Imprinting as Basis for Complex Evolutionary Novelties in Eutherians

Area of Science:

• Genetics
• Epigenetics
• Evolutionary Biology

Background:

• Genomic imprinting, a phenomenon causing monoallelic gene expression, is primarily observed in therian mammals.
• This epigenetic process presents evolutionary costs, including complex cellular architecture and risks of aneuploidy.
• Existing theories, like the kinship hypothesis, explain only parts of parent-of-origin gene expression.

Purpose of the Study:

• To review the multifaceted aspects of genomic imprinting.
• To argue that imprinting represents functional haploidy with benefits for gene dosage and cellular plasticity.
• To propose imprinting's role in evolutionary novelties like the placenta and eutherian brain expansion.

Main Methods:

• Review of existing literature on genomic imprinting.
• Analysis of single-cell transcriptome data.
• Examination of epigenetic research findings.

Main Results:

• Genomic imprinting is a complex, differentiated process, not fully explained by current theories.
• Imprinting enables precise gene dosage control for critical genes.
• It contributes to increased cellular diversity and plasticity.

Conclusions:

• Genomic imprinting is a functional haploidy crucial for mammalian evolution.
• Allele-specific gene regulation mechanisms underlying imprinting are key to evolutionary novelties.
• Imprinting likely facilitated the evolution of the placenta and the large eutherian brain.