Translatomic database of cortical astroglia across male and female mouse development reveals two distinct developmental phenotypes

Abstract

150 WORDS) Astroglial cells are emerging as key players in the development and homeostatic maintenance of neurons and neuronal networks. Astroglial cell functions are critical to neuronal migration and maturation, myelination, and synapse dynamics, however little is known about astroglial phenotypic changes over development. Furthermore, astroglial cells express steroid hormone receptors and show rapid responses to hormonal manipulations, however, despite important sex differences in telencephalic regions such as the cortex and hippocampus few studies have examined sex differences in astroglial cells in development and outside of the hypothalamus and amygdala. To phenotype cortical astroglial cells across postnatal development while considering potential sex differences, we used translating ribosome affinity purification together withRNAsequencing (TRAPseq) and immunohistochemistry to phenotype the entire astroglial translatome in males and females at key developmental time points: P1, P4, P7, P14, P35 and in adulthood. We found that although astroglia show few sex differences in adulthood, they show significant sex differences in developmental gene expression patterns between p7 and P35, that suggest sex differences in developmental functions. We also found two distinctive, non-overlapping, astroglial phenotypes between early (P1-P7) and late development (P14-Adult). Together these data clearly delineate and phenotype astroglia across development and identify sex differences in astroglial developmental programs that could have an important impact on the construction and maintenance of neuronal networks and related behavioural phenotypes.

Ion Channels and Electrophysiological Properties of Astrocytes: Implications for Emergent Stimulation Technologies

“…An increase in the neuronal expression of KCC2 early in development is believed to drive the shift of GABA from an excitatory to an inhibitory neurotransmitter (Moore et al, 2019 ). However, KCC2 is also expressed in astrocytes (Annunziato et al, 2013 ; Rurak et al, 2020 ), and this expression increases across development (Rurak et al, 2020 ). Perhaps the increase in KCC2 expression in astrocytes, and subsequent changes in intracellular K + and Cl + levels and reversal potentials, is what drives the changes in the electrophysiological properties such as RMP over development.…”

“…The robust expression of the K ir 4.1 subtype is believed to contribute to the high resting conductance of K + in astrocytes (Tang et al, 2009 ). However, expression of the K ir 4.1 subtype within astrocytes is variable; the channel is expressed in the spinal cord (Olsen et al, 2006 ), deep cerebellar nuclei, Müller glia of the retina as well as a subset of the hippocampus, but not in all astrocytes found within the hippocampus and white matter (Poopalasundaram et al, 2000 ; Higashi et al, 2001 ; Rurak et al, 2020 ). In a comprehensive analysis of K ir 4.1 subtype expression in glial cells, K ir 4.1 immunoreactivity was enriched in astrocytic processes wrapped around blood vessels (Hibino et al, 2004 ) and at synapses.…”

“…Voltage-dependent Na + channels consist of an α-subunit, of which there are nine isoforms (Na v 1.1–Na v 1.9) and a β-subunit of which there are only four isoforms (Pappalardo et al, 2016 ; Verkhratsky and Nedergaard, 2018 ). Astrocyte expression of these voltage-gated Na + channels has been noted in regions such as the spinal cord, cerebellum, optic nerve, cortex, and hippocampus (Sontheimer et al, 1991 ; Black et al, 1995 ; Kressin et al, 1995 ; Reese and Caldwell, 1999 ; Schaller and Caldwell, 2003 ; Ziemens et al, 2019 ; Rurak et al, 2020 ). Sodium signals have also been measured in astrocytes of the white matter (Moshrefi-Ravasdjani et al, 2017 ).…”

“…The (gene) expression of these Na v subtypes has been noted to change across development, at least in cortical astrocytes (Rurak et al, 2020 ). In this study, the authors combined translating ribosome affinity purification with RNA sequencing (TRAPseq) to measure gene expression changes specifically in cortical astrocytes.…”

“…In this study, the authors combined translating ribosome affinity purification with RNA sequencing (TRAPseq) to measure gene expression changes specifically in cortical astrocytes. Across development, there was significant differential expression of several genes that encode for voltage-gated Na + channels, including SCN1A (which encodes for the Na v 1.1 subtype), SCN3A (Na v 1.3), SCN8A (Na v 1.6), and SCN11A (Na v 1.9; Rurak et al, 2020 ). Though these differentially expressed genes were not validated using alternative methods (i.e., RT-qPCR), they do suggest that the physiological properties of astrocytes (such as Na + channels and signaling) are highly dynamic across development, and extrapolating data to other studies must be done with caution.…”