MicroRNAs and their isomiRs function cooperatively to target common biological pathways

Area of Science:

• Molecular Biology
• Genomics
• Biochemistry

Background:

• MicroRNA (miRNA) variants, known as isomiRs, are frequently detected in deep-sequencing studies.
• The functional significance and biological relevance of isomiRs remain debated, despite non-random expression patterns suggesting regulation.

Purpose of the Study:

• To investigate the biological relevance and functional role of isomiRs.
• To develop and utilize a computational pipeline for analyzing miRNAs and isomiRs.

Main Methods:

• Ultra-deep miRNA sequencing across ten adult human tissues.
• Development of the miRNA-MATE analysis pipeline for miRNA and isomiR alignment and annotation.
• Experimental validation including AGO2 cleavage assessment, polyribosome association assays, and functional mRNA target determination via cell transfection.

Main Results:

• IsomiRs exhibit sequence and expression similarities to canonical miRNAs and are strongly correlated with their expression.
• A significant fraction of isomiRs may originate from AGO2 cleavage, independent of Dicer.
• IsomiRs and canonical miRNAs are equally associated with the translational machinery and target overlapping functional mRNA networks.

Conclusions:

• IsomiRs are biologically relevant molecules that function cooperatively with canonical miRNAs.
• IsomiRs and canonical miRNAs coordinate to regulate pathways of functionally related genes.
• This study elucidates the complexity of the miRNA-transcriptome and addresses the miRNA paradox of specific gene regulation with limited targeting sequences.