Project description:Lck-MyrAkt2 mice develop spontaneous thymic lymphomas at approximately 100-200 days of age, driven in part by a consitutatively-active AKT (due to myristoylation). mTOR Knock Down mice were crossed with Lck-MyrAkt postive mice to model the affects of decreasing mTOR activity on tumors with an activated PI3K/AKT/MTOR pathway. Lck-Akt/mTOR KD mice had prolonged survival compared to the Lck-Akt/mTOR WT mice. We used microarrays to compare the transcriptome in thymic lymphomas between Lck-Akt positive, mTOR WT and Lck-Akt positive, mTOR KD mice. Four thymic lymphomas from Lck-Akt/mTOR WT mice were compared to three thymic lymphomas from Lck-Akt/mTOR KD mice.
Project description:We used gene transcript profiling to gain a deeper understanding of the role of FBXW7 in tumor development and to determine the influence of mTOR inhibition by rapamycin on tumor transcriptome and biological functions. In comparison to tumors from p53 single heterozygous (p53+/-) mice, we find that tumors from Fbxw7/p53 double heterozygous (Fbxw7+/-p53+/-) mice show significant deregulation of cholesterol metabolic processes independent of rapamycin treatment, while cell cycle related genes were upregulated in tumors from placebo treated Fbxw7+/-p53+/- mice, but not in tumors from rapamycin treated Fbxw7+/-p53+/- mice. On the other hand, tumors from rapamycin treated Fbxw7+/-p53+/- mice were enriched for genes involved in the integrated stress response, an adaptive mechanism to survive in stressful environments. p53+/â and p53+/âFbxw7+/â mice were generated by crossing p53-/- mice with Fbxw7+/- mice. At 5 weeks of age, mice were exposed whole-body to a single dose of 4 Gy X-ray irradiation. Mice were divided randomly into two groups and treated with rapamycin or placebo. RNA was isolated from thymic lymphomas.
Project description:Inactivation of Pten occurs by multiple mechanisms including epigenetic silencing, point mutations, insertion, and deletion, which are tissue dependent. Although frequent loss of heterozygosity around Pten locus and plausible involvement of epigenetic silencing have been reported in radiation-induced thymic lymphomas, the frequency of Pten inactivation and the spectrum of causal aberrations have not yet been extensively characterized. Here, we assessed the principal mode of inactivation by comprehensively analyzing expression and alterations of Pten gene in 23 radiation-induced thymic lymphomas developed in B6C3F1 mice. We found no evidence for methylation-associated silencing of Pten gene. Instead, we found complex structural abnormalities in 8 lymphomas (35%) that included missense and nonsense mutations, 1- and 3-bp insertions, and focal deletions. Sequencing of deletion breakpoints suggested that illegitimate V(D)J recombination and microhomology-mediated rearrangement were responsible for the focal deletions. Seven out of these 8 lymphomas had biallelic alterations, and 4 of them did not express any Pten protein. These aberrations of Pten were well coincided with downstream Akt phosphorylation on Ser473. In conclusion, Pten inactivation, which is frequently biallelic and is caused by a variety of structural abnormalities but not by epigenetic silencing, is involved in radiation-induced lymphomagenesis. Three thymic lymphomas were analyzed by array-CGH method.
