Extensive transcriptional and chromatin changes underlie astrocyte maturationin vivoand in culture

Abstract

Astrocytes have diverse functions in brain homeostasis. Many of these functions are acquired during late stages of differentiation when astrocytes become fully mature. The mechanisms underlying astrocyte maturation are not well understood. Here we identified extensive transcriptional changes that occur during astrocyte maturation and are accompanied by chromatin remodelling at enhancer elements. Investigating astrocyte maturation in a cell culture model revealed that in vitro-differentiated astrocytes lacked expression of many mature astrocyte-specific genes, including genes for the transcription factors Rorb, Dbx2, Lhx2 and Fezf2. Forced expression of these factors in vitro induced distinct sets of mature astrocytesspecific transcripts. Culturing astrocytes with FGF2 in a three-dimensional gel induced expression of Rorb, Dbx2 and Lhx2 and improved their maturity based on transcriptional and chromatin profiles. Therefore extrinsic signals orchestrate the expression of multiple intrinsic regulators, which in turn induce in a modular manner the transcriptional and chromatin changes underlying astrocyte maturation.

Epigenetic control of region‐specific transcriptional programs in mouse cerebellar and cortical astrocytes

“…The cooperative function of these transcription factors in adult astrocytes has yet to be investigated in detail on a molecular level. A recent study investigated transcriptional and chromatin changes of cortical astrocyte maturation in vivo and in vitro (Lattke, Goldstone, & Guillemot, 2020; bioRxiv preprint). Lattke and colleagues found Lhx2 and Fezf2, which are also identified as cortical factors in this study, to be involved in astrocyte maturation in the mouse cortex in vivo.…”

Time series scRNAseq analysis in mouse and human informs optimization of rapid astrocyte differentiation protocols

“…Much work over the past decade has implicated individual transcription factors 27 and signaling molecules in mouse astrocyte differentiation from mESCs, however no one has yet examined this process using scRNAseq. Moreover, a recent report suggested that current murine astrocyte differentiation protocols are unable to produce true, mature astrocytes 41 , in contrast to the thoroughly verified 37 human differentiation protocol we analyzed above. Other research groups have also revealed a similar lack of maturity in astrocytes differentiated without cues from neurons 24,38 .…”

“…We next compared our mouse differentiation data with a recent scRNAseq dataset of early astrocytes acutely purified from 3 day old mice using the cell surface marker ACSA-2 41 . We integrated our data from the last five timepoints (AD and FGF1/BMP4 exposure; identification of Atp1b2/ACSA-2 negative glial progenitors in the murine cerebellum 71 .…”

“…Even though we understand less about human glial development, there are protocols for human astrocyte diff erentiation that have been verifi ed at the scRNAseq level by comparing gene expression to acutely isolated human astrocytes 37 . Conversely, there are many mouse astrocyte diff erentiation protocols [38][39][40][41] , but these have not widely compared the diff erentiated cells to acutely purifi ed bona fi de primary cells via scRNAseq. This is an important gold standard for a diff erentiation protocol, as the ideal diff erentiated version of a cell type would be indistinguishable from the primary cell type at the transcriptomic, proteomic, and functional levels.…”

“…This is an important gold standard for a diff erentiation protocol, as the ideal diff erentiated version of a cell type would be indistinguishable from the primary cell type at the transcriptomic, proteomic, and functional levels. While the fi rst scRNAseq analyses of mouse glial development have begun to appear 41,42 , no one has yet produced such an analysis for the diff erentiation of astrocytes from mouse stem 1…”