"Per cell" normalization method for mRNA measurement by quantitative PCR and microarrays

Jun Kanno, Ken Ichi Aisaki, Katsuhide Igarashi, Noriyuki Nakatsu, Atsushi Ono, Yukio Kodama, Taku Nagao

Research output: Contribution to journalArticle

74 Citations (Scopus)

Abstract

Background: Transcriptome data from quantitative PCR (Q-PCR) and DNA microarrays are typically obtained from a fixed amount of RNA collected per sample. Therefore, variations in tissue cellularity and RNA yield across samples in an experimental series compromise accurate determination of the absolute level of each mRNA species per cell in any sample. Since mRNAs are copied from genomic DNA, the simplest way to express mRNA level would be as copy number per template DNA, or more practically, as copy number per cell. Results: Here we report a method (designated the "Percellome" method) for normalizing the expression of mRNA values in biological samples. It provides a "per cell" readout in mRNA copy number and is applicable to both quantitative PCR (Q-PCR) and DNA microarray studies. The genomic DNA content of each sample homogenate was measured from a small aliquot to derive the number of cells in the sample. A cocktail of five external spike RNAs admixed in a dose-graded manner (dose-graded spike cocktail; GSC) was prepared and added to each homogenate in proportion to its DNA content. In this way, the spike mRNAs represented absolute copy numbers per cell in the sample. The signals from the five spike mRNAs were used as a dose-response standard curve for each sample, enabling us to convert all the signals measured to copy numbers per cell in an expression profile-independent manner. A series of samples was measured by Q-PCR and Affymetrix GeneChip microarrays using this Percellome method, and the results showed up to 90 % concordance. Conclusion: Percellome data can be compared directly among samples and among different studies, and between different platforms, without further normalization. Therefore, "percellome" normalization can serve as a standard method for exchanging and comparing data across different platforms and among different labor-atories.

Original languageEnglish
Article number64
JournalBMC Genomics
Volume7
DOIs
Publication statusPublished - Mar 29 2006
Externally publishedYes

ASJC Scopus subject areas

  • Biotechnology
  • Genetics

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    Kanno, J., Aisaki, K. I., Igarashi, K., Nakatsu, N., Ono, A., Kodama, Y., & Nagao, T. (2006). "Per cell" normalization method for mRNA measurement by quantitative PCR and microarrays. BMC Genomics, 7, [64]. https://doi.org/10.1186/1471-2164-7-64