Beyond a proposed general role of axonal guidance pathways in the development of neurodegeneration [16], [17], it is interesting to note that PLXNA4 can be place into a network containing several firmly established PD genes (SNCA, PARK2, DJ-1, LRRK2), although both known and less reliable projected interactions have to be utilized (Figure 4). The gene discussed is PLXNA4; the disease is Parkinson disease.