SUMO-dependent transcriptional repression by Sox2 inhibits the proliferation of neural stem cells.

Sox2 is known for its roles in maintaining the stem cell state of embryonic stem cells and neural stem cells. In particular, it has been shown to slow the proliferation of these cell types. It is also known for its effects as an activating transcription factor.

3D spheroid models of paediatric SHH medulloblastoma mimic tumour biology, drug response and metastatic dissemination.

Studying medulloblastoma, the most common malignant paediatric brain tumour, requires simple yet realistic in vitro models. In this study, we optimised a robust, reliable, three-dimensional (3D) culture method for medulloblastoma able to recapitulate the spatial conformation, cell-cell and cell-matrix interactions that exist in vivo and in patient tumours. We show that, when grown under the same stem cell enriching conditions, SHH subgroup medulloblastoma cell lines established tight, highly reproducible 3D spheroids that could be maintained for weeks in culture and formed pathophysiological oxygen gradients.

Genome-wide methylation analysis identifies genes silenced in non-seminoma cell lines.

Silencing of genes by DNA methylation is a common phenomenon in many types of cancer. However, the genome-wide effect of DNA methylation on gene expression has been analysed in relatively few cancers. Germ cell tumours (GCTs) are a complex group of malignancies.

Sox2 acts as a transcriptional repressor in neural stem cells.

Background: The transcription factor, Sox2, is central to the behaviour of neural stem cells. It is also one of the key embryonic stem cell factors that, when overexpressed can convert somatic cells into induced pluripotent cells. Although generally studied as a transcriptional activator, recent evidence suggests that it might also repress gene expression.

Formation of the embryonic organizer is restricted by the competitive influences of Fgf signaling and the SoxB1 transcription factors.

The organizer is one of the earliest structures to be established during vertebrate development and is crucial to subsequent patterning of the embryo. We have previously shown that the SoxB1 transcription factor, Sox3, plays a central role as a transcriptional repressor of zebrafish organizer gene expression. Recent data suggest that Fgf signaling has a positive influence on organizer formation, but its role remains to be fully elucidated.

Akt1 mediates neuronal differentiation in zebrafish via a reciprocal interaction with notch signaling.

Akt1 is well known for its role in regulating cell proliferation, differentiation, and apoptosis and is implicated in tumors and several neurological disorders. However, the role of Akt1 in neural development has not been well defined. We have isolated zebrafish akt1 and shown that this gene is primarily transcribed in the developing nervous system, and its spatiotemporal expression pattern suggests a role in neural differentiation.

Zebrafish rgs4 is essential for motility and axonogenesis mediated by Akt signaling.

The schizophrenia susceptibility gene, Rgs4, is one of the most intensively studied regulators of G-protein signaling members, well known to be fundamental in regulating neurotransmission. However, little is known about its role in the developing nervous system. We have isolated zebrafish rgs4 and shown that it is transcribed in the developing nervous system.

Stem cell research points the way to the cell of origin for intracranial germ cell tumours.

Germ cell tumours found in the brain (intracranial GCTs) are a very unusual class of tumour for two reasons. First, they include a very diverse range of histological subtypes classified together due to their proposed common cell of origin. Second, this proposed cell of origin, the germ cell progenitor, would not normally be found in the tissue where these tumours arise.

The developmental dismantling of pluripotency is reversed by ectopic Oct4 expression.

The transcription factors Nanog and Oct4 regulate pluripotency in the pre-implantation epiblast and in derivative embryonic stem cells. During post-implantation development, the precise timing and mechanism of the loss of pluripotency is unknown. Here, we show that in the mouse, pluripotency is extinguished at the onset of somitogenesis, coincident with reduced expression and chromatin accessibility of Oct4 and Nanog regulatory regions.

Zebrafish Her8a is activated by Su(H)-dependent Notch signaling and is essential for the inhibition of neurogenesis.

Understanding how diversity of neural cells is generated is one of the main tasks of developmental biology. The Hairy/E(spl) family members are potential targets of Notch signaling, which has been shown to be fundamental to neural cell maintenance, cell fate decisions, and compartment boundary formation. However, their response to Notch signaling and their roles in neurogenesis are still not fully understood.

Dynamic methylation and expression of Oct4 in early neural stem cells.

Neural stem cells are a multipotent population of tissue-specific stem cells with a broad but limited differentiation potential. However, recent studies have shown that over-expression of the pluripotency gene, Oct4, alone is sufficient to initiate a process by which these can form 'induced pluripotent stem cells' (iPS cells) with the same broad potential as embryonic stem cells. This led us to examine the expression of Oct4 in endogenous neural stem cells, as data regarding its expression in neural stem cells in vivo are contradictory and incomplete.

The surface ectoderm of the chick embryo exhibits dynamic variation in its response to neurogenic signals.

The epibranchial placodes are specialized areas of surface ectoderm that make a vital contribution to the peripheral nervous system, producing sensory neurons of the cranial ganglia. They have long been characterized as a series of patches of thickened ectoderm in the vicinity of each pharyngeal cleft. We have previously demonstrated that Sox3 is not only expressed in these structures but also marks a larger, earlier domain.

