KCNJ2 (Kir2.1 inward-rectifier potassium ion channel) is a potassium ion channel protein that maintains resting membrane potential and regulates cell excitability. It plays an important role in neural and craniofacial development. It is highly expressed in the hippocampus, nucleus accumbens, putamen and caudate in the brain as well as in skeletal muscle, and is central to the inward-rectifier current (IK1) that controls cardiac excitability in human ventricular muscle. Mutations in KCNJ2 affect neuronal excitability and are associated with Autism, short-QT syndrome and Andersen-Tawil syndrome. In immunohistochemistry, KCNJ2 has cytoplasmic positivity in most tissues throughout the body. References: Front. Cell. Neurosci. 2018, DOI: 10.3389/fncel.2018.00076; Heart Rhythm. 2005 Mar;2(3):316-24, PMID: 15851327; Cardiovascular Research. 2012. 93 (4): 666–673, DOI:10.1093/cvr/cvr329; J Physiol. 2016 Jun 15;594(12):3245-70, PMID: 26864374