Requirements in screening cDNA libraries for new genes and solutions offered by SBH technology

摘要

Under different assumptions about the total number of genes, the number of housekeeping and tissue-specific genes, and the difference in the number of mRNAs per cell for functional and nonfunctional genes, significantly different results can be expected from screening random cDNA clones. We have developed gene expression models as a guide for interpretation of experimental results. For statistical, biological, and technical reasons, the search for 100,000 plus genes and discrimination between nonfunctional, housekeeping, and tissue-specific genes requires the analysis of up to 10 million clones from 20 to 50 tissues. Oligonucleotide hybridization of dense clone blots is an inexpensive and fast way to screen such large clone sets. Our preliminary results on control clones and thousands of cDNA clones from an infant brain library demonstrate the feasibility of the method. We present several models of gene expression and analyze the main factors which can influence the hunt for new genes via the screening of random cDNA libraries. The basic steps in the preparation and use of dense DNA dot arrays are described, and some results that demonstrate the feasibility and efficiency of gene inventorying by oligonucleotide hybridization are presented. Furthermore, partial SBH and single-pass gel sequencing are compared and a gene analysis scheme that combines the two approaches is discussed.