Project description:Medulloblastomas (MBs) are the most common brain tumors in children. Some are thought to originate from cerebellar granule neuron progenitors (GNPs) that fail to undergo normal cell cycle exit and differentiation. Since microRNAs regulate numerous aspects of cellular physiology and development, we reasoned that alterations in miRNA expression might contribute to MB. We tested this hypothesis using two spontaneous mouse MB models with specific initiating mutations, Ink4c-/-; Ptch1+/- and Ink4c-/-; p53-/-. We found that 26 miRNAs showed increased expression and 24 miRNAs showed decreased expression in proliferating mouse GNPs and MBs relative to mature mouse cerebellum, regardless of genotype. Among the 26 overexpressed miRNAs, nine were encoded by the miR-17~92 cluster family, a group of microRNAs implicated as oncogenes in several tumor types. Analysis of human MBs demonstrated that three miR-17~92 cluster miRNAs (miR-92, miR-19a and miR-20) were also overexpressed in human MBs with a constitutively activated SHH signaling pathway, but not in other forms of the disease. To test whether the miR-17~92 cluster could promote MB formation, we enforced expression of these miRNAs in GNPs isolated from cerebella of postnatal (P) day P6 Ink4c-/-; Ptch1+/- mice. These, but not similarly engineered cells from Ink4c-/-; p53-/- mice, formed MBs in orthotopic transplants with complete penetrance. Interestingly, orthotopic mouse tumors ectopically expressing miR-17~92 lost expression of the wild-type Ptch1 allele. Our findings suggest a functional collaboration between the miR-17~92 cluster and the SHH signaling pathway in the development of MBs in mouse and man. Samples: purified CGNP-like mouse medulloblastoma cells; purified CGNPs from age day 6 (P6) mice; whole cerebellum from P6 mice; whole cerebellum from 1 month old mice. Each from three backgrounds (except tumors) - wt; Ptc+/-,Ink4c-/-; p53-/-,Ink4c-/-. Two to five biological replicates each.

Project description:Fragile X syndrome and tuberous sclerosis are genetic syndromes that both have a high rate of co-morbidity with autism spectrum disorders. Several lines of evidences suggest that these two monogenic disorders may converge at a molecular level through the dysfunction of activity-dependent synaptic plasticity. We utilized mouse models of these monogenic disorders to identify genome-wide transcriptional changes in cerebellum and blood and characterize the (dis-)similarity of their molecular signatures. Differentially expressed genes and enriched pathways were distinct for the two mouse models examined, with the exception of immune system related pathways. In the cerebellum of the Fmr1 knockout (Fmr1-KO) model, the neuroactive ligand receptor interaction pathway and gene sets associated with synaptic plasticity such as long term potentiation, gap junction, and axon guidance were the most significantly perturbed pathways. The phosphatidylinositol signaling pathway was significantly dysregulated in both blood and brain of Fmr1-KO mice. In both the blood and brain of the Tsc2 heterozygous mouse model, immune system related pathways, genes encoding ribosomal proteins, and glycolipid metabolism pathways were significantly perturbed. Our data suggest that distinct molecular pathways may be involved in autism spectrum disorders with known but different genetic causes, and that blood gene expression profiles of Fmr1-knockout and Tsc2+/- mice mirror some, but not all, of the perturbed molecular pathways in the brain. For the Fmr1-KO model, 10 mice, consisting of 5 KO and 5 WT mice, were profiled. Thus, 10 pairs of blood and cerebella samples were profiled. Likewise, for the Tsc+/- model, 3 transgenic and 3 WT mice were sacrificed and paired blood and cerebella samples were prepared for gene expression profiling. All samples were profiled using the Affymetrix Mouse Gene ST 1.0 ST arrays. Three factors—tissue (i.e. blood vs. cerebellum), treatment (i.e. knockout vs. wildtype), and genetic background (Fmr1-KO vs. Tsc2+/-)—were analyzed with analysis of variance (ANOVA). Subsequently, we compared blood and brain gene expression changes in Fmr1 and Tsc2 knockout mice models using WT littermates as controls using t-tests with unequal variances. The false discovery rate (FDR) was calculated using Storey and Tibshirani’s method.

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Mus musculus

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