Metastasis-associated mts1 (S100A4) protein is selectively expressed in white matter astrocytes and is up-regulated after peripheral nerve or dorsal root injury.

The S100 family of calcium binding proteins has been shown to be involved in a variety of physiological functions, such as regulation of enzyme function, cell motility, modification of extracellular matrix, and cell proliferation. Several members of the S100 family are expressed in the nervous system, but their functional roles are still largely obscure. The Mts1 gene codes for the S100A4 protein, which has been implicated in the control of cell proliferation and metastasis activity of tumor cells. We have used immunohistochemistry to examine the expression pattern of the Mts1 protein in the adult rat spinal cord and how this expression is influenced by peripheral nerve or dorsal root injury. Mts1 immunoreactivity (IR) was present only in white matter astrocytes in the intact spinal cord. Sciatic nerve as well as dorsal root injury induced a marked and prolonged up-regulation of Mts1-IR in astrocytes in the region of the dorsal funiculus containing the central processes of the injured primary sensory neurons. These findings suggest that Mts1 plays a unique physiological role in white matter astrocytes as well as in the response of astrocytes to degeneration of myelinated axons.