Introns control stochastic allele expression bias

Area of Science:

• Genetics
• Molecular Biology
• Developmental Biology

Background:

• Monoallelic expression (MAE), or extreme allele bias, contributes to incomplete penetrance, missing heritability, and non-Mendelian diseases.
• In cancer, MAE correlates with reduced patient survival and increased tumor grade.
• Previous research suggested stochastic epigenetic silencing as the cause of MAE in a gene- and tissue-specific manner.

Purpose of the Study:

• Investigate the in vivo mechanisms of stochastic MAE using the model organism C. elegans.
• Determine the role of introns in regulating MAE.
• Explore the conservation of intron-mediated MAE regulation in humans.

Main Methods:

• Utilized C. elegans as an in vivo model system to study gene expression patterns.
• Quantified allele bias and MAE across various tissues.
• Performed bioinformatic analysis on human gene data to assess MAE in intronless genes.

Main Results:

• MAE and allele bias are prevalent across C. elegans tissues, existing on a spectrum from biallelic to monoallelic expression.
• The presence of introns significantly reduces MAE.
• Introns regulate MAE in a 5'-intron position-dependent manner across different genes, cell types, and promoters.
• Human intronless genes show a significant enrichment for MAE.

Conclusions:

• Introns play a crucial role in regulating MAE, acting as a protective mechanism against extreme allele bias.
• The discovered intron-mediated regulation of MAE is conserved across species, including humans.
• This mechanism may elucidate the basis of certain diseases caused by mutations within introns.