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Neuro-Oncology  2014;16(Suppl 3):iii28.
BACKGROUND: Tumor recurrence is the main cause of death for children with medulloblastoma, the most common malignant childhood brain tumor. The MYCN oncogene is a poor prognosis marker and is amplified in the molecularly defined SHH and Group 4 subgroups but rarely in WNT and Group 3 subgroups of human medulloblastoma. Recent findings on childhood brain tumor relapse mechanisms suggest spatiotemporal differences within these four subgroups. SOX9 is a transcription factor that is important for glial fate determination in the brain but has also been found to promote tumor metastasization. We previously showed how expression of SOX9 correlates well with human SHH tumors but only few scattered SOX9-positive cells are found in SHH-independent Group 3 and Group 4 human medulloblastoma. METHODS: In order to study recurrence processes experimentally, we used a previously described transgenic Tet-OFF (Glt1-tTA) inducible model of MYCN-driven SHH-independent medulloblastoma (GTML mouse). To recreate metastatic recurrence we further used a Tet-ON (SOX9-rtTA) model that drives MYCN expression from the SOX9 promoter upon doxycycline treatment. RESULTS: By crossing the GTML Tet-OFF model with a Tet-ON transgene we managed to study rare SOX9-positive tumor cells after SOX9-negative tumor cells were first depleted using doxycycline. SOX9-positive GTML cells were tumorigenic and reinitiated distant recurrences over time. The SOX9-positive cells further showed an increased resistance to MYCN-targeted therapies. Relapses showed similar histopathology but presented generally higher levels SOX9 as compared to primary GTML tumors. A similar correlation was found in Group 3 and Group 4 medulloblastoma patients where isolated metastases had consistently higher SOX9 levels as compared to corresponding primary tumors. Finally, we overexpressed SOX9 in normal cerebellar stem cells transduced with mutationally stabilized MYCN-T58A and injected them back into the cerebellum of adult mice. Surprisingly, SOX9-positive MYCN-T58A brain tumors migrated and developed in the forebrain in contrast to the cerebellar stem cells transduced with MYCN-T58A only. CONCLUSIONS: Our findings suggest that increased levels of SOX9 drives migration in MYCN-driven medulloblastoma. Rare SOX9-positive tumor cells show an increased therapy resistance and are alone capable of reinitiating childhood brain tumors. Further characterization of SOX9-positive cells in Group 3 and Group 4 tumors could help us understand what drives metastatic medulloblastoma relapse and could lead to new therapies directed against these particularly serious cell types. SECONDARY CATEGORY: Tumor Biology.
PMCID: PMC4144565
2.  Impact of an Exercise Intervention on DNA Methylation in Skeletal Muscle From First-Degree Relatives of Patients With Type 2 Diabetes 
Diabetes  2012;61(12):3322-3332.
To identify epigenetic patterns, which may predispose to type 2 diabetes (T2D) due to a family history (FH) of the disease, we analyzed DNA methylation genome-wide in skeletal muscle from individuals with (FH+) or without (FH−) an FH of T2D. We found differential DNA methylation of genes in biological pathways including mitogen-activated protein kinase (MAPK), insulin, and calcium signaling (P ≤ 0.007) and of individual genes with known function in muscle, including MAPK1, MYO18B, HOXC6, and the AMP-activated protein kinase subunit PRKAB1 in skeletal muscle of FH+ compared with FH− men. We further validated our findings from FH+ men in monozygotic twin pairs discordant for T2D, and 40% of 65 analyzed genes exhibited differential DNA methylation in muscle of both FH+ men and diabetic twins. We further examined if a 6-month exercise intervention modifies the genome-wide DNA methylation pattern in skeletal muscle of the FH+ and FH− individuals. DNA methylation of genes in retinol metabolism and calcium signaling pathways (P < 3 × 10−6) and with known functions in muscle and T2D including MEF2A, RUNX1, NDUFC2, and THADA decreased after exercise. Methylation of these human promoter regions suppressed reporter gene expression in vitro. In addition, both expression and methylation of several genes, i.e., ADIPOR1, BDKRB2, and TRIB1, changed after exercise. These findings provide new insights into how genetic background and environment can alter the human epigenome.
PMCID: PMC3501844  PMID: 23028138
3.  A Method to Study the Epigenetic Chromatin States of Rare Hematopoietic Stem and Progenitor Cells; MiniChIP–Chip 
Dynamic chromatin structure is a fundamental property of gene transcriptional regulation, and has emerged as a critical modulator of physiological processes during cellular differentiation and development. Analysis of chromatin structure using molecular biology and biochemical assays in rare somatic stem and progenitor cells is key for understanding these processes but poses a great challenge because of their reliance on millions of cells. Through the development of a miniaturized genome-scale chromatin immunoprecipitation method (miniChIP–chip), we have documented the genome-wide chromatin states of low abundant populations that comprise hematopoietic stem cells and immediate progeny residing in murine bone marrow. In this report, we describe the miniChIP methodology that can be used for increasing an understanding of the epigenetic mechanisms underlying hematopoietic stem and progenitor cell function. Application of this method will reveal the contribution of dynamic chromatin structure in regulating the function of other somatic stem cell populations, and how this process becomes perturbed in pathological conditions.
PMCID: PMC3396287  PMID: 21406121
Miniaturized chromatin immunoprecipitation assays; Microarray technology; Histone modifications; Stem and progenitor cells; Epigenetic regulation; Lineage commitment

Results 1-3 (3)