Genomics of CpG methylation in developing and developed zebrafish

Area of Science:

• Epigenetics and Genomics
• Developmental Biology
• Molecular Biology

Background:

• DNA methylation is crucial for stable inheritance of chromatin modifications.
• Previous studies linked DNA methylation to gene silencing, primarily focusing on promoter regions.
• Genome-wide methylation patterns and their relation to gene transcription during vertebrate development remain unclear.

Purpose of the Study:

• To map the genome-wide distribution of DNA methylation in zebrafish embryos and differentiated tissues.
• To investigate the relationship between DNA methylation and gene transcription patterns across development.
• To identify novel methylation signatures and their correlation with gene expression and alternative splicing.

Main Methods:

• High-resolution methylome mapping of Danio rerio embryos and adult tissues.
• Unsupervised clustering analyses to classify tissues based on methylation patterns.
• Integration of whole-genome methylation data with public RNA-seq datasets for comparative analysis.

Main Results:

• Unique CpG methylation signatures identified in embryonic versus differentiated tissues, with distinct patterns in CpG islands and repetitive sequences.
• Discovery of a novel genome-wide exon methylation signature.
• Exonic methylation emerged as a stronger predictor of mRNA expression level than promoter methylation; transcriptionally skipped exons showed less methylation.

Conclusions:

• Zebrafish development is characterized by distinct tissue-specific methylation signatures.
• Exon methylation plays a significant role in regulating gene expression and alternative splicing.
• Complex interplay exists between DNA methylation, gene expression, alternative splicing, and developmental processes in zebrafish.