Methods and reagents for preserving RNA in cell and tissue samples

Abstract

This specification relates to the field of molecular biology and provides novel methods and reagents for preserving and protecting the ribonucleic acid (RNA) content of samples from degradation prior to RNA isolation. This preservation may be accomplished without ultra-low temperature storage or disruption of the tissue.

What is claimed is:  
     
         1 . A method of preserving RNA comprising: 
 (i) obtaining an RNA-containing sample; and    (ii) treating the sample with an RNA preservation medium that infiltrates the sample and protects the RNA from nucleases.    
     
     
         2 . The method of  claim 1 , wherein the RNA preservation medium precipitates the RNA in the sample along with cellular protein in the sample and renders the RNA inaccessible to nucleases.  
     
     
         3 . The method of  claim 1 , wherein the RNA preservation medium comprises a salt.  
     
     
         4 . The method of  claim 3 , wherein the salt is a sulfate salt.  
     
     
         5 . The method of  claim 4 , wherein the salt is ammonium sulfate.  
     
     
         6 . The method of  claim 3 , wherein the salt is present in a concentration between 20 g/100 ml and the saturating concentration of the salt.  
     
     
         7 . The method of  claim 3 , wherein the salt is ammonium sulfate in a concentration of between 30 g/100 ml and 80 g/100 ml.  
     
     
         8 . The method of  claim 1 , wherein the RNA preservation medium comprises a combination of at least two salts.  
     
     
         9 . The method of  claim 8 , wherein the total salt concentration is between 20 g/100 ml and 100 g/100 ml.  
     
     
         10 . The method of  claim 1 , wherein the RNA preservation medium comprises a chelator of divalent cations.  
     
     
         11 . The method of  claim 1 , wherein the RNA preservation medium comprises a buffer.  
     
     
         12 . The method of  claim 1 , wherein the RNA preservation medium has a pH of between 4 and 8.  
     
     
         13 . The method of  claim 1 , wherein the sample is a suspension of cells.  
     
     
         14 . The method of  claim 1 , wherein the sample is a solid tissue sample.  
     
     
         15 . The method of  claim 1 , wherein the sample is a blood sample.  
     
     
         16 . The method of  claim 1 , wherein the sample is a water sample.  
     
     
         17 . The method of  claim 1 , wherein the sample comprises an entire organism.  
     
     
         18 . The method of  claim 17 , wherein the organism is a pathogen within a tissue sample or other organism.  
     
     
         19 . The method of  claim 1 , further comprising the step of isolating the preserved RNA.  
     
     
         20 . The method of  claim 19 , wherein the RNA is isolated at a temperature that is greater than −20° C.  
     
     
         21 . The method of  claim 19 , wherein the sample is stored prior to the isolation of the RNA.  
     
     
         22 . The method of  claim 21 , wherein the tissue is stored unfrozen at −20° C. to 45° C.  
     
     
         23 . The method of  claim 22 , wherein the sample is stored at greater than 0° C.  
     
     
         24 . A kit for preserving RNA within a sample and isolating the RNA from the sample comprising: 
 (i) an RNA preservation medium that infiltrates the sample and protects the RNA from nucleases; and    (ii) a reagent for performing an RNA extraction from the sample.    
     
     
         25 . The kit of  claim 24 , wherein the reagent for performing an RNA extraction is a reagent for performing a guanidinium-based RNA extraction.  
     
     
         26 . The kit of  claim 24 , wherein the reagent for performing an RNA extraction is a reagent for performing a lithium chloride-based RNA extraction.  
     
     
         27 . An RNA preservation medium that comprises a sulfate salt.  
     
     
         28 . The-RNA preservation medium of  claim 27 , wherein the sulfate salt is ammonium sulfate.  
     
     
         29 . The RNA preservation medium of  claim 27 , wherein the sulfate salt is present in a concentration between 20 g/100 ml and the saturating concentration of the salt.  
     
