The present disclosure provides non-naturally occurring miR-196a-2 miRNAs and non-naturally occurring miR-204 miRNAs. The non-naturally occurring miRNAs of the disclosure have mature strand sequences distinct from their endogenous counterparts. The disclosure also provides methods of selecting mature strand sequences that function optimally in non-naturally occurring miR-196a-2 miRNAs. The methods and compositions of the disclosure may be used to mediate gene silencing via the RNAi pathway.
