PAX6 does not regulate Nfia and Nfib expression during neocortical development

The Nuclear factor I (NFI) family of transcription factors regulates proliferation and differentiation throughout the developing central nervous system. In the developing telencephalon of humans and mice, reduced Nfi expression is associated with agenesis of the corpus callosum and other neurodevelopmental defects. Currently, little is known about how Nfi expression is regulated during early telencephalic development. PAX6, a transcription factor important for telencephalic development, has been proposed as an upstream regulator of Nfi expression in the neocortex. Here we demonstrate that, in the developing neocortex of mice, NFIA and NFIB are endogenously expressed in gradients with high caudo-medial to low rostro-lateral expression and are most highly expressed in the cortical plate. We found that this expression pattern deviates from that of PAX6, suggesting that PAX6 does not drive Nfi expression. This is supported by in vitro reporter assays showing that PAX6 overexpression does not regulate Nfi promoter activity. Similarly, we also found that in the Pax6 Small Eye mutant, no changes in Nfi mRNA or protein expression are observed in the neocortical ventricular zone where PAX6 and the NFIs are expressed. Together these data demonstrate that in mice, PAX6 is not a transcriptional activator of Nfi expression during neocortical development

The convergent roles of the nuclear factor I transcription factors in development and cancer

The nuclear factor I (NFI) transcription factors play important roles during normal development and have been associated with developmental abnormalities in humans. All four family members, NFIA, NFIB, NFIC and NFIX, have a homologous DNA binding domain and function by regulating cell proliferation and differentiation via the transcriptional control of their target genes. More recently, NFI genes have also been implicated in cancer based on genomic analyses and studies of animal models in a variety of tumours across multiple organ systems. However, the association between their functions in development and in cancer is not well described. In this review, we summarise the evidence suggesting a converging role for the NFI genes in development and cancer. Our review includes all cancer types in which the NFI genes are implicated, focusing predominantly on studies demonstrating their oncogenic or tumour suppressive potential. We conclude by presenting the challenges impeding our understanding of NFI function in cancer biology, and demonstrate how a developmental perspective may contribute towards overcoming such hurdles. (C) 2017 Elsevier B.V. All rights reserved

Joint Binding of OTX2 and MYC in Promotor Regions Is Associated with High Gene Expression in Medulloblastoma

Both OTX2 and MYC are important oncogenes in medulloblastoma, the most common malignant brain tumor in childhood. Much is known about MYC binding to promoter regions, but OTX2 binding is hardly investigated. We used ChIP-on-chip data to analyze the binding patterns of both transcription factors in D425 medulloblastoma cells. When combining the data for all promoter regions in the genome, OTX2 binding showed a remarkable bi-modal distribution pattern with peaks around −250 bp upstream and +650 bp downstream of the transcription start sites (TSSs). Indeed, 40.2% of all OTX2-bound TSSs had more than one significant OTX2-binding peak. This OTX2-binding pattern was very different from the TSS-centered single peak binding pattern observed for MYC and other known transcription factors. However, in individual promoter regions, OTX2 and MYC have a strong tendency to bind in proximity of each other. OTX2-binding sequences are depleted near TSSs in the genome, providing an explanation for the observed bi-modal distribution of OTX2 binding. This contrasts to the enrichment of E-box sequences at TSSs. Both OTX2 and MYC binding independently correlated with higher gene expression. Interestingly, genes of promoter regions with multiple OTX2 binding as well as MYC binding showed the highest expression levels in D425 cells and in primary medulloblastomas. Genes within this class of promoter regions were enriched for medulloblastoma and stem cell specific genes. Our data suggest an important functional interaction between OTX2 and MYC in regulating gene expression in medulloblastoma

Integrated Genomics Identifies Five Medulloblastoma Subtypes with Distinct Genetic Profiles, Pathway Signatures and Clinicopathological Features

