Comparison of glyceraldehyde-3-phosphate dehydrogenase and 28S-ribosomal RNA gene expression as RNA loading controls for northern blot analysis of cell lines of varying malignant potential.

Glyceraldehyde-3-phosphate dehydrogenase (GAPDH) has been a gene of choice in Northern blot analyses as an internal RNA loading control. We have investigated the expression of GAPDH and 28S-ribosomal RNA (28S rRNA) genes in mouse 10T1/2 cells and in a variety of tumorigenic and highly malignant metastatic cell lines derived from the 10T1/2 cell line. We observed that GAPDH mRNA levels varied markedly among the tumorigenic and highly malignant cell lines and were elevated in these cell lines when compared to the normal mouse 10T1/2 cells. In contrast, the levels of 28S rRNA did not significantly vary among the tumorigenic and highly malignant cell lines and were approximately at the same level as that found in the normal parental mouse 10T1/2 cell line. These observations indicate that much caution should be taken when using GAPDH gene expression as an RNA loading control for Northern blots. Based upon these observations, we recommend the use of 28S rRNA gene expression as a preferred RNA loading control for Northern blot analysis in which total RNA is used.