Organism-wide mapping of MHC class I and II expression in mouse lemur cells and tissues

The major histocompatibility complex (MHC) class I and II glycoproteins have been associated with numerous disease phenotypes, mechanisms and outcomes. These associations can be due to allotypic polymorphism or to altered levels of allotype expression. Although well studied in a range of cell types and microenvironments, no study has encompassed all cell-types present in an individual mouse lemur. In this study the droplet-based single cell RNA sequence data from the mouse lemur cell atlas, Tabula Microcebus, were used to examine the patterns of MHC class I and II expression. The cell atlas comprises data obtained from 27 organs from four mouse lemurs, enabling comparison of expression pattern between both cell types and the individual lemurs. Patterns of gene expression showed a good concordance among the four mouse lemurs. Three primary patterns of expression were identified and associated with different cell-types. Mapping MHC expression onto existing cell trajectories of cell development and spatial gradients revealed fine scale differences in expression level and pattern in single tissues. The bioinformatic pipeline developed here is applicable to other cell atlas projects.