Calcineurin A alpha (PPP3CA), calcineurin A beta (PPP3CB) and calcineurin B (PPP3R1) are located on human chromosomes 4, 10q21→q22 and 2p16→p15 respectively

Calcineurin (also called protein phosphatase-2B) is a calmodulin-regulated protein phosphatase which plays an important role in signal transduction. The enzyme is a heterodimer of a 58–59 kDa calmodulin-binding catalytic subunit (calcineurin A) and a small (i.e. 19 kDa) Ca2+-binding regulatory subunit (calcineurin B). The highly conserved calcineurin B is encoded by a single gene in all tissues except testes, whereas there are three isoforms of calcineurin A (α, β and γ) encoded by genes on three different chromosomes. This enzyme can play a critical role in transcriptional regulation and growth control in T lymphocytes by a mechanism believed to involve dephosphorylation of the nuclear factor NF-AT which is essential for transcription of the interleukin-2 gene. To better evaluate the potential role of the calcineurin genes in human genetic disorders, we have studied their chromosome locations. Calcineurin B (PPP3R1) is located on human chromosome 2p16→p15 and calcineurin Aβ (PPP3CB, previous gene symbol CALNB) is present on 10q21→q22. We confirm the localization of calcineurin Aα (PPP3CA, previous gene symbol CALNA) to chromosome 4 without regional localization.