Project description:Recurrent mutations in chromatin modifiers are specifically prevalent in adolescent or adult patients with Sonic Hedgehog-associated medulloblastoma (SHH MB). Here, we report that mutations in the acetyltransferase CREBBP have opposing effects during the development of the cerebellum, the primary site of origin of SHH MB. Our data reveal that loss of Crebbp in cerebellar granule neuron progenitors (GNPs) during embryonic development of mice compromises GNP development, in part by downregulation of brain-derived neurotrophic factor (Bdnf). Interestingly, concomitant cerebellar hypoplasia was also observed in patients with Rubinstein-Taybi syndrome, a congenital disorder caused by germline mutations of CREBBP. By contrast, loss of Crebbp in GNPs during postnatal development synergizes with oncogenic activation of SHH signaling to drive MB growth, thereby explaining the enrichment of somatic CREBBP mutations in SHH MB of adult patients. Together, our data provide novel insights into time-sensitive consequences of CREBBP mutations and corresponding associations with human diseases. We used microarrays to detail the global programme of gene expression underlying the knockout of Crebbp in murine Shh medulloblastoma, acutely induced at postnatal stages of development.
Project description:Recurrent mutations in chromatin modifiers are specifically prevalent in adolescent or adult patients with Sonic Hedgehog-associated medulloblastoma (SHH MB). Here, we report that mutations in the acetyltransferase CREBBP have opposing effects during the development of the cerebellum, the primary site of origin of SHH MB. Our data reveal that loss of Crebbp in cerebellar granule neuron progenitors (GNPs) during embryonic development of mice compromises GNP development, in part by downregulation of brain-derived neurotrophic factor (Bdnf). Interestingly, concomitant cerebellar hypoplasia was also observed in patients with Rubinstein-Taybi syndrome, a congenital disorder caused by germline mutations of CREBBP. By contrast, loss of Crebbp in GNPs during postnatal development synergizes with oncogenic activation of SHH signaling to drive MB growth, thereby explaining the enrichment of somatic CREBBP mutations in SHH MB of adult patients. Together, our data provide novel insights into time-sensitive consequences of CREBBP mutations and corresponding associations with human diseases. We used microarrays to detail the global programme of gene expression underlying the knockout of Crebbp in murine granule neuron precursors, chronically induced at embryonic stages of development.
Project description:GLI2 overexpression is a hallmark in SHH subgroup of medulloblastoma (SHH MB). Here we identify the targetome of Gli2 in two mouse models of SHH MB: SmoM2 overexpression and Sufu;Spop double knockout MB.
Project description:GLI2 overexpression is a hallmark in SHH subgroup of medulloblastoma (SHH MB). Here we profile the transcriptome of two mouse models of SHH MB expressing high Gli2: SmoM2 overexpression and Sufu;Spop double knockout MB.
Project description:The childhood brain tumour medulloblastoma includes four subtypes with very different prognoses. Here, we show that paracrine signals driven by mutant Beta-Catenin in WNT-medulloblastoma â an essentially curable form of the disease â induce an aberrant fenestrated vasculature that permits the accumulation of high levels of intra-tumoural chemotherapy and a robust therapeutic response. In contrast, SHH-medulloblastoma â a less curable disease subtype â contains an intact blood brain barrier, rendering this tumour impermeable and resistant to chemotherapy. Remarkably, the medulloblastoma-endothelial cell paracrine axis can be manipulated in vivo, altering chemotherapy permeability and clinical response. Thus, medulloblastoma genotype dictates tumour vessel phenotype, explaining in part the disparate prognoses among medulloblastoma subtypes and suggesting an approach to enhance the chemoresponsiveness of other brain tumours. We used microarrays to detail the global program of gene expression within endothelial cells from normal mouse hindbrain and genetic mouse models of different medulloblastoma subtypes to identify and verify up-regulated and down-regulated genes Endothelial cells were isolated from adult mouse hindbrain and genetic mouse models of Wnt and Shh-medulloblastoma using Cd-144 and Cd-105 antibodies based magnetic sorting. RNA was extracted and used for hybridization on Affymetrix microarrays. We sought to identify changes in endothelial gene expression patterns based on the surrounding microenvironment, so we purified endothelial cells from normal mouse brain or tumors from genetic mouse models. These include the Shh-medulloblastoma model (Ptch+/-; Ink4c -/-) and Wnt-medulloblastoma model (Blbp-Cre; mutant Ctnnb1+/-; p53-/-; mutant Pik3ca +/-)
Project description:Sonic hedgehog (Shh) signaling plays a critical role in regulating cerebellum development by maintaining the physiological proliferation of granule neuron precursors (GNPs), and its dysregulation leads to the oncogenesis of medulloblastoma. O-GlcNAcylation (O-GlcNAc) of proteins is an emerging regulator of brain function that maintains normal development and neuronal circuitry. Here, we demonstrate that O-GlcNAc transferase (OGT) in GNPs mediate the cerebellum development, and the progression of the Shh-subgroup of medulloblastoma. Specifically, OGT regulates the proliferation of GNPs by activating the Shh signaling pathway via O-GlcNAcylation at S355 of GLI family zinc finger 2 (Gli2), which in turn promotes its deacetylation and transcriptional activity via dissociation from p300, a histone acetyltransferases (HATs). Inhibition of OGT via genetic ablation or chemical inhibition improves survival in a medulloblastoma mouse model. These data uncover a critical role for O-GlcNAc signaling in cerebellar development, and pinpoint a potential therapeutic target for Shh-associated medulloblastoma.
Project description:Medulloblastoma could be classified into four subtypes: Wnt, Shh, Group 3, and Group 4. Subtypes of medulloblastoma have distinct epigenetic properties. We report that a chromatin regulator SMARCA4/Brg1 controls a transcriptional program that specifically required for Shh-type medulloblastoma identity and proliferation. We show that Brg1 deletion significantly inhibited tumor formation and progression in a mouse medulloblastoma model. Genomic experiments indicate that Brg1 specifically coordinates with key transcription factors including Gli1, Atoh1, and REST to regulate the expression of both oncogenes and tumor suppressors. Shh-type medulloblastoma displays distinct H3K27me3 properties. We demonstrate that Brg1 modulates activities of H3K27me3 modifiers to regulate expression of medulloblastoma genes. Brg1 is important for the growth of a human medulloblastoma cell line and Brg1-regulated pathways are conserved in human Shh-type medulloblastoma. This study reveals a novel epigenetic mechanism that controls medulloblastoma development and provides a rationale for developing subtype-specific treatment strategies.
Project description:Medulloblastoma could be classified into four subtypes: Wnt, Shh, Group 3, and Group 4. Subtypes of medulloblastoma have distinct epigenetic properties. We report that a chromatin regulator SMARCA4/Brg1 controls a transcriptional program that specifically required for Shh-type medulloblastoma identity and proliferation. We show that Brg1 deletion significantly inhibited tumor formation and progression in a mouse medulloblastoma model. Genomic experiments indicate that Brg1 specifically coordinates with key transcription factors including Gli1, Atoh1, and REST to regulate the expression of both oncogenes and tumor suppressors. Shh-type medulloblastoma displays distinct H3K27me3 properties. We demonstrate that Brg1 modulates activities of H3K27me3 modifiers to regulate expression of medulloblastoma genes. Brg1 is important for the growth of a human medulloblastoma cell line and Brg1-regulated pathways are conserved in human Shh-type medulloblastoma. This study reveals a novel epigenetic mechanism that controls medulloblastoma development and provides a rationale for developing subtype-specific treatment strategies.