The main cell of origin of the Sonic hedgehog (SHH) subgroup of medulloblastoma (MB) is granule cell precursors (GCPs), a SHH-dependent transient amplifying population in the developing cerebellum. SHH-MBs can be further subdivided based on molecular and clinical parameters, as well as location since SHH-MBs occur preferentially in the lateral cerebellum (hemispheres). Our analysis of adult patient data suggests that tumors with Smoothened (SMO) mutations form more specifically in the hemispheres than those with Patched 1 (PTCH1) mutations. Using sporadic mouse models of SHH-MB with the two mutations commonly seen in adult MB, constitutive activation of Smo (SmoM2) or loss-of-Ptch1, we found that regardless of timing of induction or type of mutation, tumors developed primarily in the hemispheres with SmoM2-mutants indeed showing a stronger specificity. We further uncovered that GCPs in the hemispheres are more susceptible to high level SHH signaling compared to GCPs in the medial cerebellum (vermis), as more SmoM2 or Ptch1-mutant hemisphere cells remain undifferentiated and show increased tumorigenicity when transplanted. Finally, we identified location-specific GCP gene expression profiles, and found that deletion of the genes most highly expressed in the hemispheres (Nr2f2) or vermis (Engrailed1) showed opposing effects on GCP differentiation. Our studies thus provide new insights into intrinsic differences within GCPs that impact on SHH-MB progression.
Lateral cerebellum is preferentially sensitive to high sonic hedgehog signaling and medulloblastoma formation.
Specimen partView Samples
We report liver transcript profiling by RNA sequencing of Atp7b-/- and wild type mice at six weeks of age. Transcriptional network analysis of RNA-seq data reveals a highly interconnected network of transcriptional activators with over-representation of zinc-dependent and zinc-responsive transcription factors. Overall design: Wild type and Atp7b-/- Mice were maintained on strain C57BL x 129S6/SvEv. Housing was in shoebox cages and fed Mazuri Rodent diet (PMI Nutrition, Inc., Richmond, Indiana), containing 16 ppm Cu, 100 ppm Zn, and 235 ppm Fe and water ad libitum, with a 12-hour light/dark cycle. Six-week-old mice of both sexes were used for transcriptomic studies. Animals were sacrificed by carbon dioxide asphyxiation and liver tissue was harvested for RNA isolation. RNA sequencing was performed at the National Center for Genome Resources (NCGR) using the GAIIx platform. Average read quality was 38. An initial dataset was generated using two wild type and two Atp7b-/- samples with singleton 1x54 runs with 15,823,058; 8,149,631; 22,931,967 and 9,538,147 reads. A second paired end (2x54) dataset was generated to augment the initial singleton dataset with one wild type and one Atp7b-/- run resulting in 36,360,686 and 38,366,743 reads, respectively.
Altered zinc balance in the Atp7b<sup>-/-</sup> mouse reveals a mechanism of copper toxicity in Wilson disease.
Sex, Specimen part, Cell line, SubjectView Samples
Wilson disease (WD) is a severe metabolic disorder caused by genetic inactivation of copper-transporting ATPase ATP7B. In WD, copper accumulates in several tissues, particularly in the liver, inducing marked time-dependent pathological changes. To identify initial events in the copper-dependent development of liver pathology we utilized the Atp7b-/- mice, an animal model for WD. Analysis of mRNA from livers of control and Atp7b-/- 6 weeks-old mice using oligonucleotide arrays revealed specific changes of the transcriptome at this stage of copper accumulation. Few messages (29 up-regulated and 46 down-regulated) change their abundance more than 2-fold pointing to the specific effect of copper on gene expression/mRNA stability. The gene ontology analysis revealed copper effects on distinct metabolic pathways.
High copper selectively alters lipid metabolism and cell cycle machinery in the mouse model of Wilson disease.
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Mammalian genomes encode several hundred KrÃ¼ppel-associated box zinc finger proteins (KRAB-ZFPs) that bind DNA in a sequence-specific manner through tandem arrays of C2H2-type zinc fingers and repress transcription via KRAB-dependent recruitment of the silencing cofactor KAP1. The KRAB-ZFP family rapidly amplified and diversified in mammals by segmental gene duplications, mutations, and zinc finger rearrangements likely in response to continued transposable element invasions, but the biological functions and in vivo requirement of these proteins has gone largely unexplored. We determined the genomic binding sites of 61 murine KRAB-ZFPs and genetically deleted five large KRAB-ZFP gene clusters encoding more than 100 of the approximately 360 mouse KRAB-ZFPs. We demonstrate that most KRAB-ZFPs bind to specific retrotransposon families and that many of these retrotransposons are transcriptionally activated in KRAB-ZFP cluster KO ESCs, licensing retrotransposon-derived enhancers to activate nearby genes. Overall design: RNA-seq analysis of KRAB-ZFP cluster KO ES cells and tissues.
