Transcription factor Sox10 orchestrates activity of a neural crest-specific enhancer in the vicinity of its gene

The Sox10 transcription factor is a central regulator of vertebrate neural crest and nervous system development. Its expression is likely controlled by multiple enhancer elements, among them U3 (alternatively known as MCS4). Here we analyze U3 activity to obtain deeper insights into Sox10 function and expression in the neural crest and its derivatives. U3 activity strongly depends on the presence of Sox10 that regulates its own expression as commonly observed for important developmental regulators. Sox10 bound directly as monomer to at least three sites in U3, whereas a fourth site preferred dimers. Deletion of these sites efficiently reduced U3 activity in transfected cells and transgenic mice. In stimulating the U3 enhancer, Sox10 synergized with many other transcription factors present in neural crest and developing peripheral nervous system including Pax3, FoxD3, AP2α, Krox20 and Sox2. In case of FoxD3, synergism involved Sox10-dependent recruitment to the U3 enhancer, while Sox10 and AP2α each had to bind to the regulatory region. Our study points to the importance of autoregulatory activity and synergistic interactions for maintenance of Sox10 expression and functional activity of Sox10 in the neural crest regulatory network

Genomics and proteomics in stem cell research: the road ahead

Stem cell research has been widely studied over the last few years and has attracted increasing attention from researchers in all fields of medicine due to its potential to treat many previously incurable diseases by replacing damaged cells or tissues. As illustrated by hematopoietic stem research, understanding stem cell differentiation at molecular levels is essential for both basic research and for clinical applications of stem cells. Although multiple integrative analyses, such as genomics, epigenomics, transcriptomics and proteomics, are required to understand stem cell biology, proteomics has a unique position in stem cell research. For example, several major breakthroughs in HSC research were due to the identification of proteins such as colony-stimulating factors (CSFs) and cell-surface CD molecules. In 2007, the Human Proteome Organization (HUPO) and the International Society for Stem Cell Research (ISSCR) launched the joint Proteome Biology of Stem Cells Initiative. A systematic proteomics approach to understanding stem cell differentiation will shed new light on stem cell biology and accelerate clinical applications of stem cells

Sox4 mediates Tbx3 transcriptional regulation of the gap junction protein Cx43

Tbx3, a T-box transcription factor, regulates key steps in development of the heart and other organ systems. Here, we identify Sox4 as an interacting partner of Tbx3. Pull-down and nuclear retention assays verify this interaction and in situ hybridization reveals Tbx3 and Sox4 to co-localize extensively in the embryo including the atrioventricular and outflow tract cushion mesenchyme and a small area of interventricular myocardium. Tbx3, SOX4, and SOX2 ChIP data, identify a region in intron 1 of Gja1 bound by all tree proteins and subsequent ChIP experiments verify that this sequence is bound, in vivo, in the developing heart. In a luciferase reporter assay, this element displays a synergistic antagonistic response to co-transfection of Tbx3 and Sox4 and in vivo, in zebrafish, drives expression of a reporter in the heart, confirming its function as a cardiac enhancer. Mechanistically, we postulate that Sox4 is a mediator of Tbx3 transcriptional activity

The molecular machinery of myelin gene transcription in Schwann cells

During late fetal life, Schwann cells in the peripheral nerves, singled out by the larger axons will transit through a promyelinating stage before exiting the cell cycle and initiating myelin formation. A network of extra- and intracellular signaling pathways, regulating a transcriptional program of cell differentiation, governs this progression of cellular changes, culminating in a highly differentiated cell. In this review we focus on the roles of a number of transcription factors not only in myelination, during normal development, but also in demyelination, following nerve trauma. These factors include specification factors involved in early development of Schwann cells from neural crest (Sox10) as well as factors specifically required for transitions into the promyelinating and myelinating stages (Oct6/Scip and Krox20/Egr2). From this description we can glean the first, still very incomplete, contours of a gene regulatory network that governs myelination and demyelination during development and regeneration

Regulation of XFGF8 gene expression through SRY (sex-determining region Y)-box 2 in developing Xenopus embryos

Fibroblast growth factors (FGFs) function as mitogens and morphogens during vertebrate development. In the present study, to characterise the regulatory mechanism of FGF8 gene expression in developing Xenopus embryos the upstream region of the Xenopus FGF8 (XFGF8) gene was isolated. The upstream region of the XFGF8 gene contains two putative binding sites for the SRY (sex-determining region Y)-box 2 (SOX2) transcription factor. A reporter assay with serially deleted constructs revealed that the putative SOX2-binding motif may be a critical cis-element for XFGF8 gene activation in developing Xenopus embryos. Furthermore, Xenopus SOX2 (XSOX2) physically interacted with the SOX2-binding motif within the upstream region of the XFGF8 gene in vitro and in vivo. Depletion of endogenous XSOX2 resulted in loss of XFGF8 gene expression in midbrain-hindbrain junction, auditory placode, lens placode and forebrain in developing Xenopus embryos. Collectively, our results suggest that XSOX2 directly upregulates XFGF8 gene expression in the early embryonic development of Xenopus

Sox10 directs neural stem cells toward the oligodendrocyte lineage by decreasing Suppressor of Fused expression

Oligodendrocyte precursor cells (OPCs) are lineage-restricted progenitors generally limited in vivo to producing oligodendrocytes. Mechanisms controlling genesis of OPCs are of interest because of their importance in myelin development and their potential for regenerative therapies in multiple sclerosis and dysmyelinating syndromes. We show here that the SoxE transcription factors (comprising Sox8, 9, and 10) induce multipotent neural precursor cells (NPCs) from the early postnatal subventricular zone (SVZ) to become OPCs in an autonomous manner. We performed a chromatin immunoprecipitation-based bioinformatic screen and identified Suppressor of Fused (Sufu) as a direct target of repression by Sox10. In vitro, overexpression of Sufu blocked OPC production, whereas RNAi-mediated inhibition augmented OPC production. Furthermore, mice heterozygous for Sufu have increased numbers of OPCs in the telencephalon during development. We conclude that Sox10 acts to restrict the potential of NPCs toward the oligodendrocyte lineage in part by regulating the expression of Sufu

Phosphorylation Regulates OLIG2 Cofactor Choice and the Motor Neuron-Oligodendrocyte Fate Switch

A fundamental feature of central nervous system development is that neurons are generated before glia. In the embryonic spinal cord, for example, a group of neuroepithelial stem cells (NSCs) generates motor neurons (MNs), before switching abruptly to oligodendrocyte precursors (OLPs). We asked how transcription factor OLIG2 participates in this MN-OLP fate switch. We found that Serine 147 in the helix-loop-helix domain of OLIG2 was phosphorylated during MN production and dephosphorylated at the onset of OLP genesis. Mutating Serine 147 to Alanine (S147A) abolished MN production without preventing OLP production in transgenic mice, chicks, or cultured P19 cells. We conclude that S147 phosphorylation, possibly by protein kinase A, is required for MN but not OLP genesis and propose that dephosphorylation triggers the MN-OLP switch. Wild-type OLIG2 forms stable homodimers, whereas mutant (unphosphorylated) OLIG2S147A prefers to form heterodimers with Neurogenin 2 or other bHLH partners, suggesting a molecular basis for the switch