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We describe a technology, the NanoString nCounter gene expression system, which captures and counts individual mRNA transcripts. Advantages over existing platforms include direct measurement of mRNA expression levels without enzymatic reactions or bias, sensitivity coupled with high multiplex capability, and digital readout. Experiments performed on 509 human genes yielded a replicate correlation coefficient of 0.999, a detection limit between 0.1 fM and 0.5 fM, and a linear dynamic range of over 500-fold. Comparison of the NanoString nCounter gene expression system with microarrays and TaqMan PCR demonstrated that the nCounter system is more sensitive than microarrays and similar in sensitivity to real-time PCR. Finally, a comparison of transcript levels for 21 genes across seven samples measured by the nCounter system and SYBR Green real-time PCR demonstrated similar patterns of gene expression at all transcript levels.

Here we present a finished sequence of human chromosome 15, together with a high-quality gene catalogue. As chromosome 15 is one of seven human chromosomes with a high rate of segmental duplication, we have carried out a detailed analysis of the duplication structure of the chromosome. Segmental duplications in chromosome 15 are largely clustered in two regions, on proximal and distal 15q; the proximal region is notable because recombination among the segmental duplications can result in deletions causing Prader-Willi and Angelman syndromes. Sequence analysis shows that the proximal and distal regions of 15q share extensive ancient similarity. Using a simple approach, we have been able to reconstruct many of the events by which the current duplication structure arose. We find that most of the intrachromosomal duplications seem to share a common ancestry. Finally, we demonstrate that some remaining gaps in the genome sequence are probably due to structural polymorphisms between haplotypes; this may explain a significant fraction of the gaps remaining in the human genome.

Nat. Biotechnol. 26, 317–325 (2008); published online 17 February 2008, corrected after print 16 May 2008 In the version of this article initially published, the list of authors omitted the final author, Krassen Dimitrov, and should have read as follows: Gary K Geiss1, Roger E Bumgarner2, Brian Birditt1, Timothy Dahl1, Naeem Dowidar1, Dwayne L Dunaway1, H Perry Fell1, Sean Ferree1, Renee D George1,5, Tammy Grogan1, Jeffrey J James1, Malini Maysuria1, Jeffrey D Mitton1, Paola Oliveri3,5, Jennifer L Osborn1,5, Tao Peng2, Amber L Ratcliffe1, Philippa J Webster1, Eric H Davidson3, Leroy Hood4 & Krassen Dimitrov4,5