IsomiR

[1] It has been found that isomiR expression profiles can also exhibit race, population, and sex dependencies.

However, the advent of deep sequencing has now allowed researchers to detect a huge variability in miRNA biogenesis, meaning that from the same miRNA precursor many different sequences can be generated potentially have different targets,[3][4][5] or even lead to opposite changes in mRNA expression.

[6][7][8][9] The variations are mainly generated by a shift of Drosha and Dicer in the cleavage site, but also by nucleotide additions at the 3'-end,[10] resulting in new sequences different from the annotated miRNA.

[8][9] Moreover, it has been proven that isomiRs are not caused by RNA degradation during sample preparation for next generation sequencing.

[16] Some studies have tried to explain the miRNA diversity by structural bases of precursors but without clear results.