HTRA2 (Omi, Prss25, mnd2) is a mitochondrial serine protease protease that regulates mitochondrial homeostasis and molecular quality control and is involved in caspase-dependent apoptosis. HTRA2 dysfunction or mutation is implicated in the pathogenesis of neurodegenerative syndromes such as Parkinson’s disease and neuromuscular disorders and juvenile lethality in mice. HTRA2 is also differentially expressed expressed in various cancers relative to normal tissue and is thought to be involved in tumorigenesis. In immunohistochemistry of normal tissue, HTRA2 has cytoplasmic positivity in a majority of tissues throughout the body. References: Int J Cell Biol. 2012;2012:607929, PMID: 22675361; Nature. 2003 Oct 16;425(6959):721-7, PMID: 14534547; APMIS. 111 (5): 586–90, PMID: 12887511;