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Genome-wide analysis of alternative splicing in medulloblastoma identifies splicing patterns characteristic of normal cerebellar development.

ABSTRACT: Alternative splicing is an important mechanism for the generation of protein diversity at a post-transcriptional level. Modifications in the splicing patterns of several genes have been shown to contribute to the malignant transformation of different tissue types. In this study, we used the Affymetrix Exon arrays to investigate patterns of differential splicing between pediatric medulloblastomas and normal cerebellum on a genome-wide scale. Of the 1,262 genes identified as potentially generating tumor-associated splice forms, we selected 14 examples of differential splicing of known cassette exons and successfully validated 11 of them by reverse transcriptase PCR. The pattern of differential splicing of three validated events was characteristic for the molecular subset of sonic hedgehog (Shh)-driven medulloblastomas, suggesting that their unique gene signature includes the expression of distinctive transcript variants. Generally, we observed that tumor and normal fetal cerebellar samples shared significantly lower exon inclusion rates than normal adult cerebellum. We investigated whether tumor-associated splice forms were expressed in primary cultures of Shh-dependent mouse cerebellar granule cell precursors (GCP) and found that Shh caused a decrease in the cassette exon inclusion rate of five of the seven tested genes. Furthermore, we observed a significant increase in exon inclusion between postnatal days 7 and 14 of mouse cerebellar development, at the time when GCPs mature into postmitotic neurons. We conclude that inappropriate splicing frequently occurs in human medulloblastomas and may be linked to the activation of developmental signaling pathways and a failure of cerebellar precursor cells to differentiate.

SUBMITTER: Menghi F

PROVIDER: S-EPMC3060131 | biostudies-literature | 2011 Mar

REPOSITORIES: biostudies-literature

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Genome-wide analysis of alternative splicing in medulloblastoma identifies splicing patterns characteristic of normal cerebellar development.

Menghi Francesca F Jacques Thomas S TS Barenco Martino M Schwalbe Ed C EC Clifford Steven C SC Hubank Mike M Ham Jonathan J

Cancer research 20110119 6

Alternative splicing is an important mechanism for the generation of protein diversity at a post-transcriptional level. Modifications in the splicing patterns of several genes have been shown to contribute to the malignant transformation of different tissue types. In this study, we used the Affymetrix Exon arrays to investigate patterns of differential splicing between pediatric medulloblastomas and normal cerebellum on a genome-wide scale. Of the 1,262 genes identified as potentially generating ...[more]

PMID: 21248070

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Project description:Alternative pre-mRNA splicing critically contributes to the generation of protein variety in a tissue- and development-specific manner. Alterations in the normal pathways of alternative splicing (AS) have been associated with the growth and maintenance of several tumour types, and have been indicated as candidate bio-markers of tumour progression, metastasis and patient survival. In this study we applied genome-wide exon array technology to investigate AS events that may distinguish between human medulloblastoma and normal cerebellum. We initially investigated gene-level expression profiles to identify samples expressing gene signatures characteristic of previously described MB molecular subgroups. 3 medulloblastomas significantly over-expressed genes typically belonging to the Shh signalling pathway or associated with a granule cell progenitor status and were therefore classified as Shh-activated tumours (MB1). The remaining tumour samples were grouped together as medulloblastoma subset 2 (MB2). We then applied the Splicing Index algorithm and identified 1260 unique genes containing at least one candidate exon whose inclusion rate differed between different sample subgroups. Following the analysis of candidate event expression plots and gene structure annotation, we selected 14 examples of differential splicing of cassette exons and successfully validated 11 of them by semi-quantitative RT-PCR in a selection of the initial sample-set and subsequently in an independent set of 10 normal cerebellum and 20 medulloblastoma samples. Through the analysis of AS pathway in in vitro cultures of cerebellar granule cell progenitors (the putative cell of origin of least a subset of medulloblastomas), we showed that medulloblastoma-associated AS patterns could be indicative of a normal cerebellar undifferentiated phenotype and suggested that activation of oncogenic pathways during the development of the cerebellum may lead to a failure of neuronal differentiation also through the disruption of AS programs.

Dataset Information

Genome-wide analysis of alternative splicing in medulloblastoma identifies splicing patterns characteristic of normal cerebellar development.

Publications

Genome-wide analysis of alternative splicing in medulloblastoma identifies splicing patterns characteristic of normal cerebellar development.

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