Another possible cause of ALS is gene defects. The possible genetic contribution to the development of ALS is an active research area. 10% of ALS is inherited, and twenty percent of these patients carry a common mutation in the Superoxide Dismutase Gene (SOD1). Additionally, other genetic factors play a role in the cause of ALS. One such factor is the level of the protein VEGF (vascular endothelial growth factor) that is made depending on the structure of a persons VEGF gene. Another genetic factor recently implicated is the gene for the iron processing protein HFe. Other factors include how the genetic message (mRNA) for the glutamate transport protein is processed and the presence of mutations in the gene for the structural protein called neurofilament.