illustrated by two studies linking mutations in GPRC6A to sub-/infertility in males.110,122 Although the significance of these studies is limited by their small sample sizes, experimental data suggests that these phenotypes may indeed be attributable to impaired OCN signaling.122 Yet, a potential involvement of other GPRC6A ligands cannot be definitely excluded at this point.