Mll Knockout Behavioral Testing
Objective: Compare contextual fear conditioning performance between Mll-deficient mice and wild-type controls to determine if histone methylation is required for long-term consolidation of contextual fear memories
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Protocol Steps
Contextual Fear Conditioning
Mice undergo contextual fear conditioning training
Note: Performed on Mll-deficient mice and wild-type control animals
View evidence from paper
“mice deficient in the H3K4-specific histone methyltransferase, Mll, displayed deficits in contextual fear conditioning relative to wild-type animals”
Hippocampal tissue collection at 1 hour post-conditioning
Hippocampal tissue collected 1 hour following contextual fear conditioning for histone modification analysis
Note: Measures H3K4 trimethylation and H3K9 dimethylation levels
View evidence from paper
“trimethylation of histone H3 at lysine 4 (H3K4), an active mark for transcription, is upregulated in hippocampus 1 h following contextual fear conditioning”
Hippocampal tissue collection at 24 hours post-conditioning
Hippocampal tissue collected 24 hours after context exposure alone and contextual fear conditioning
Note: Measures changes in H3K4 trimethylation and H3K9 dimethylation levels
View evidence from paper
“dimethylation of histone H3 at lysine 9 (H3K9), a molecular mark associated with transcriptional silencing, is increased 1 h after fear conditioning and decreased 24 h after context exposure alone”
Analysis of histone methylation at gene promoter regions
Examine H3K4 trimethylation at specific gene promoter regions (Zif268 and bdnf) with assessment of DNA methylation and MeCP2 DNA binding
Note: Zif268 DNA methylation levels returned to baseline at 24 hours
View evidence from paper
“fear learning triggered increases in H3K4 trimethylation at specific gene promoter regions (Zif268 and bdnf) with altered DNA methylation and MeCP2 DNA binding”
HDAC inhibition treatment
Administer sodium butyrate to inhibit histone deacetylases and assess effects on histone methylation patterns
Note: Results in increased H3K4 trimethylation and decreased H3K9 dimethylation in hippocampus following contextual fear conditioning
View evidence from paper
“inhibition of histone deacetylases (HDACs) with sodium butyrate (NaB) resulted in increased H3K4 trimethylation and decreased H3K9 dimethylation in hippocampus”