Extensive transcriptional and chromatin changes underlie astrocyte maturation in vivo and in culture

Michael Lattke,Nicolás Marichal,Stefan Boeing,James K Ellis,Benedikt Berninger,James I Macrae,Jerónimo Jurado-Arjona,Robert Goldstone,Francois Guillemot

doi:10.1038/s41467-021-24624-5

Abstract

Astrocytes have essential functions in brain homeostasis that are established late in differentiation, but the mechanisms underlying the functional maturation of astrocytes are not well understood. Here we identify extensive transcriptional changes that occur during murine astrocyte maturation in vivo that are accompanied by chromatin remodelling at enhancer elements. Investigating astrocyte maturation in a cell culture model revealed that in vitro-differentiated astrocytes lack 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 induces distinct sets of mature astrocyte-specific transcripts. Culturing astrocytes in a three-dimensional matrix containing FGF2 induces expression of Rorb, Dbx2 and Lhx2 and improves astrocyte 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.

Highlights

Astrocytes have essential functions in brain homeostasis that are established late in differentiation, but the mechanisms underlying the functional maturation of astrocytes are not well understood
To gain a better understanding of the molecular mechanisms underlying astrocyte maturation, we examined astrocytes isolated from mice at an early postnatal stage, when astrocytes have been specified but remain immature and partially proliferating, and at a young adult stage (~3 months), when astrocytes have reached full maturity (Fig. 1a)
We have analysed in detail the transcriptional and chromatin changes that occur during maturation of astrocytes in the mouse forebrain

Summary

Introduction

Astrocytes have essential functions in brain homeostasis that are established late in differentiation, but the mechanisms underlying the functional maturation of astrocytes are not well understood. Investigating astrocyte maturation in a cell culture model revealed that in vitrodifferentiated astrocytes lack expression of many mature astrocyte-specific genes, including genes for the transcription factors Rorb, Dbx[2], Lhx[2] and Fezf[2]. The functions of astrocytes change profoundly during their maturation, the regulatory mechanisms underlying these changes have only begun to be examined This analysis has been performed mostly in in vitro models, including cultures of acutely isolated postnatal astrocytes, cultures of NSCs differentiated with agonists of the BMP or JAK-STAT signalling pathways[9,10,11,12], and pluripotent stem cell-derived three dimensional neural cultures or spheroids[13]. In vitro-differentiated astrocytes are thought to remain immature[15,16,17], and it is, unclear whether the mechanisms identified so far are sufficient to account for the complete maturation of astrocytes in vivo

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Results

Conclusion