Rab6A as a Pan-Astrocytic Marker in Mouse and Human Brain, and Comparison with Other Glial Markers (GFAP, GS, Aldh1L1, SOX9)

Abstract

Astrocytes contribute to many higher brain functions. A key mechanism in glia-to-neuron signalling is vesicular exocytosis; however, the identity of exocytosis organelles remains a matter of debate. Since vesicles derived from the trans-Golgi network (TGN) are not considered in this context, we studied the astrocyte TGN by immunocytochemistry applying anti-Rab6A. In mouse brain, Rab6A immunostaining is found to be unexpectedly massive, diffuse in all regions, and is detected preferentially and abundantly in the peripheral astrocyte processes, which is hardly evident without glial fibrillary acid protein (GFAP) co-staining. All cells positive for the astrocytic markers glutamine synthetase (GS), GFAP, aldehyde dehydrogenase 1 family member L1 (Aldh1L1), or SRY (sex determining region Y)-box 9 (SOX9) were Rab6A+. Rab6A is excluded from microglia, oligodendrocytes, and NG2 cells using cell type-specific markers. In human cortex, Rab6A labelling is very similar and associated with GFAP+ astrocytes. The mouse data also confirm the specific astrocytic labelling by Aldh1L1 or SOX9; the astrocyte-specific labelling by GS sometimes debated is replicated again. In mouse and human brain, individual astrocytes display high variability in Rab6A+ structures, suggesting dynamic regulation of the glial TGN. In summary, Rab6A expression is an additional, global descriptor of astrocyte identity. Rab6A might constitute an organelle system with a potential role of Rab6A in neuropathological and physiological processes.

Evolution of glial cells: a non-bilaterian perspective

“…2). A metabolic enzyme, Aldh1l1 (aldehyde dehydrogenase 1 family member L1), and intracellular signaling Rab6 are pan-astrocytic markers in rodents [47,48]. Some of these markers, especially those involved in glutamate metabolism, have been successfully used to identify glial presence in invertebrate bilaterians, e.g., planarians [25].…”

The RNA‐binding protein and stress granule component ATAXIN‐2 is expressed in mouse and human tissues associated with glaucoma pathogenesis

“…Glutamine synthetase (GS) antibody (Santa Cruz Biotechnology; RRID: AB_641095) was raised in goat against the C-terminal peptide of human origin and corresponds to a ~42 kDa Western blot product. The antibody shows reactivity with mouse and human peptide, among numerous other species, and is a specific marker for Müller glia in mouse and human retina (Bastone et al, 2009;Jager et al, 2020;Melzer et al, 2021).…”