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Tlx3 promotes glutamatergic neuronal subtype specification through direct interactions with the chromatin modifier CBP.

ABSTRACT: Nervous system development relies on the generation of precise numbers of excitatory and inhibitory neurons. The homeodomain transcription factor, T-cell leukemia 3 (Tlx3), functions as the master neuronal fate regulator by instructively promoting the specification of glutamatergic excitatory neurons and suppressing the specification of gamma-aminobutyric acid (GABAergic) neurons. However, how Tlx3 promotes glutamatergic neuronal subtype specification is poorly understood. In this study, we found that Tlx3 directly interacts with the epigenetic co-activator cyclic adenosine monophosphate (cAMP)-response element-binding protein (CREB)-binding protein (CBP) and that the Tlx3 homeodomain is essential for this interaction. The interaction between Tlx3 and CBP was enhanced by the three amino acid loop extension (TALE)-class homeodomain transcription factor, pre-B-cell leukemia transcription factor 3 (Pbx3). Using mouse embryonic stem (ES) cells stably expressing Tlx3, we found that the interaction between Tlx3 and CBP became detectable only after these Tlx3-expressing ES cells were committed to a neural lineage, which coincided with increased Pbx3 expression during neural differentiation from ES cells. Forced expression of mutated Tlx3 lacking the homeodomain in ES cells undergoing neural differentiation resulted in significantly reduced expression of glutamatergic neuronal subtype markers, but had little effect on the expression on pan neural markers. Collectively, our results strongly suggest that functional interplay between Tlx3 and CBP plays a critical role in neuronal subtype specification, providing novel insights into the epigenetic regulatory mechanism that modulates the transcriptional efficacy of a selective set of neuronal subtype-specific genes during differentiation.

SUBMITTER: Shimomura A

PROVIDER: S-EPMC4530954 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:Cocaine-mediated repression of the histone methyltransferase (HMT) G9a has recently been implicated in transcriptional, morphological, and behavioral responses to chronic cocaine administration. Here, using a ribosomal affinity purification approach, we find that G9a repression by cocaine occurs in both Drd1 (striatonigral)- and Drd2 (striatopallidal)-expressing medium spiny neurons (MSNs). Conditional knockout and overexpression of G9a within these distinct cell types, however, reveals divergent behavioral phenotypes in response to repeated cocaine treatment. Our studies further indicate that such developmental deletion of G9a selectively in Drd2 neurons results in the unsilencing of transcriptional programs normally specific to striatonigral neurons, and the acquisition of Drd1-associated projection and electrophysiological properties. This partial striatopallidal to striatonigral ‘switching’ phenotype in mice indicates a novel role for G9a in contributing to neuronal subtype identity, and suggests a critical function for cell-type specific histone methylation patterns in the regulation of behavioral responses to environmental stimuli. Polyribosome associated mRNAs from 2-5 month old, age and sex matched Drd1-Cre; Drd1-TRAP; G9afl/fl and Drd1-TRAP; G9afl/fl, Drd2-Cre; Drd2-TRAP; G9afl/fl and Drd2-TRAP; G9afl/fl mice (n = 2-4 mice/genotype/drug treatment, 2 hours after the last of eight repeated cocaine injections of 20 mg/kg/day) were obtained as previously described. EGFP labeled ribosomes and associated mRNAs were immunoprecipitated using a mix of two monoclonal anti-GFP antibodies (50 μg of clones #19C8 and #19F7 for each IP, available at Sloan-Kettering Monoclonal Antibody Facility). Purified mRNA was amplified and processed for microarray and qPCR analysis using the Affymetrix two-cycle cDNA Synthesis kit (Affymetrix) as previously described. Affymetrix Mouse Genome 430 2.0 arrays were used in all experiments. Information regarding the array design and features can be found at www.affymetrix.com. Mouse Genome 430 2.0 arrays were scanned using the GeneChip Scanner 3000 (Affymetrix) and globally scaled to 150 using the Affymetrix GeneChip Operating Software (GCOS v1.4).

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Tlx3 promotes glutamatergic neuronal subtype specification through direct interactions with the chromatin modifier CBP.

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