Semi-quantitative RT-PCR for comparison of mRNAs in cells with different amounts of housekeeping gene transcripts

A simple method is reported here for the semi-quantitative assay of mRNAs in the presence of an exogenous mRNA (pBR322 transcript) as a standard. This method uses the co-reverse transcription and co-amplification (co RT-PCR) of the target and standard mRNAs. This procedure enables transcripts to be compared when the differentiation process affects the transcription pattern of the beta-actin housekeeping gene, a commonly used internal standard. This method is sensitive and avoids constructing internal competitive RNA standards. As an example, it is shown that beta-actin transcription decreases and type V adenylyl cyclase transcription increases in adipocytes, when compared to preadipocytes.

Critical level and detection limit: performance measures for PCR-based assays

In clinical diagnostic work, sensitivity and specificity are key assay features. In this note we introduce two clinically relevant statistical assay performance measures, the critical level (CL), and the detection limit (DL) for the PCR-based assay. To allow for easy access to these characteristics a Windows-based program has been developed. The application of CL and DL by means of examples is described.

Alternative splicing of insulin-like growth factor I mRNA is developmentally regulated in the rat and mouse with preferential exon 2 usage in the mouse

The synthesis of an IGF-I complementary RNA (cRNA) standard containing the primer sequences for each of the four IGF-I mRNA alternative transcript forms (class 1Ea, 1Eb, 2Ea and 2Eb) and a polyA+ tail allowed the determination of the absolute abundance of each form in growing rats and mice by quantitative RT-PCR. In rat liver, class 1Ea mRNA was the most abundant form representing 90% of the total IGF-I mRNA. Though the relative proportion was maintained, the absolute abundance was maximal at 4 weeks of age and had declined by 6 weeks. In contrast, class 2Ea mRNA was the predominant transcript in mouse liver (70% of total IGF-I mRNA) and the 2Eb mRNA form was also 10-fold higher than that detected in rat liver. These results suggest that rats and mice differ both in their transcription initiation at two leader exons and in their alternative splicing activities for exon 5.