Whole-genome expression profiling through fragment display and combinatorial gene identification.

There is a growing demand for highly parallel gene expression analysis with whole genome coverage, high sensitivity and high accuracy. Open systems such as differential display are capable of analyzing most of the expressed genome but are not quantitative and generally require manual identification of differentially expressed genes by sequencing. Closed systems such as microarrays use gene-specific probes and are, therefore, limited to studying specific genes in well-characterized species. Here, we describe Tangerine, a PCR-based system that combines the scope and generality of open systems with a robust and immediate identification algorithm using publicly available sequence information. By combinatorial analysis of three independent and complete DNA indexing profiles, each displaying the complete set of expressed transcripts on capillary electrophoresis, the method allows transcripts to be simultaneously quantified and identified. The method is sensitive, accurate and reproducible, and is amenable to high-throughput automated operation.

Rapid genome sequencing with short universal tiling probes.

The increasing availability of high-quality reference genomic sequences has created a demand for ways to survey the sequence differences present in individual genomes. Here we describe a DNA sequencing method based on hybridization of a universal panel of tiling probes. Millions of shotgun fragments are amplified in situ and subjected to sequential hybridization with short fluorescent probes. Long fragments of 200 bp facilitate unique placement even in large genomes. The sequencing chemistry is simple, enzyme-free and consumes only dilute solutions of the probes, resulting in reduced sequencing cost and substantially increased speed. A prototype instrument based on commonly available equipment was used to resequence the Bacteriophage lambda and Escherichia coli genomes to better than 99.93% accuracy with a raw throughput of 320 Mbp/day, albeit with a significant number of small gaps attributed to losses in sample preparation.