Sox3 regulates both neural fate and differentiation in the zebrafish ectoderm.

Little is known of the first transcriptional events that regulate neural fate in response to extracellular signals such as Bmps and Fgfs. Sox3 is one of the earliest transcription factors to be expressed in the developing CNS and has been shown to be regulated by these signalling pathways. We have used both gain- and loss-of-function experiments in zebrafish to elucidate the role of Sox3 in determining neural fate.

Foregut endoderm is specified early in avian development through signal(s) emanating from Hensen's node or its derivatives.

In this study, the initial specification of foregut endoderm in the chick embryo was analyzed. A fate map constructed for the area pellucida endoderm at definitive streak-stage showed centrally-located presumptive cells of foregut-derived organs around Hensen's node. Intracoelomic cultivation of the area pellucida endoderm at this stage combined with somatic mesoderm resulted in the differentiation predominantly into intestinal epithelium, suggesting that this endoderm may not yet be regionally specified.

Cyclopamine inhibition of the sonic hedgehog pathway in the stomach requires concomitant acid inhibition.

The Shh pathway has been implicated in gastric carcinogenesis, and inhibition of this pathway has been shown to inhibit tumour growth in gastric cell lines. Assessing the in vivo efficacy of Shh pathway antagonists in blocking Shh signaling in the stomach is important for clinical trial design, but has not been previously investigated. We investigated the in vivo efficacy of a Shh antagonist, cyclopamine, in correlation to the secondary effects induced by this treatment on gastrin levels and acid secretion.

Evolutionary conservation of a coding function for D4Z4, the tandem DNA repeat mutated in facioscapulohumeral muscular dystrophy.

Facioscapulohumeral muscular dystrophy (FSHD) is caused by deletions within the polymorphic DNA tandem array D4Z4. Each D4Z4 repeat unit has an open reading frame (ORF), termed "DUX4," containing two homeobox sequences. Because there has been no evidence of a transcript from the array, these deletions are thought to cause FSHD by a position effect on other genes.

Epibranchial and otic placodes are induced by a common Fgf signal, but their subsequent development is independent.

The epibranchial placodes are cranial, ectodermal thickenings that give rise to sensory neurons of the peripheral nervous system. Despite their importance in the developing animal, the signals responsible for their induction remain unknown. Using the placodal marker, sox3, we have shown that the same Fgf signaling required for otic vesicle development is required for the development of the epibranchial placodes.

A change in response to Bmp signalling precedes ectodermal fate choice.

Bone morphogenetic protein (Bmp) signalling plays a central role in the decision of ectoderm to adopt either neural or non-neural fates. The effects of this signalling are seen at mid-gastrulation in the activation of genes such as the Gata factors and the repression of genes such as the SoxB1 transcription factors in the non-neural regions. Using zebrafish embryos, we show that this Bmp signalling does not repress the expression of these same neural markers just 2-3 hours earlier.

Stem cell marker expression in the Bergmann glia population of the adult mouse brain.

Recent evidence suggests that the postnatal cerebellum contains cells with characteristics of neural stem cells, which had so far only been identified in the subventricular zone of the lateral ventricles and the subdentate gyrus of the hippocampus. In order to investigate the identity of these cells in the adult cerebellum, we have analyzed the expression of Sox1, a transcription factor from the SoxB1 subgroup and widely used marker of neural stem cells. In situ hybridization and the use of a transgenic mouse model show that, in the adult cerebellum, Sox 1 is only expressed in the Bergmann glia, a population of radial glia present in the Purkinje cell layer.

Strategies to investigate gene expression and function in granule cells.

Studying gene expression in granule cells is a major route to understanding the factors required for many key cellular processes such as specification, proliferation, migration, differentiation, apoptosis, tumour formation and neurodegeneration. A greater understanding of these processes will not only provide insight into cerebellum development, but also diseases of the cerebellum. Granule cells can be readily grown in culture and both viral and non-viral strategies have been optimised to allow gene transfer and expression in cultured cells.

CIC, a gene involved in cerebellar development and ErbB signaling, is significantly expressed in medulloblastomas.

In children, the majority of brain tumors arise in the cerebellum. Medulloblastomas, the most common of these, are believed to originate from the granule cell lineage. We have recently identified a mammalian gene, capicua (Cic), the ortholog of a Drosophila gene implicated in c-erbB (Egfr) signaling, which is predominantly expressed during mouse granule cell development.

Childhood solid tumours: a developmental disorder.

Several lines of evidence demonstrate that the biology, genetics and environment of childhood solid tumours (CSTs) sets them apart from adult solid tumours. The nature of the progenitor cells from which these tumours arise, and their immature tissue environment, allows CSTs to develop with fewer defects in cell regulatory processes than adult cancers. These differences could explain why CSTs are more susceptible to therapeutic intervention than adult tumours.