DNA methylation dynamics underlie metamorphic gene regulation programs in Xenopus tadpole brain

Area of Science:

• Developmental Biology
• Epigenetics
• Neuroscience

Background:

• DNA methylation is vital for gene regulation and brain development.
• Hormone signaling, especially thyroid hormone, can modulate DNA methylation patterns.
• Metamorphosis in Xenopus tadpoles is a thyroid hormone-dependent developmental process impacting the brain.

Purpose of the Study:

• To investigate genome-wide DNA methylation changes in the Xenopus tadpole brain during metamorphosis.
• To understand the relationship between DNA methylation and gene regulation in response to thyroid hormone.
• To identify specific epigenetic alterations in neurosecretory neurons during this developmental transition.

Main Methods:

• Methylated DNA Capture sequencing (MethylCap-seq) for genome-wide DNA methylation profiling.
• RNA sequencing to analyze gene expression changes.
• Immunohistochemistry to detect DNA demethylation intermediates and enzymes.

Main Results:

• A diverse landscape of DNA methylation was observed in the tadpole neural cell genome.
• Thousands of differentially methylated regions (DMRs) were identified across metamorphic stages, with demethylation predominating later in metamorphosis.
• Negative correlations were found between differentially expressed genes and DMRs in gene bodies and promoter-proximal regions.
• Increased levels of 5-hydroxymethylcytosine, 5-carboxymethylcytosine, and TET3 enzyme confirmed DNA demethylation during metamorphosis.

Conclusions:

• The tadpole neural cell genome undergoes substantial DNA methylation changes during metamorphosis.
• These epigenetic modifications are likely key drivers of chromatin structure and gene regulation shifts during development.
• Thyroid hormone signaling orchestrates significant epigenetic reprogramming in the developing brain.