AUTHOR=Woelfle Sarah , Boeckers Tobias M. 

TITLE=Layer-Specific Vesicular Glutamate Transporter 1 Immunofluorescence Levels Delineate All Layers of the Human Hippocampus Including the Stratum lucidum

JOURNAL=Frontiers in Cellular Neuroscience

VOLUME=15

YEAR=2021

URL=https://www.frontiersin.org/journals/cellular-neuroscience/articles/10.3389/fncel.2021.789903

DOI=10.3389/fncel.2021.789903

ISSN=1662-5102

ABSTRACT=<p>The hippocampal formation consists of the Ammon’s horn (<italic>cornu Ammonis</italic> with its regions CA1-4), dentate gyrus, subiculum, and the entorhinal cortex. The rough extension of the regions CA1-3 is typically defined based on the density and size of the pyramidal neurons without clear-cut boundaries. Here, we propose the vesicular glutamate transporter 1 (VGLUT1) as a molecular marker for the CA3 region. This is based on its strong labeling of the <italic>stratum lucidum</italic> (SL) in fluorescently stained human hippocampus sections. VGLUT1 puncta of the intense SL band co-localize with synaptoporin (SPO), a protein enriched in mossy fibers (MFs). Owing to its specific intensity profile throughout all hippocampal layers, VGLUT1 could be implemented as a pendant to Nissl-staining in fluorescent approaches with the additional demarcation of the SL. Furthermore, by high-resolution confocal microscopy, we detected VGLUT2 in the human hippocampus, thus reconciling two previous studies. Finally, by VGLUT1/SPO co-staining, we provide evidence for the existence of infrapyramidal MFs in the human hippocampus and we show that SPO expression is not restricted to MF synapses as demonstrated for rodent tissue.</p>