A case in point is aphakia mice, which have a spontaneous mutation in the Pitx3 transcription factor gene, that results in selective developmental loss of nigrostriatal dopamine neurons and an ~90% reduction in dorsal striatal dopamine (Hwang et al., 2003; Nunes et al., 2003; van den Munckhof et al., 2003; Smidt et al., 2004). This evidence concerns the gene PITX3 and lens disorder.