Proteomic heterogeneity of glial cells of the central nervous system

Kaplan, Lew (2023): Proteomic heterogeneity of glial cells of the central nervous system. Dissertation, LMU München: Graduate School of Systemic Neurosciences (GSN)

Abstract

Mammalian brain and retina, both part of the central nervous system (CNS), contain a multitude of distinct glial cell populations. On a rough scale they can be categorized for example as oligodendrocytes, microglia and astroglia. While oligodendroglia are mostly absent from the eye, astrocytes line the inner surface of the retina and microglia reside between its nuclear layers. Most importantly, the retina has its own kind of specialized glial cells: Müller glia. These long cells are evenly distributed, span the whole thickness of the retina and fulfil similar homeostatic functions as astrocytes in the brain. As the CNS is divided in functional and anatomical subunits that additionally differ by species, the respective glia are also thought to vary in their duties. In this work I addressed the question which cellular functions are shared between, and which are specific for astroglial cells from different brain regions and retina. Additionally, Müller cell heterogeneity was under special scrutiny focusing on cells from the macular and peripheral human retina. As glial cells constitute only a subpopulation of all CNS cells, it was necessary to enrich our cells of interest to make the following analysis as precise as possible. We achieved this by magnetic bead associated cell sorting. These cell fractions were then subjected to tandem mass spectrometry and served as the basis of the subsequent work. To extract the information hidden in such complex datasets, I used various bioinformatics tools to break them down into smaller protein lists that allowed conclusions on their role in glial biology. Furthermore, I selected individual proteins for in-depth validation and functional examination. I identified transcription factors of the nuclear factor 1 family to be expressed across glial cells of all contemplated regions and species, which corroborated their reported role in gliogenesis of brain and retina. Several of the pathways with interregional differential expression, including candidate proteins SLMAP and ZEB1, converged onto Hippo pathway signaling and alternative splicing. Furthermore, Müller cells of the human macula displayed an increased expression of proteins of the extracellular matrix, cell adhesion and exosomal pathways hinting towards a shift in the extracellular milieu. In this context, I showed how EPPK1 might play a role in establishing the intricate Müller cell morphology, their biomechanical properties and the secretion of extracellular vesicles. Finally, the proteomic datasets generated as part of my thesis have expanded our understanding of the biology of glia in different regions of the CNS and the retina specifically. The present findings will help to better understand the regional adaptions of astrocytes and Müller cells allowing the development of better tools or treatments targeting the desired subpopulations and translate insights between them.

• Dokumententyp: Dissertationen (Dissertation, LMU München)
• Keywords: Glia, Müller cells, retina, proteomics, central nervous system
• Themengebiete: 500 Naturwissenschaften und Mathematik ; 500 Naturwissenschaften und Mathematik > 570 Biowissenschaften, Biologie
• Fakultäten: Graduate School of Systemic Neurosciences (GSN)
• Sprache der Hochschulschrift: Englisch
• Datum der mündlichen Prüfung: 8. Mai 2023
• 1. Bericht­erstatter:in: Grosche, Antje