KRAB-zinc finger protein gene expansion in response to active retrotransposons in the murine lineage.
Age, Specimen part, Cell line, SubjectView Samples
Bivalent histone domains have been proposed to contribute to pluripotency in embryonic stem cells, suggesting an epigenetic mechanism may regulate stem cell behavior in general. Here we compare histone modifications in two other stem cells derived from the blastocyst. We show that extraembryonic stem cells have little repressive lysine 27 trimethylation and few bivalent domains. Thus, bivalent domains are not a common mechanism for maintaining the undifferentiated state in blastocyst-derived stem cells and alternative mechanisms must mediate transcriptional repression in extraembryonic cells. We show that lysine 9 trimethylation, but not DNA methylation, is likely to fulfill this role. Intriguingly, although we do detect bivalent domains in pluripotent cells in the early mouse embryo, the epigenetic status of extraembryonic cells does not entirely reflect their in vitro stem cell counterparts. Therefore, differences in epigenetic regulation between lineage progenitors in vivo and in vitro may arise during selection for self-renewal in vitro.
Distinct histone modifications in stem cell lines and tissue lineages from the early mouse embryo.
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While the reprogramming factors OCT4, SOX2, KLF4, and MYC (OSKM) can reactivate the pluripotency network in terminally differentiated cells, they also regulate expression of non-pluripotency genes in other contexts, such as the mouse primitive endoderm. The primitive endoderm is an extraembryonic lineage established alongside the pluripotent epiblast in the blastocyst, and is the progenitor pool for extraembryonic endoderm stem (XEN) cells. Several studies have shown that endodermal genes are upregulated in fibroblasts undergoing reprogramming, although whether endodermal genes promote or inhibit acquisition of pluripotency is unclear. We show that, in fibroblasts undergoing conventional reprogramming, OSKM-induced expression of endodermal genes leads to formation of induced XEN (iXEN) cells, which possess key properties of blastocyst-derived XEN cells, including morphology, transcription profile, self-renewal, and multipotency. Our data show that iXEN cells arise in parallel to iPS cells, indicating that OSKM are sufficient to drive cells to two distinct fates during reprogramming. Overall design: Sequence-based mRNA transcriptional profiling of three different cell lines (MEF, XEN, iXEN) with multiple biological replicates, under two different growth medium conditions (ESC medium, XEN medium) for XEN and iXEN cells.
OSKM Induce Extraembryonic Endoderm Stem Cells in Parallel to Induced Pluripotent Stem Cells.
Specimen part, Treatment, SubjectView Samples
Stearoyl-CoA desaturase (SCD) is the rate-limiting enzyme catalyzing the conversion of saturated fatty acids palmitate and stearate to monounsaturated fatty acids palmitoleate and oleate. During adipocyte differentiation, SCD expression increases concomitantly with several transcription factors and lipogenic genes.
Inhibition of stearoyl-CoA desaturase-1 in differentiating 3T3-L1 preadipocytes upregulates elongase 6 and downregulates genes affecting triacylglycerol synthesis.
Specimen part, TreatmentView Samples
Saturated fatty acids (SFA) are widely thought to induce inflammation in adipose tissue (AT), while monounsaturated fatty acids (MUFA) are purported to have the opposite effect; however, it is unclear if individual SFA and MUFA behave similarly. Our goal was to examine adipocyte transcriptional networks regulated by individual SFA (palmitic acid, PA; stearic acid, SA) and MUFA (palmitoleic acid, PMA; oleic acid, OA).
Individual saturated and monounsaturated fatty acids trigger distinct transcriptional networks in differentiated 3T3-L1 preadipocytes.
Specimen partView Samples
ES cell lines were established from mouse embryos, which were homozygous for the Trim33-flox allele and carried the UbcCreERT2 transgene. Cells were cultured without feeder cells in the presence of LIF and 2i. Embryoid bodies (EBs) were generated using the ATCC protocol on low attachment dishes under differentiating conditions. EBs were induced with Tamoxifen at day 4 and harvested at day 7. Overall design: Investigate differentially expressed genes in control and Trim33-deficient embryoid bodies derived from mouse embryonic stem cells
Trim33 is required for appropriate development of pre-cardiogenic mesoderm.
Specimen part, Cell line, Subject, TimeView Samples