BACKGROUND: Medulloblastoma is the most common malignant brain tumor in children. Despite recent improvements in cure rates, prediction of disease outcome remains a major challenge and survivors suffer from serious therapy-related side-effects. Recent data showed that patients with WNT-activated tumors have a favorable prognosis, suggesting that these patients could be treated less intensively, thereby reducing the side-effects. This illustrates the potential benefits of a robust classification of medulloblastoma patients and a detailed knowledge of associated biological mechanisms. METHODS AND FINDINGS: To get a better insight into the molecular biology of medulloblastoma we established mRNA expression profiles of 62 medulloblastomas and analyzed 52 of them also by comparative genomic hybridization (CGH) arrays. Five molecular subtypes were identified, characterized by WNT signaling (A; 9 cases), SHH signaling (B; 15 cases), expression of neuronal differentiation genes (C and D; 16 and 11 cases, respectively) or photoreceptor genes (D and E; both 11 cases). Mutations in beta-catenin were identified in all 9 type A tumors, but not in any other tumor. PTCH1 mutations were exclusively identified in type B tumors. CGH analysis identified several fully or partly subtype-specific chromosomal aberrations. Monosomy of chromosome 6 occurred only in type A tumors, loss of 9q mostly occurred in type B tumors, whereas chromosome 17 aberrations, most common in medulloblastoma, were strongly associated with type C or D tumors. Loss of the inactivated X-chromosome was highly specific for female cases of type C, D and E tumors. Gene expression levels faithfully reflected the chromosomal copy number changes. Clinicopathological features significantly different between the 5 subtypes included metastatic disease and age at diagnosis and histology. Metastatic disease at diagnosis was significantly associated with subtypes C and D and most strongly with subtype E. Patients below 3 yrs of age had type B, D, or E tumors. Type B included most desmoplastic cases. We validated and confirmed the molecular subtypes and their associated clinicopathological features with expression data from a second independent series of 46 medulloblastomas. CONCLUSIONS: The new medulloblastoma classification presented in this study will greatly enhance the understanding of this heterogeneous disease. It will enable a better selection and evaluation of patients in clinical trials, and it will support the development of new molecular targeted therapies. Ultimately, our results may lead to more individualized therapies with improved cure rates and a better quality of life

Mutations in DCC cause isolated agenesis of the corpus callosum with incomplete penetrance

Brain malformations involving the corpus callosum are common in children with developmental disabilities. We identified DCC mutations in four families and five sporadic individuals with isolated agenesis of the corpus callosum (ACC) without intellectual disability. DCC mutations result in variable dominant phenotypes with decreased penetrance, including mirror movements and ACC associated with a favorable developmental prognosis. Possible phenotypic modifiers include the type and location of mutation and the sex of the individual

The role of OTX2 in medulloblastoma

Het onderdrukken van het gen OTX2 lijkt een potentiële therapie voor medulloblastomen, een kwaadaardige hersentumor. Jens Bunt stelt dat OTX2 door binding aan het DNA de expressie van genen die nodig zijn voor celdeling aanzet, terwijl het indirect de differentiatie van cellen remt. Uit proeven met tumorcellen waarin OTX2 aan of uit gezet kan worden, blijkt dat OTX2 noodzakelijk is voor de vermeerdering van de medulloblastoomcellen. Het medulloblastoom is een kwaadaardige tumor van de kleine hersenen, meestal bij kinderen. Het gen OTX2, dat normaal alleen aanstaat tijdens de ontwikkeling, komt hoog tot expressie in de meerderheid van de tumoren

MicroRNA-153 regulates the acquisition of gliogenic competence by neural stem cells

Mammalian neural stem/progenitor cells (NSPCs) sequentially generate neurons and glia during CNS development. Here we identified miRNA-153 (miR-153) as a modulator of the temporal regulation of NSPC differentiation. Overexpression (OE) of miR-153 delayed the onset of astrogliogenesis and maintained NSPCs in an undifferentiated state in vitro and in the developing cortex. The transcription factors nuclear factor I (NFI) A and B, essential regulators of the initiation of gliogenesis, were found to be targets of miR-153. Inhibition of miR-153 in early neurogenic NSPCs induced precocious gliogenesis, whereas NFIA/B overexpression rescued the anti-gliogenic phenotypes induced by miR-153 OE. Our results indicate that miR-mediated fine control of NFIA/B expression is important in the molecular networks that regulate the acquisition of gliogenic competence by NSPCs in the developing CNS

Altered structural connectivity networks in a mouse model of complete and partial dysgenesis of the corpus callosum

Corpus callosum dysgenesis (CCD) describes a collection of brain malformations in which the main fiber tract connecting the two hemispheres is either absent (complete CCD, or 'agenesis of the corpus callosum') or reduced in size (partial CCD). Humans with these neurodevelopmental disorders have a wide range of cognitive outcomes, including seemingly preserved features of interhemispheric communication in some cases. However, the structural substrates that could underlie this variability in outcome remain to be fully elucidated. Here, for the first time, we characterize the global brain connectivity of a mouse model of complete and partial CCD. We demonstrate features of structural brain connectivity that model those predicted in humans with CCD, including Probst bundles in complete CCD and heterotopic sigmoidal connections in partial CCD. Crucially, we also histologically validate the recently predicted ectopic sigmoid bundle present in humans with partial CCD, validating the utility of this mouse model for fine anatomical studies of this disorder. Taken together, this work describes a mouse model of altered structural connectivity in variable severity CCD and forms a foundation for future studies investigating the function and mechanisms of development of plastic tracts in developmental disorders of brain connectivity