HTRA2 and Parkinson disease: However, a neurodegenerative phenotype with parkinsonian features has been defined in Omi/HtrA2 knockout mice [74], and Strauss et al. performed a mutation screening of the Omi/HtrA2 gene in German Parkinson’s disease (PD) patients and identified a heterozygous G399S mutation in four (4/518) patients [75], which indicates that loss of function of Omi/HtrA2 in the central nervous system (CNS) may be linked to PD.