Molecular Diversity Among Adult Hippocampal and Entorhinal Cells

The hippocampal-entorhinal system is comprised of functionally distinct subregions collectively critical for cognition, and selectively vulnerable to aging and pathological processes. To gain insights into neuronal and non-neuronal populations within this system, we performed single-nucleus transcriptional profiling from five human hippocampal-entorhinal subregions. We found that transcriptomic diversity of excitatory neurons across these subregions reflected the molecular transition from three-layered archicortex to six-layered neocortex. Additionally, mRNA and protein for DCX, an immature neuron marker, were clearly detected in some cells, but not in dentate granule cells, the cell-type predicted to be generated in adult neurogenesis. We also found that previously functionally uncharacterized METTL7B was enriched in human and non-human primate neuronal subtypes less vulnerable to initial Alzheimer9s disease pathology. Proteomic and biochemical assays revealed METTL7B interacts with Alzheimer9s disease-related proteins, including APP, and its overexpression reduced amyloid-beta generation. These results reveal cell type-specific molecular properties relevant for hippocampal-entorhinal physiology and dysfunction.