Tomato (Solanum lycopersicum) is a major crop plant and a model system for fruit development. Solanum is one of the largest angiosperm genera(1) and includes annual and perennial plants from diverse habitats. Here we present a high-quality genome sequence of domesticated tomato, a draft sequence of its closest wild relative, Solanum pimpinellifolium(2), and compare them to each other and to the potato genome (Solanum tuberosum). The two tomato genomes show only 0.6% nucleotide divergence and signs of recent admixture, but show more than 8% divergence from potato, with nine large and several smaller inversions. In contrast to Arabidopsis, but similar to soybean, tomato and potato small RNAs map predominantly to gene-rich chromosomal regions, including gene promoters. The Solanum lineage has experienced two consecutive genome triplications: one that is ancient and shared with rosids, and a more recent one. These triplications set the stage for the neofunctionalization of genes controlling fruit characteristics, such as colour and fleshiness

We sequenced 122 miRNAs in 10 primate species to reveal conservation characteristics of miRNA genes. Strong conservation is observed in stems of miRNA hairpins and increased variation in loop sequences. Interestingly, a striking drop in conservation was found for sequences immediately flanking the miRNA hairpins. This characteristic profile was employed to predict novel miRNAs using cross-species comparisons. Nine hundred and seventy-six candidate miRNAs were identified by scanning whole-genome human/mouse and human/rat alignments. Most of the novel candidates are conserved also in other vertebrates (dog, cow, chicken, opossum, zebrafish). Northern blot analysis confirmed the expression of mature miRNAs for 16 out of 69 representative candidates. Additional support for the expression of 179 novel candidates can be found in public databases, their presence in gene clusters, and literature that appeared after these predictions were made. Taken together, these results suggest the presence of significantly higher numbers of miRNAs in the human genome than previously estimated.

MicroRNAs are 20-to 23-nucleotide RNA molecules that can regulate gene expression. Currently >400 microRNAs have been experimentally identified in mammalian genomes, whereas estimates go up to 1000 and beyond. Here we show that many more mammalian microRNAs exist. We discovered novel microRNA candidates using two approaches: testing of computationally predicted microRNAs by a modified microarray-based detection system, and cloning and sequencing of large numbers of small RNAs from different human and mouse tissues. Together these efforts experimentally identified 348 novel mouse and 81 novel human microRNA candidate genes. Most novel microRNAs candidates are not conserved beyond mammals, and ∼10% are taxon-specific. Our analyses indicate that the entire microRNA repertoire is not remotely exhausted.

BackgroundStructural rearrangements form a major class of somatic variation in cancer genomes. Local chromosome shattering, termed chromothripsis, is a mechanism proposed to be the cause of clustered chromosomal rearrangements and was recently described to occur in a small percentage of tumors. The significance of these clusters for tumor development or metastatic spread is largely unclear.ResultsWe used genome-wide long mate-pair sequencing and SNP array profiling to reveal that chromothripsis is a widespread phenomenon in primary colorectal cancer and metastases. We find large and small chromothripsis events in nearly every colorectal tumor sample and show that several breakpoints of chromothripsis clusters and isolated rearrangements affect cancer genes, including NOTCH2, EXO1 and MLL3. We complemented the structural variation studies by sequencing the coding regions of a cancer exome in all colorectal tumor samples and found somatic mutations in 24 genes, including APC, KRAS, SMAD4 and PIK3CA. A pairwise comparison of somatic variations in primary and metastatic samples indicated that many chromothripsis clusters, isolated rearrangements and point mutations are exclusively present in either the primary tumor or the metastasis and may affect cancer genes in a lesion-specific manner.ConclusionsWe conclude that chromothripsis is a prevalent mechanism driving structural rearrangements in colorectal cancer and show that a complex interplay between point mutations, simple copy number changes and chromothripsis events drive colorectal tumor development and metastasis.

MicroRNAs (miRNAs) play an important role in development and regulate the expression of many animal genes by post-transcriptional gene silencing. Here we describe the cloning and expression of new miRNAs from zebrafish. By high-throughput sequencing of small-RNA cDNA libraries from 5-day-old zebrafish larvae and adult zebrafish brain we found 139 known miRNAs and 66 new miRNAs. For 65 known miRNAs and for 11 new miRNAs we also cloned the miRNA star sequence. We analyzed the temporal and spatial expression patterns for 35 new miRNAs and for 32 known miRNAs in the zebrafish by whole mount in situ hybridization and northern blotting. Overall, 23 of the 35 new miRNAs and 30 of the 32 known miRNAs could be detected. We found that most miRNAs were expressed during later stages of development. Some were expressed ubiquitously, but many of the miRNAs were expressed in a tissue-specific manner. Most newly discovered miRNAs have low expression levels and are less conserved in other vertebrate species. Our cloning and expression analysis indicates that most abundant and conserved miRNAs in zebrafish are now known.