Identifying and understanding changes in cancer genomes is essential for the development of targeted therapeutics1. Here we analyse systematically more than 70 pairs of primary human colon tumours by applying next-generation sequencing to characterize their exomes, transcriptomes and copy-number alterations. We have identified 36,303 protein-altering somatic changes that include several new recurrent mutations in the Wnt pathway gene TCF7L2, chromatin-remodelling genes such as TET2 and TET3 and receptor tyrosine kinases including ERBB3. Our analysis for significantly mutated cancer genes identified 23 candidates, including the cell cycle checkpoint kinase ATM. Copy-number and RNA-seq data analysis identified amplifications and corresponding overexpression of IGF2 in a subset of colon tumours. Furthermore, using RNA-seq data we identified multiple fusion transcripts including recurrent gene fusions involving R-spondin family members RSPO2 and RSPO3 that together occur in 10% of colon tumours. The RSPO fusions were mutually exclusive with APC mutations, indicating that they probably have a role in the activation of Wnt signalling and tumorigenesis. Consistent with this we show that the RSPO fusion proteins were capable of potentiating Wnt signalling. The R-spondin gene fusions and several other gene mutations identified in this study provide new potential opportunities for therapeutic intervention in colon cancer.

The mutation brachypodism (bp) alters the length and number of bones in the limbs of mice but spares the axial skeleton. It illustrates the importance of specific genes in controlling the morphogenesis of individual skeletal elements in the tetrapod limb. We now report the isolation of three new members of the transforming growth factor-beta (TGF-beta) superfamily (growth/differentiation factors (GDF) 5,6 and 7) and show by mapping, expression patterns and sequencing that mutations in Gdf5 are responsible for skeletal alterations in bp mice. GDF5 and the closely related GDF6 and GDF7 define a new subgroup of factors related to known bone- and cartilage-inducing molecules, the bone morphogenetic proteins (BMPs). Studies of Bmp5 mutations in short ear mice have shown that at least one other BMP gene is also required for normal skeletal development. The highly specific skeletal alterations in bp and short ear mice suggest that different members of the BMP family control the formation of different morphological features in the mammalian skeleton.

Cancer stem cells (CSCs) have been hypothesized to represent the driving force behind tumour progression and metastasis, making them attractive cancer targets. However, conclusive experimental evidence for their functional relevance is still lacking for most malignancies. Here we show that the leucine-rich repeat-containing G-protein-coupled receptor 5 (Lgr5) identifies intestinal CSCs in mouse tumours engineered to recapitulate the clinical progression of human colorectal cancer. We demonstrate that selective Lgr5 cell ablation restricts primary tumour growth, but does not result in tumour regression. Instead, tumours are maintained by proliferative Lgr5 cells that continuously attempt to replenish the Lgr5 CSC pool, leading to rapid re-initiation of tumour growth upon treatment cessation. Notably, CSCs are critical for the formation and maintenance of liver metastasis derived from colorectal cancers. Together, our data highlight distinct CSC dependencies for primary versus metastasic tumour growth, and suggest that targeting CSCs may represent a therapeutic opportunity for managing metastatic disease.

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Mouse embryos bearing hypomorphic and conditional null Fgf8 mutations have small and abnormally patterned telencephalons. We provide evidence that the hypoplasia results from decreased Foxg1 expression, reduced cell proliferation and increased cell death. In addition, alterations in the expression of Bmp4, Wnt8b, Nkx2.1 and Shh are associated with abnormal development of dorsal and ventral structures. Furthermore, nonlinear effects of Fgf8 gene dose on the expression of a subset of genes, including Bmp4 and Msx1, correlate with a holoprosencephaly phenotype and with the nonlinear expression of transcription factors that regulate neocortical patterning. These data suggest that Fgf8 functions to coordinate multiple patterning centers, and that modifications in the relative strength of FGF signaling can have profound effects on the relative size and nature of telencephalic subdivisions.KEY WORDS: Fgf8, Forebrain, Patterning, Mouse Development 133, 1831Development 133, -1844Development 133, (2006 The previous studies concentrated on the phenotype of the Fgf8 TelKO and Fgf8 Null/Neo mutant telencephalon beginning at E10.5 and did not examine primary phenotypes in the neural plate or just following neural tube closure. Because prosencephalic expression of Fgf8 begins at neural plate stages (Crossley and Martin, 1995;Shimamura and Rubenstein, 1997; Crossley et al., 2001), it is essential to investigate the mutant phenotypes shortly after this stage to elucidate the mechanisms underlying Fgf8 TelKO and Fgf8 Null/Neo phenotypes. Therefore, here we report studies of Fgf8 dose-dependent effects on neural plate and early post-neurulation stage embryos. Furthermore, Storm et al. (Storm et al., 2003) focused on the effects of reducing Fgf8 dose on telencephalic midline development; here we concentrate on the effect of reducing Fgf8 dose on telencephalic patterning centers, regionalization and growth.We report our finding that specification of the prosencephalon is intact in Fgf8 mutants; however, a major reduction in Foxg1 expression, a reduced mitotic index, and increased apoptosis contribute to telencephalic hypoplasia. We also demonstrate that Fgf8 regulates the expression of Bmp4, Wnt8b and Shh, which in turn affect patterning of both dorsal and ventral structures. Nonlinear effects of Fgf8 dose on Bmp4 expression correlate with a holoprosencephaly phenotype and alterations in the expression of transcription factors that regulate neocortical patterning. The nexus of regulatory interactions between patterning centers that control gradients of transcription factor expression demonstrates that modifications in the relative strength of FGF/BMP/WNT/SHH signaling have profound effects on the relative size and nature of telencephalic subdivisions that are likely to contribute to their phylogenetic and intra-individual diversity. MATERIALS AND METHODS Mice and genotypingAll Fgf8 mutant alleles were maintained on a mixed 129/CD1 Swiss genetic background. Fgf8 Null/+ )embryos. PCR genotyping was performed as described pr...