PTPRN2 and mood disorder: Although the function of phogrin in nerve cells remains poorly understood, phogrin disruptions have been linked to attention deficits (Lionel et al., 2011), addiction and mood disorders (Yang et al., 2011), Down Syndrome (Papoulidis et al., 2014) and HOXA1 spectrum disorder (Abu-Amero et al., 2012) suggesting a pivotal role in regulating brain development and function.