Tet1 Isoforms Differentially Regulate Gene Expression, Synaptic Transmission, and Memory in the Mammalian Brain

Area of Science:

• Neuroscience
• Epigenetics
• Molecular Biology

Background:

• Dynamic regulation of DNA methylation is crucial for neuronal function, memory, and adaptive behaviors.
• Ten-eleven translocation 1 (TET1) enzymes mediate DNA demethylation by oxidizing 5-methylcytosine (5mC) to 5-hydroxymethylcytosine (5hmC).
• Previous research on TET1's role in the nervous system yielded contradictory findings, potentially due to the existence of multiple TET1 isoforms.

Purpose of the Study:

• To investigate the distinct roles of the two TET1 isoforms (full-length and N-terminally truncated) in the adult mouse brain.
• To determine the cell-type specificity and functional impact of each TET1 isoform on gene expression, synaptic transmission, and memory.

Main Methods:

• Demonstrated co-expression of both full-length (Tet1) and shorter (Tet1) transcripts in the adult mouse brain.
• Utilized viral-mediated, isoform- and neuron-specific molecular tools to repress individual Tet1 transcripts.
• Analyzed changes in gene expression, basal synaptic transmission, and hippocampal-dependent memory in male mice.

Main Results:

• Tet1 is the predominantly expressed isoform in neurons, while Tet1 is expressed at lower levels and enriched in glia.
• Repression of each Tet1 isoform led to distinct gene ensemble dysregulation and contrasting alterations in basal synaptic transmission.
• Tet1 repression enhanced, whereas Tet1 repression impaired, hippocampal-dependent memory in male mice.

Conclusions:

• The two TET1 isoforms exhibit cell-type-specific expression patterns in the brain.
• Each TET1 isoform plays a distinct and non-redundant role in regulating gene expression, synaptic plasticity, and memory formation.
• Understanding the differential functions of TET1 isoforms is critical for comprehending epigenetic regulation in the mammalian central nervous system.