CASP9 (Caspase 9) is a cysteine-aspartic acid protease involved in the execution-phase of cell apoptosis. CASP9 plays a central role in apoptosis and is considered a tumor suppressor. It is important for development of the central nervous system, and absence or mutation of CASP9 leads to abnormal development including neural tube defects, abnormal function and premature death. CASP9 is implicated in the progression of various neurodegenerative diseases including Alzheimer’s, Huntington’s, Parkinson’s and amyotrophic lateral sclerosis (ALS). It can be upregulated in the brain of Alzheimer’s patients. In immunohistochemistry, CASP9 has highest cytoplasmic and nuclear positivity in the brain and heart, medium expression in the liver, pancreas and skeletal muscle, and lowered positivity in all other tissues. References: The International Journal of Biochemistry & Cell Biology. 32 (2): 121–4, PMID: 10687948; Circulation Research. 99 (4): 415–23, PMID: 16857965; Journal of Neuroscience. 2010. 30 (7) 2623-2635; DOI: JNEUROSCI.5115-09.2010; CNS Neurosci Ther. 2018 May;24(5):394-403, PMID: 29365368