Patent ID: 7544471

Claim:
A method of preparing labeled miRNA from a wax-embedded tissue specimen comprising: removing wax from the wax embedded tissue specimen, digesting the tissue specimen to provide a digested tissue specimen, purifying a plurality of miRNAs from the digested tissue specimen to provide a purified miRNA fraction, treating the purified miRNA fraction with a phosphatase to provide a sample containing a plurality of dephosphorylated miRNAs, heating the sample to at least 80° C. under conditions including at least 40% DMSO; and contacting the sample with RNA ligase in the presence of a labeled substrate under conditions sufficient to result in coupling of the labeled substrate to the miRNA in the sample to provide labeled miRNA, the conditions including a DMSO concentration in the range from about 20% to about 30%, wherein the labeled substrate comprises an observable label moiety and a nucleotide moiety, the nucleotide moiety having a 5′ phosphate and a 3′ terminus, the observable label moiety directly attached to the 3′ terminus, wherein the observable label moiety is selected from a chromogenic moiety or a fluorophore.