ADAR2 affects mRNA coding sequence edits with only modest effects on gene expression or splicing in vivo

Area of Science:

• Neuroscience
• Molecular Biology
• Genetics

Background:

• Adenosine deaminases acting on RNA (ADAR) enzymes, particularly ADAR2, play a critical role in RNA editing.
• ADAR2 converts adenosine to inosine in double-stranded RNA, generating diverse neurotransmitter receptor isoforms like Gria2.
• ADAR2 deficiency in mice leads to early mortality due to seizures, highlighting its vital function.

Purpose of the Study:

• To investigate the impact of ADAR2 deficiency on RNA editing and gene expression in the adult mouse frontal cortex.
• To analyze the consequences of ADAR2 loss-of-function on specific RNA editing sites, particularly in coding regions.

Main Methods:

• RNA sequencing (RNA-Seq) was employed to analyze the frontal cortices of ADAR2 knockout (Adar2(-/-)) Gria2(R/R) mice and their viable littermates.
• Comparative analysis of editing levels and gene expression profiles between ADAR2-deficient and control animals.

Main Results:

• A significant reduction in editing levels was observed at 56 distinct RNA sites in ADAR2-deficient mice, with most affected sites located in coding regions.
• ADAR2 deficiency had a limited impact on overall gene expression and splicing, with only two genes and three exons showing statistically significant changes.
• The Gria2 Q/R editing site, crucial for neuronal function, was analyzed in the context of ADAR2 deficiency.

Conclusions:

• ADAR2 is essential for site-specific RNA editing, significantly influencing protein-coding sequences.
• Despite its role in RNA editing, ADAR2 exhibits modest effects on global gene expression and splicing in the adult mouse frontal cortex.
• This study underscores the specific role of ADAR2 in RNA modification rather than broad transcriptional or splicing regulation.