SORT1 and Tremor: While further research is still required, given the role of sortilin downregulation and p75NTR upregulation in central nervous system impairment and neurodegeneration (Harrington et al., 2004; Jansen et al., 2007; Willnow et al., 2008) and taking into account that changes in the expression level of p75NTR are correlated with functional changes in the GABAergic inhibitory neurotransmission (Blaesse et al., 2009), we hypothesize that the sortilin deficiency caused by the SORT1 p.G171A mutation may lead to defects in neurotransmission, giving rise to the development of tremor.