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Mice lacking the hypoxia responsive element in the promoter of vascular endothelial growth factor (VEGF) develop a phenotype with weakness and pathological reflexes that resemble amyotrophic lateral sclerosis (ALS). A subsequent study demonstrated an association between polymorphisms in the promoter of VEGF and ALS in humans. Therefore other angiogenic genes were investigated in ALS, which showed mutations in angiogenin (ANG) in patients with familial and sporadic ALS.1 A recent study confirmed this association and also demonstrated that ANG mutations predispose to Parkinson's disease (PD).2 The association with PD has independently been replicated.
It is not known how mutations in ANG lead to neurodegeneration. The ANG protein is involved in the transcription of ribosomal DNA, RNA metabolism, neurite outgrowth and axonal pathfinding. Cell survival assays show that wild type ANG is capable of rescuing cells containing ANG mutations from death when challenged with toxic agents, suggesting ANG is a potent neuroprotective factor.3 Functional studies have demonstrated that most mutations result in a loss of function.3
A small study demonstrated elevated serum ANG levels in patients with ALS,4 which could however not be replicated in a later study.5 Here, we compared serum ANG levels in a large cohort of patients with ALS and PD with controls.
Two hundred and sixty-five serum samples were available from patients with sporadic ALS, all of which were referred to the University Medical Center Utrecht (UMCU) and diagnosed according to the revised El Escorial criteria. One hundred and sixty-three serum samples were available from patients …