What is miRNA*? Do I need to consider this in my profiling experiment?

miRNA and miRNA* are the two strands of the double-stranded RNA product of dicer processing of the stem loop precursor miRNA. miRNA is the ‘guide’ strand that eventually enters RISC. The miRNA* (with an asterisk) is the other ‘passenger’ strand. The level of miRNA* present in the cell is low (≤15% relative to the corresponding miRNA). In cases where there is a higher proportion of passenger strand present in the cell, the nomenclature miRNA-3p/miRNA-5p is used instead of miRNA/miRNA*. miRNA-3p is the miRNA derived from the 3' arm of the precursor miRNA. miRNA-5p is the miRNA derived from the 5' arm of the precursor miRNA.

You can read more about the miRNA composition in the cell in Landgraf, P., et.al., (2007), Cell, 129, 1401. If the passenger strand is known to be present in significant amounts (miRNA-3p/miRNA-5p), it may be worth including detection of this in the miRNA profiling experiment. You may decide to adopt a strategy of not including assays for miRNA* on the basis that these are likely to be less significant as mediators of gene regulation.