Abnormalities in WNT signaling are implicated in a broad range of developmental anomalies and also in tumorigenesis. Here we demonstrate that germline mutations in WTX (FAM123B), a gene that encodes a repressor of canonical WNT signaling, cause an X-linked sclerosing bone dysplasia, osteopathia striata congenita with cranial sclerosis (OSCS; MIM300373). This condition is typically characterized by increased bone density and craniofacial malformations in females and lethality in males. The mouse homolog of WTX is expressed in the fetal skeleton, and alternative splicing implicates plasma membrane localization of WTX as a factor associated with survival in males with OSCS. WTX has also been shown to be somatically inactivated in 11-29% of cases of Wilms tumor. Despite being germline for such mutations, individuals with OSCS are not predisposed to tumor development. The observed phenotypic discordance dependent upon whether a mutation is germline or occurs somatically suggests the existence of temporal or spatial constraints on the action of WTX during tumorigenesis.

BackgroundWe are investigating the molecular basis of melanoma by defining genomic characteristics that correlate with tumour phenotype in a novel panel of metastatic melanoma cell lines. The aim of this study is to identify new prognostic markers and therapeutic targets that might aid clinical cancer diagnosis and management.Principal FindingsGlobal transcript profiling identified a signature featuring decreased expression of developmental and lineage specification genes including MITF, EDNRB, DCT, and TYR, and increased expression of genes involved in interaction with the extracellular environment, such as PLAUR, VCAN, and HIF1a. Migration assays showed that the gene signature correlated with the invasive potential of the cell lines, and external validation by using publicly available data indicated that tumours with the invasive gene signature were less melanocytic and may be more aggressive. The invasion signature could be detected in both primary and metastatic tumours suggesting that gene expression conferring increased invasive potential in melanoma may occur independently of tumour stage.ConclusionsOur data supports the hypothesis that differential developmental gene expression may drive invasive potential in metastatic melanoma, and that melanoma heterogeneity may be explained by the differing capacity of melanoma cells to both withstand decreased expression of lineage specification genes and to respond to the tumour microenvironment. The invasion signature may provide new possibilities for predicting which primary tumours are more likely to metastasize, and which metastatic tumours might show a more aggressive clinical course.

The p53 protein is a pivotal tumor suppressor that is frequently mutated in many human cancers, although precisely how p53 prevents tumors is still unclear. To add to its complexity, several isoforms of human p53 have now been reported. The ⌬133p53 isoform is generated from an alternative transcription initiation site in intron 4 of the p53 gene (Tp53) and lacks the N-terminus. Elevated levels of ⌬133p53 have been observed in a variety of tumors. To explore the functions of ⌬133p53, we created a mouse expressing an N-terminal deletion mutant of p53 (⌬122p53) that corresponds to ⌬133p53. ⌬122p53 mice show decreased survival and a different and more aggressive tumor spectrum compared with p53 null mice, implying that ⌬122p53 is a dominant oncogene. Consistent with this, ⌬122p53 also confers a marked proliferative advantage on cells and reduced apoptosis. In addition to tumor development, ⌬122p53 mice show a profound proinflammatory phenotype having increased serum concentrations of interleukin-6 and other proinflammatory cytokines and lymphocyte aggregates in the lung and liver as well as other pathologies. Based on these observations, we propose that human ⌬133p53 also functions to promote cell proliferation and inflammation, one or both of which contribute to tumor development. (Blood. 2011;117(19): 5166-5177) Introduction p53 is most important for preventing cancers. We know this because mice deleted for the p53 gene (Trp53) are highly tumor prone 1 ; in humans, Li-Fraumeni syndrome, characterized by multiple tumor phenotypes, is the result of germline inherited mutations in the p53 gene (Tp53) 2 ; and most common human cancers contain mutations in Tp53 (www.p53.iarc.fr), generally rendering the protein functionally impaired. Ten isoforms of human p53 have been reported that are generated by the use of alternative translation initiation sites, splicing, or alternative promoters. [3][4][5][6][7][8][9] Two p53 isoforms (⌬40p53 and ⌬133p53) lack the N-terminus of p53, whereas 4 others (⌬40p53␤, ⌬40p53␥, ⌬133p53␤, and ⌬133p53␥) also lack part of the C-terminus beyond codon 331. In addition, 3 more isoforms have recently been described (⌬160p53, ⌬160p53␤, ⌬160p53␥) that use an alternative start codon at position 161 in the transcript for the ⌬133p53 isoform family. 8 The isoforms are generally expressed in a variable and to some extent tissue specific manner, although the ⌬133p53 isoform appears to be ubiquitous. 5 Aberrant expression of the ⌬133p53 isoforms occurs in a variety of tumors, including breast, 5 head and neck, 10 acute myeloid leukemia, 11 melanoma, 12 colon cancer, 13 and ovarian cancer, 14 suggesting that ⌬133p53 contributes to tumor formation. In zebrafish, the homolog of ⌬133p53 (⌬113p53) attenuates p53-dependent apoptosis by activating the homolog (bcl2l) of the antiapoptotic protein Bcl-xl, 15 and knockdown of ⌬113p53 using silencing RNA induced p53-dependent apoptosis. In another study, overexpression of ⌬133p53 extended the life span of normal human fibroblasts by inhibiting replicative senescen...