Project description:Following exposure to either high LET (linear energy transfer) or gamma radiation, the most frequently observed malignancies in both Trp53?P and Trp53+/- mice are mammary and skin tumours, and thymic lymphomas. To gain further insights into the landscape of radiation-induced tumours the overall frequency and size of insertions and deletions in expressed genes was assessed by RNA-Seq. RNA was extracted from 12 mammary tumours of a range of histologies that had been induced using 50cGy of either high- or low- LET. 5 normal mammary tissue controls were also analyzed. A further 8 thymic lymphomas induced by gamma or Fe-ion radiation exposure were also sequenced as part of this study.This data is part of a pre-publication release. For information on the proper use of pre-publication data shared by the Wellcome Trust Sanger Institute (including details of any publication moratoria), please see http://www.sanger.ac.uk/datasharing/
Project description:Inactivation of Pten occurs by multiple mechanisms including epigenetic silencing, point mutations, insertion, and deletion, which are tissue dependent. Although frequent loss of heterozygosity around Pten locus and plausible involvement of epigenetic silencing have been reported in radiation-induced thymic lymphomas, the frequency of Pten inactivation and the spectrum of causal aberrations have not yet been extensively characterized. Here, we assessed the principal mode of inactivation by comprehensively analyzing expression and alterations of Pten gene in 23 radiation-induced thymic lymphomas developed in B6C3F1 mice. We found no evidence for methylation-associated silencing of Pten gene. Instead, we found complex structural abnormalities in 8 lymphomas (35%) that included missense and nonsense mutations, 1- and 3-bp insertions, and focal deletions. Sequencing of deletion breakpoints suggested that illegitimate V(D)J recombination and microhomology-mediated rearrangement were responsible for the focal deletions. Seven out of these 8 lymphomas had biallelic alterations, and 4 of them did not express any Pten protein. These aberrations of Pten were well coincided with downstream Akt phosphorylation on Ser473. In conclusion, Pten inactivation, which is frequently biallelic and is caused by a variety of structural abnormalities but not by epigenetic silencing, is involved in radiation-induced lymphomagenesis.
Project description:Dnmt3b is a DNA methytransferase which is an enzyme that methylated genomic DNA which contributes to genomic stability and transcriptional regulation. We genetically inactivated Dnmt3b in the hematopoeitic compartment in the context of MYC overexpression and analysed the resulting thymic lymphomas.
Project description:Dnmt3b is a DNA methytransferase which is an enzyme that methylated genomic DNA which contributes to genomic stability and transcriptional regulation. We genetically inactivated Dnmt3b in the hematopoeitic compartment in the context of MYC overexpression and analysed the resulting thymic lymphomas.
Project description:The ERK5 MAP kinase signalling pathway was recently discovered as a driver of naïve pluripotency in mouse Embryonic Stem Cells (mESCs). However, the molecular functions of ERK5 in mESCs have not been investigated. Here, we employ combinatorial mESC proteomics to identify ERK5 target genes and substrates. Global proteomic profiling reveals ZSCAN4 and other 2-cell stage genes as transcriptional targets of the ERK5 pathway. ZSCAN4 expression is specifically induced by ERK5-dependent transcription of the core pluripotency factor KLF2. Additionally, ERK5 directly phosphorylates tandem KLF2 Thr-Pro/Ser-Pro motifs identified by phosphoproteomics to recruit the FBXW7-CUL1 E3 ligase, promoting KLF2 ubiquitylation and degradation. ERK5 phosphorylation of KLF2 thereby provides negative-feedback control to restrain transcriptional induction of ZSCAN4. Our data uncover an auto-regulatory module by which ERK5 co-opts KLF2 to pattern ZSCAN4 expression. This study provides the first molecular insight into ERK5 functions in mESCs, and suggests a novel role for ERK5 signalling in stem cell rejuvenation
Project description:Thymomas are one of the most rarely diagnosed malignancies. To better understand its biology and to identify therapeutic targets, we performed next-generation RNA sequencing. The RNA was sequenced from 13 thymic malignancies and 3 normal thymus glands. Validation of microRNA expression was performed on a separate set of 35 thymic malignancies. For cell-based studies, a thymoma cell line was used. Hierarchical clustering revealed 100% concordance between gene expression clusters and WHO subtype. A substantial differentiator was a large microRNA cluster on chr19q13.42 that was significantly overexpressed in all A and AB tumors and whose expression was virtually absent in the other thymomas and normal tissues. Overexpression of this microRNA cluster activates the PI3K/AKT/mTOR pathway. Treatment of a thymoma AB cell line with a panel of PI3K/AKT/mTOR inhibitors resulted in marked reduction of cell viability. A large microRNA cluster on chr19q13.42 is a transcriptional hallmark of type A and AB thymomas. Furthermore, this cluster activates the PI3K pathway, suggesting the possible exploration of PI3K inhibitors in patients with these subtypes of tumor. This work has led to the initiation of a phase II clinical trial of PI3K inhibition in relapsed or refractory thymomas. 13 thymic malignancies and 3 Normal Thymus RNA-Sequenced in triplicate