     
         30 . The RNA preservation medium of  claim 27 , wherein the sulfate salt is ammonium sulfate at a concentration of between 20 g/100 ml and 100 g/100 ml.  
     
     
         31 . The RNA preservation medium of  claim 27 , comprising a combination of at least two salts.  
     
     
         32 . The RNA preservation medium of  claim 31 , wherein the total salt concentration is between 20 g/100 ml and 100 g/100 ml.  
     
     
         33 . The RNA preservation medium of  claim 27 , comprising an organic solvent.  
     
     
         34 . The RNA preservation medium of  claim 27 , comprising a chelator of divalent cations.  
     
     
         35 . The RNA preservation medium of  claim 27 , comprising a buffer.  
     
     
         36 . The RNA preservation medium of  claim 27 , having a pH of between 4 and 8.  
     
     
         37 . A method of preserving RNA comprising: 
 (i) obtaining an RNA-containing sample;    (ii) providing a salt; and    (iii) admixing the sample and the salt in a liquid to form an RNA preservation composition that infiltrates the sample and protects the RNA from nucleases.    
     
     
         38 . The method of  claim 37 , wherein the sample is comprised in the liquid prior to admixing the sample with the salt.  
     
     
         39 . The method of  claim 37 , wherein the sample is a blood cell and the liquid is blood serum.  
     
     
         40 . The method of  claim 37 , wherein the liquid is water.  
     
     
         41 . The method of  claim 37 , wherein the liquid is a buffer.  
     
     
         42 . The method of  claim 37 , wherein the salt is in a solid form prior to admixing with the sample and the liquid.  
     
     
         43 . The method of  claim 37 , wherein the salt is comprised in the liquid prior to admixing the sample with the salt.  
     
     
         44 . The method of  claim 37 , wherein the salt is a sulfate salt.  
     
     
         45 . The method of  claim 44 , wherein the salt is ammonium sulfate.  
     
     
         46 . The method of  claim 37 , wherein the salt is present in solution at a final concentration of between 20 g/100 mL and the saturating concentration of the salt.  
     
     
         47 . The method of  claim 46 , wherein the salt is present in solution at a final concentration of between 30 g/100 mL and 80 g/100 mL.  
     
     
         48 . The method of  claim 37 , wherein the RNA preservation composition comprises at least two salts.  
     
     
         49 . The method of  claim 48 , wherein the total salt concentration is present in solution at a final concentration of between 20 g/100 mL and 100 g/100 mL.  
     
     
         50 . The method of  claim 37 , wherein the RNA preservation composition comprises a chelator of divalent cations.  
     
     
         51 . The method of  claim 37 , wherein said RNA preservation composition comprises a buffer.  
     
     
         52 . The method of claim S 1 , wherein said buffer has a pH between 4 and 8.  
     
     
         53 . The method of  claim 37 , further comprising the step of isolating the preserved RNA.  
     
     
         54 . The method of  claim 53 , wherein the RNA is isolated at a temperature that is greater than −20° C.  
     
     
         55 . The method of  claim 53 , wherein the sample is stored prior to the isolation of the RNA.  
     
     
         56 . The method of  claim 55 , wherein the sample is stored at temperatures greater than 0° C.  
     
     
         57 . A composition of matter comprising an RNA-containing sample, a liquid, and a salt in a concentration sufficient to protect the RNA from nucleases.  
     
     
         58 . The composition of  claim 57 , wherein the salt is a sulfate salt.  
     
     
         59 . The composition of  claim 58 , wherein the sulfate salt is ammonium sulfate.  
     
     
         60 . The composition of  claim 57 , comprising a combination of at least two salts.  
     
     
         61 . The composition of  claim 57 , comprising a buffer.  
     
     
         62 . The composition of  claim 61 , having a pH between 4 and 8.  
     
     
         63 . The composition of  claim 57 , comprising a chelator of divalent cations.