Zac1 Regulates Astroglial Differentiation of Neural Stem Cells Through Socs3

Abstract

Cell-fate decisions and differentiation of embryonic and adult neural stem cells (NSC) are tightly controlled by lineage-restricted and temporal factors that interact with cell-intrinsic programs and extracellular signals through multiple regulatory loops. Imprinted genes are important players in neurodevelopment and mental health although their molecular and cellular functions remain poorly understood. Here, we show that the paternally expressed transcriptional regulator Zac1 (zinc finger protein regulating apoptosis and cell cycle arrest) is transiently induced during astroglial and neuronal differentiation of embryonic and adult NSC lines. Thereby, Zac1 transactivates Socs3 (suppressor of cytokine signaling 3), a potent inhibitor of prodifferentiative Jak/Stat3 signaling, in a lineage-specific manner to prevent precocious astroglial differentiation. In vivo, Zac1 and Socs3 colocalize in the neocortical ventricular zone during incipient astrogliogenesis. Zac1 overexpression in primary NSCs delays astroglial differentiation whereas knockdown of Zac1 or Socs3 facilitates formation of astroglial cells. This negative feedback loop is unrelated to Zac1 0 s cell cycle arrest function and specific to the Jak/Stat3 pathway. Hence, reinstating Jak/Stat3 signaling in the presence of increased Zac1 expression allows for timely astroglial differentiation. Overall, we suggest that the imprinted gene Zac1 curtails astroglial differentiation of NSCs in the developing and adult brain.

Zac1 Regulates Cell Cycle Arrest in Neuronal Progenitors via Tcf4

“…Direct Zac1 target genes identified so far include the G-protein-coupled receptor PacI (pituitary adenylate-activating receptor I) gene (18)(19)(20), the nuclear receptor gene Ppar␥1 (peroxisome proliferatoractivated receptor gene) (21), the cyclin-dependent kinase inhibitor gene p21 Waf1/Cip1 (22), and the exchange factor gene Rasgrf1 (RAS protein-specific guanine nucleotide-releasing factor 1 gene) (23), all of which share a role in the regulation of apoptosis, cell cycle arrest, and differentiation across different tissues and stages of development. Moreover, we recently found that Zac1 expression prevents precocious astroglial differentiation by restraining Jak/Stat3 signaling in embryonic and adult neural stem cells (NSCs) through transcriptional induction of Socs3 (24). Here, we further show that Tcf4 is a lineage-specific target gene of Zac1 in the control of neuronal progenitor cell cycle arrest function, consistent with a role of Zac1 in both lineage decisions.…”

“…In addition, cells were differentiated by treatment with all-trans retinoic acid (RA) (0.1 M) or by embryoid body (EB) formation as reported previously (26). The mouse embryonic NS-5 and adult O4ANS NSC lines were grown as reported previously (24). Primary cells from whole fetal brain (embryonic day 15 [E15]) of CD1 mice were dissected as described previously (24) and grown as a suspension in DMEM-F-12 and neurobasal medium (1:1) supplemented with N2 (1%, vol/vol), B27 (2%, vol/vol) (all from Life Technologies GmbH), epidermal growth factor (EGF), and fibroblast growth factor (FGF) (both at 10 ng/ml; Pep-roTech, Hamburg, Germany).…”

“…The mouse embryonic NS-5 and adult O4ANS NSC lines were grown as reported previously (24). Primary cells from whole fetal brain (embryonic day 15 [E15]) of CD1 mice were dissected as described previously (24) and grown as a suspension in DMEM-F-12 and neurobasal medium (1:1) supplemented with N2 (1%, vol/vol), B27 (2%, vol/vol) (all from Life Technologies GmbH), epidermal growth factor (EGF), and fibroblast growth factor (FGF) (both at 10 ng/ml; Pep-roTech, Hamburg, Germany). Neurospheres were dissociated with Accutase (Millipore, Schwalbach, Germany) and grown as monolayers on poly-D-lysine hydrobromide (Sigma, Munich, Germany)-coated plates in the presence of EGF and FGF.…”

“…Transient and stable transfections were performed by using Turbofect transfection reagent (Fermentas, St. Leon-Roth, Germany) according to the manufacturer's instructions, using 1 ϫ 10 5 to 5 ϫ 10 5 cells/cm 2 as described previously (24). To knock down Zac1, p57…”

First principles of Hamiltonian medicine

“…Such effects are expected because during development, power over phenotypes is commonly (i) some function of time, because events earlier in ontogeny have larger, more-cascading effects, and (ii) some function of control over rates and patterns of cell and tissue proliferation, because this is how organisms grow and differentiate. This prediction is well supported by recent studies showing that in a wide range of human tissues, imprinted genes orchestrate stem cell replication versus inhibition [96][97][98], and by the observation that imprinted genes exert especially pervasive effects on placental development, at the start of fetal growth and development [99,100]. Imprintedgene conflicts will therefore be especially important in mediating causes of variation in physical health, because so many human health outcomes are highly dependent on early-life events and phenotypes such as placental function and birth weight [101], and on the roles of stem cells in tissue renewal and repair.…”