Cellular expression of the K+-Cl- cotransporter KCC3 in the central nervous system of mouse.

Potassium/Chloride cotransporters are transmembrane proteins that regulate cell volume and control neuronal activity by transporting K(+) and Cl(-) ions across the plasma membrane. Potassium/Chloride cotransporter 3 (KCC3) mutations are responsible for hereditary motor and sensory neuropathy with agenesis of the corpus callosum (HMSN/ACC), which is a severe sensory and motor neuropathy. Two major splice variants, KCC3a and KCC3b, were shown to be expressed in adult mouse tissues. Although KCC3a is mainly expressed in the central nervous system (CNS), its specific cellular expression patterns have not been determined. Here, we used an approach combining in situ hybridization and immunohistochemical techniques to determine the cellular expression of KCC3 in the mouse CNS and showed that KCC3 is mainly expressed in neurons, including a subpopulation of interneurons. Finally, we showed that some non-neuronal cells, such as radial glial-like cells in the spinal cord, also express KCC3.