Analysis of multiple data sets after repetitive hybridizations on nylon membranes

Jan Lankelma^1,2, Jorrit J. Hornberg¹ , Richard R. de Haas² , Henk Dekker²

¹Department of Tumor Cell Biology, Vrije Universiteit, De Boelelaan 1087, 1081 HV Amsterdam;   ²VU Medical Center, Department of Medical Oncology, Room BR232, P.O. Box 7057, 1007 MB Amsterdam

The use of phosphorothioate cDNA has resulted in a more frequent use of cDNA arrays on nylon membranes. In our hands we could use the membranes at least ten times. Averaging of comparative gene expression in two samples allows reduction of the variation in hybridization efficiency and membrane cDNA concentration. We will show that based on statistical considerations up or down regulation by a factor two can reliably be measured when comparing two samples. The method is tested by demonstrating up and down regulation of genes involved in cell cycle regulation.