A Novel SALL4/OCT4 Transcriptional Feedback Network for Pluripotency of Embryonic Stem Cells

Abstract

BackgroundSALL4 is a member of the SALL gene family that encodes a group of putative developmental transcription factors. Murine Sall4 plays a critical role in maintaining embryonic stem cell (ES cell) pluripotency and self-renewal. We have shown that Sall4 activates Oct4 and is a master regulator in murine ES cells. Other SALL gene members, especially Sall1 and Sall3 are expressed in both murine and human ES cells, and deletions of these two genes in mice lead to perinatal death due to developmental defects. To date, little is known about the molecular mechanisms controlling the regulation of expressions of SALL4 or other SALL gene family members.Methodology/Principal FindingsThis report describes a novel SALL4/OCT4 regulator feedback loop in ES cells in balancing the proper expression dosage of SALL4 and OCT4 for the maintenance of ESC stem cell properties. While we have observed that a positive feedback relationship is present between SALL4 and OCT4, the strong self-repression of SALL4 seems to be the “break” for this loop. In addition, we have shown that SALL4 can repress the promoters of other SALL family members, such as SALL1 and SALL3, which competes with the activation of these two genes by OCT4.Conclusions/SignificanceOur findings, when taken together, indicate that SALL4 is a master regulator that controls its own expression and the expression of OCT4. SALL4 and OCT4 work antagonistically to balance the expressions of other SALL gene family members. This novel SALL4/OCT4 transcription regulation feedback loop should provide more insight into the mechanism of governing the “stemness” of ES cells.

Defeating EpCAM+ liver cancer stem cells by targeting chromatin remodeling enzyme CHD4 in human hepatocellular carcinoma

“…Using gene expression profiling approaches, we recently identified the activation of transcription factor Sal-like protein 4transcription factor which plays a fundamental role in the maintenance of embryonic stem cells, possibly through interaction with octamer-binding transcription factor 4, sex determining region Y-box 2, and Nanog [19][20][21][22][23][24]. It has been reported by three independent groups that SALL4 is a biomarker of HCCs with stem-like gene expression signatures and a poor prognosis [18,25,26].…”

Stem Cell Gene SALL4 Suppresses Transcription through Recruitment of DNA Methyltransferases

“…Plasmid Constructions-The following plasmids have been described previously: pcDNA3-SALL4A-HA, pcDNA3-SALL4B-HA, pSALL1-Luc reporter, pSALL3-Luc reporter, pSALL4-Luc reporter, and pOCT4-Luc reporter (15). The primers used in generating SALL4 deletion mutants are described in supplemental Table S1.…”

“…Transfection of plasmids into cultured cells was performed using Lipofectamine 2000 (Invitrogen) according to the manufacturer's recommendations. Luciferase assays were performed as described previously (15). Epigenetic drugs (valproic acid and 5-azacytidine) were purchased form Sigma.…”

“…We recently reported that in embryonic stem cells, SALL4 and OCT4 form a regulatory feedback loop (15). Importantly, SALL4 possesses a strong self-repressive effect, which seems to set a tight regulation for the proper expression of both genes (15). In the beginning of this study, we asked whether inhibition of the histone deacetylase can completely block the self-repression effect of SALL4.…”

“…The SALL4-NuRD complex possesses histone deacetylase (HDAC) 2 activity, which may participate in the repressing effects of SALL4 (14). We recently reported that in embryonic stem cells, SALL4 and OCT4 form a regulatory feedback loop (15). Importantly, SALL4 possesses a strong self-repressive effect, which seems to set a tight regulation for the proper expression of both genes (15).…”