Huntington's disease (HD) is an inherited neurodegenerative disorder caused by an expanded stretch of CAG trinucleotide repeats that results in neuronal dysfunction and death. We made induced pluripotent stem cell (iPSC) lines from HD patients and controls. Though no obvious effects of the CAG expansion on reprogramming or subsequent neural stem cell (NSC) production were seen, HD-NSCs showed CAG expansion-associated gene expression patterns and, upon differentiation, changes in electrophysiology, metabolism, cell adhesion, and ultimately an increased risk of cell death for both medium and longer CAG repeat expansions, with some deficits greater in cells from longer repeat HD NSCs. The HD180 lines were more vulnerable than control lines to cellular stressors and BDNF withdrawal using a range of assays across consortium laboratories. This HD iPSC collection represents a unique and well-characterized resource to elucidate disease mechanisms in HD and provides a novel human stem cell platform for screening new candidate therapeutics.
Induced pluripotent stem cells from patients with Huntington's disease show CAG-repeat-expansion-associated phenotypes.
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The bromodomain and extraterminal (BET) protein BRD4 is a therapeutic target in acute myeloid leukemia (AML). Here, we demonstrate that the AML maintenance function of BRD4 requires its interaction with NSD3, which belongs to a subfamily of H3K36 methyltransferases. Unexpectedly, AML cells were found to only require a short isoform of NSD3 that lacks the methyltransferase domain. We show that NSD3-short is an adaptor protein that sustains leukemia by linking BRD4 to the CHD8 chromatin remodeler, by using a PWWP chromatin reader module, and by employing an acidic transactivation domain. Genetic targeting of NSD3 or CHD8 mimics the phenotypic and transcriptional effects of BRD4 inhibition. Furthermore, BRD4, NSD3, and CHD8 colocalize across the AML genome, and each is released from super-enhancer regions upon chemical inhibition of BET bromodomains. These findings suggest that BET inhibitors exert therapeutic effects in leukemia by evicting BRD4-NSD3-CHD8 complexes from chromatin to suppress transcription. Overall design: PolyA+ (illumine TruSeq)/not-so-random (NSR) primers selected RNA-Seq for shRNA/sgRNA-expressing MLL-AF9 transformed acute myeloid leukemia cells (RN2).
NSD3-Short Is an Adaptor Protein that Couples BRD4 to the CHD8 Chromatin Remodeler.
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