Chronic myeloid leukaemia (CML) develops when two genes, BCR on chromosome 22 and ABL on chromosome 9, recombine to form a hybrid BCR-ABL gene with leukaemogenic properties. The mechanism which underlies this recombination is unknown, but additional chromosome sites may be involved to form complex BCR-ABL rearrangements. The majority of breakpoints in BCR occur within a 5 kb major breakpoint cluster region, M-Bcr. Here, we show that the 3' part of M-Bcr recombined within, or immediately adjacent to, Alu elements at the additional sites in all five complex BCR-ABL rearrangements that have been examined so far. This is a new finding which suggests that Alu sequences have an affinity for the BCR-ABL recombination process in complex rearrangements, and provides additional evidence for the association of these elements with somatic rearrangements which cause human leukaemia. We further show that sequence motifs similar to IgH switch pentamers and consensus binding sites of the lymphoid-associated Translin protein are present on one or more participating strands at 3'M-Bcr recombination sites. Motifs similar to Translin-binding sites were also identified within the Alu consensus. Expressed sequences mapped close to the breakpoint sites on other chromosomes in three of the five cases examined.

The photoautotrophic cyanobacterium Synechocystis sp. PCC 6803 is a widely used model in genomic research and was the first photosynthetic organism to have its entire genome sequenced. Here, we report the genome sequence for two glucose-tolerant laboratory 'wild-type' strains, GT-O1 and GT-O2, in use at the University of Otago. Using high-throughput genome sequencing techniques and subsequent Sanger sequencing of detected variants, we have identified ten de novo mutations in the two strains, of which six are unique to GT-O2 cells. The presence of these unique mutations highlights the need to know the genomic background of the parent strain when constructing mutants in Synechocystis sp. PCC 6803 strains.

Melanoma is a very aggressive neoplasm with a propensity to undergo progression and invasion early in its evolution. The molecular pathways underpinning invasion in melanoma are now just beginning to be elucidated, but a clear understanding of the transition from non-invasive to invasive melanoma cells remains elusive. Microphthalmia-associated transcription factor (MITF), is thought to be a central player in melanoma biology, and it controls many aspects of the phenotypic expression of the melanocytic lineage. However, recently the paired box transcription factor PAX3 was shown to transcriptionally activate POU3F2/BRN2, leading to direct repression of MITF expression. Here we present a theory to explain melanoma phenotype switching and discuss the predictions that this theory makes. One prediction is that independent and opposing roles for MITF and PAX3 in melanoma would be expected, and we present empirical evidence supporting this: in melanoma tissues PAX3 expression occurs independently of MITF, and PAX3 does not play a key role in melanoma cell proliferation. Furthermore, we show that knockdown of PAX3 inhibits cell migration in a group of “lower MITF” melanoma cell lines, while knockdown of MITF promotes cell migration in a complementary “higher MITF” group of melanoma cell lines. Moreover, the morphological effects of knocking down PAX3 versus MITF in melanoma cells were found to differ. While these data support the notion of independent roles for MITF and PAX3, additional experiments are required to provide robust examination of the proposed genetic switch theory. Only upon clear delineation of the mechanisms associated with progression and invasion of melanoma cells will successful treatments for invasive melanoma be developed.

GLI pathogenesis-related 1 (GLIPR1) was previously identified as an epigenetically regulated tumor suppressor in prostate cancer and, conversely, an oncoprotein in glioma. More recently, GLIPR1 was shown to be differentially expressed in other cancers including ovarian, acute myeloid leukemia, and Wilms’ tumor. Here we investigated GLIPR1 expression in metastatic melanoma cell lines and tissue. GLIPR1 was variably expressed in metastatic melanoma cells, and transcript levels correlated with degree of GLIPR1 promoter methylation in vitro. Elevated GLIPR1 levels were correlated with increased invasive potential, and siRNA-mediated knockdown of GLIPR1 expression resulted in reduced cell migration and proliferation in vitro. Immunohistochemical studies of melanoma tissue microarrays showed moderate to high staining for GLIPR1 in 50% of specimens analyzed. GLIPR1 staining was observed in normal skin in merocrine sweat glands, sebaceous glands, and hair follicles within the dermis.

No abstract