TMEM119

TMEM119 is a gene that encodes a transmembrane protein expressed primarily by microglia in the mammalian brain. It has become a widely used molecular marker for identifying resident microglia in research because its expression is largely restricted to microglial cells within the central nervous system and is not found in circulating monocytes or most other brain macrophages.

In practice, TMEM119 is used to distinguish microglia from infiltrating peripheral immune cells in studies of brain development, aging, injury, and neurodegenerative disease. It is detected with immunohistochemistry and flow cytometry, often in combination with other microglia markers such as P2RY12 or CX3CR1 to improve specificity and interpretation.

Expression of TMEM119 is typically robust in homeostatic microglia, but some studies indicate that Levels can be influenced by disease states or inflammatory conditions, which may affect marker-based identification. As a result, researchers often validate TMEM119-based findings with additional markers and methods to account for potential variability in expression.

The precise biological function of the TMEM119 protein remains incompletely understood. While its membrane localization suggests a role in cell-surface signaling or interactions, definitive experimental evidence defining its functional contributions to microglial biology is still developing. In summary, TMEM119 serves as a useful microglia-specific marker in human and mouse CNS research, aiding the distinction between resident microglia and infiltrating macrophages, with ongoing work to clarify its functional role.