Nuclear Factor I Isoforms Regulate Gene Expression During the Differentiation of Human Neural Progenitors to Astrocytes

Abstract

Even though astrocytes are critical for both normal brain functions and the development and progression of neuropathological states, including neuroinflammation associated with neurodegenerative diseases, the mechanisms controlling gene expression during astrocyte differentiation are poorly understood. Thus far, several signaling pathways were shown to regulate astrocyte differentiation, including JAK-STAT, BMP-2/Smads, and Notch. More recently, a family of Nuclear Factor-1 (NFI-A, -B, -C, and -X) was implicated in the regulation of vertebral neocortex development, with NFI-A and -B controlling the onset of gliogenesis. Here, we developed an in vitro model of differentiation of stem cells towards neural progenitors and subsequently astrocytes. The transition from stem cells to progenitors was accompanied by an expected change in the expression profile of markers, including Sox-2, Musashi-1, and Oct4. Subsequently, generated astrocytes were characterized by proper morphology, increased glutamate uptake, and marker gene expression. We used this in vitro differentiation model to study the expression and functions of NFIs. Interestingly, stem cells expressed only background levels of NFIs, while differentiation to neural progenitors activated the expression of NFI-A. More importantly, NFI-X expression was induced during the later stages of differentiation towards astrocytes. In addition, NFI-X and -C were required for the expression of GFAP and SPARCL1, which are the markers of astrocytes at the later stages of differentiation. We conclude that an expression program of NFIs is executed during the differentiation of astrocytes, with NFI-X and -C controlling the expression of astrocytic markers at late stages of differentiation.

Astrocytes and disease: a neurodevelopmental perspective

“…However, analysis at later embryonic stages revealed a drastic decrease in the expression of GFAP in the embryonic brain and spinal cord, indicating that both these genes are necessary for astrocyte differentiation in vivo (das Neves et al 1999;Steele-Perkins et al 2005). These findings are supported by several in vitro studies indicating that NFI genes directly regulate the expression of GFAP during astrocyte differentiation in various cell systems, including human and mouse neural progenitors (Cebolla and Vallejo 2006;Wilczynska et al 2009). In addition to direct regulation of GFAP, NFIA may potentiate STAT3 activation of GFAP in vitro by epigenetic mechanisms (Namihira et al 2009).…”

A Complex of Nuclear Factor I-X3 and STAT3 Regulates Astrocyte and Glioma Migration through the Secreted Glycoprotein YKL-40

“…Consequently, Nfia, Nfib, and Nfix knock-out mice show severe brain anatomical defects, including agenesis of corpus callosum (9, 10), whereas NPs from Nfix knock-out mice show defects in proliferation and migration (9, 10). NFI-A and -B control gliogenesis in chick embryonic spinal cord (7), whereas NFI-X and -C regulate the expression of late astrocyte markers during the differentiation of human NPs in vitro (7,8). Expression of NFI-A is induced by Notch signaling in NP and leads to the demethylation of astrocyte-specific genes (11), as well as down-regulation of Notch signaling via repression of Notch effector Hes1 (12).…”

“…Generation and differentiation of astrocytes from neural progenitors is controlled by activation of the JAK-STAT3, BMP-SMAD, and Notch-HES pathways in vivo (3, 4) and promoted by cytokines of the IL-6 family that activate STAT3 in vitro (5, 6). In addition to these pathways, evolutionarily conserved NFI 3 transcription factors, consisting of NFI-A, -B, -C, and -X, regulate astrocyte differentiation (7,8). NFIs are expressed in overlapping patterns during embryogenesis, with high expression levels of NFI-A, -B, and -X found in the developing neocortex (9, 10).…”

“…transcription factors, consisting of NFI-A, -B, -C, and -X, regulate astrocyte differentiation (7,8). NFIs are expressed in overlapping patterns during embryogenesis, with high expression levels of NFI-A, -B, and -X found in the developing neocortex (9,10).…”

Developmental control of cortico-cerebral astrogenesis

“…No gliogenic anomaly was conversely found upon manipulation of Lhx2 activity in neocortical precursors (Subramanian et al, 2011). Finally, in addition to promoting primary opening of Gfap chromatin, Nf1a might further sustain transcription of this chromatin at more advanced steps of astroglial differentiation, synergizing with its later activated paralogs, Nf1b, Nf1c and Nf1x (Wilczynska et al, 2009).…”