Spatial-Temporal Expression of Non-classical MHC Class I Molecules in the C57 Mouse Brain.

Recent studies clearly demonstrate major histocompatibility complex (MHC) class I expression in the brain plays an important functional role in neural development and plasticity. A previous study from our laboratory demonstrated the temporal and spatial expression patterns of classical MHC class I molecules in the brain of C57 mice. Studies regarding non-classical MHC class I molecules remain limited. Here we examine the expression of non-classical MHC class I molecules in mouse central nervous system (CNS) during embryonic and postnatal developmental stages using in situ hybridization and immunofluorescence. We find non-classical MHC class I molecules, M3/T22/Q1, are expressed in the cerebral cortex, neuroepithelium of the lateral ventricle, neuroepithelium of aquaeductus and developing cerebellum during embryonic developmental stages. During the postnatal period from P0 to adult, non-classical MHC class I mRNAs are detected in olfactory bulb, hippocampus, cerebellum and some nerve nuclei. Overall, the expression patterns of non-classical MHC class I molecules are similar to those of classical MHC class I molecules in the developing mouse brain. In addition, non-classical MHC class I molecules are present in the H2-K(b) and H2-D(b) double knock-out mice where their expression levels are greatly increased within the same locations as compared to wild type mice. The elucidation and discovery of the expression profile of MHC class I molecules during development is important for supporting an enhanced understanding of their physiological and potential pathological roles within the CNS.