Crude biological derivatives competent for nucleic acid detection

Abstract

The invention relates generally to the fields of making biological unit lysates or admixtures of body fluids and of RNA analysis. More specifically, it relates to direct methods for the detection of a specific sequence of RNA in a biological unit, for example a virus, cell or tissue sample, or a body fluid, for example saliva, sputum, blood plasma, etc. More generally, the invention may be used to enzymatically manipulate and protect the RNA in lysate or bodily fluids for a number of applications.

Description

[0001] The government may own rights in the present invention pursuant to grant number R44 HL69718 from National Institutes of Health National Heart, Lung, and Blood Institute.BACKGROUND OF THE INVENTION [0002] 1. Field of the Invention [0003] The present invention relates generally to the fields of making biological unit lysates or admixtures of body fluids for RNA analysis. More specifically, it teaches a more direct method for the detection of a specific sequence of RNA in a biological unit, for example a virus, cell or tissue sample, or a body fluid, for example saliva, sputum, blood plasma, etc. More generally, the invention may be used to enzymatically manipulate and protect the RNA in lysate or bodily fluids for a number of applications. [0004] 2. Description of Related Art [0005] There are many molecular biology techniques that can be used to analyze RNA or RNA-containing samples. For example, reverse transcription followed by the polymerase chain reaction (RT-PCR) is one of...

AI Technical Summary

Benefits of technology

[0024] In some embodiments, the methods of the invention further comprise analyzing amplified DNA to determine the presence of and / or quantity of an RNA in the biological unit. There are many reasons that one might wish to do this, including but not limited to determining gene expression patterns for research, diagnostic, pharmacogenomics, and therapeutic applications. In many cases, these methods will comprise admixing an RNA control with the reaction mixture or the at least a portion of the extract prior to reverse transcription. Such an RNA control can be employed as an internal standard for quantifying the RNA in the biological unit and / or as an exogenously added positive control to assure that the reaction mixture is functioning properly. Of course, controls such as RNA or DNA controls can also be added to the reaction mixture prior to an amplification procedure, and it is also possible to use RNA or DNA controls and external standards or positive controls in the context of the invention. Those of skill understand that there are a wide variety of manners in which to employ controls in the context of the invention, and will be able to employ appropriate such controls for any specific format that they are practicing.

[0025] In some embodiments, the invention may be employed to determine differences in RNA levels between biological units comprised in two or more samples. Skilled molecular biologists understand that there are a wide variety of contexts in which such analysis may be employed. For example, they may be employed to study differences in gene expression during development, differences in gene expression between normal and diseased tissues, or differences in gene expression due to the contacting of a biological unit with some form of nucleic acid, protein, small molecule, antibody, or other substance. In some embodiments, the invention relates to methods of determining whether or not an siRNA with which the biological unit has been contacted has altered the concentration of one or more RNA in the biological unit. Such embodiments may comprise comparing the presence of and / or quantity of cDNA products from the biological unit contacted with the siRNA with cDNA products obtained from a biological unit not contacted with an siRNA or contacted with a negative control siRNA. Such methods also embody the determining of whether or not a compound with which the biological unit has been contacted has altered the concentration of one or more RNA in the biological unit, and may optionally comprise comparing the presence of and / or quantity of cDNA products from the biological unit contacted with the compound with cDNA products obtained from a biological unit not contacted with the compound or contacted with a control.

[0026] There are a wide variety of techniques that can be used to detect RNA or DNA generated by the methods of the invention and, in many embodiments, determining the presence of and / or quantifying RNA. For example the invention contemplates, but is not limited to, the use of a labeled probe or intercalating dye to determine the presence of and / or quantify the RNA. Labeled probes are typically nucleic acids that comprise one or more detectable labels. Such labels can be visual, fluorescent, chemical, enzymatic, or radioactive labels, or any other label suitable for the practice of the invention. Such labels can be detected by methods that are well known to those of skill in the art. In particular, some embodiments of the invention involve the use of dual-labeled fluorescent probes, such as TaqMan® Gene Expression Assays (Applied Biosystems), Scorpion™ (DxS; Manchester, UK), LUX™ (Invitrogen); Ampliflour™ (Chemicon), or molecular beacon probes. In other particular embodiments, the invention involves the use of intercalating dyes, including but not limited to SYBR® Green and ethidium bromide.

[0027] Some embodiments of the invention comprise amplifying RNA from the lysate or admixture. There are many cases where researchers have a limited amount of sample and the RNA isolated from the sample is not enough to perform the desired assay, and those of skill will be able to employ the invention in any such cases. A technique to which this often applies is in producing a labeled nucleic acid from the isolated RNA and then hybridizing the labeled nucleic acid to a microarray. The signals produced at each of the addresses of the microarray indicate the level of expression for each of the genes on the array. Thus, a snapshot is taken of the abundance for each of the genes probed by the array.

Problems solved by technology

Most other RNA isolation procedures lead to some loss of genomic DNA, and, therefore, genomic DNA could not be used as an internal standard.