Essential Functions of the Histone Demethylase Lid

Drosophila Little imaginal discs (Lid) is a recently described member of the JmjC domain class of histone demethylases that specifically targets trimethylated histone H3 lysine 4 (H3K4me3). To understand its biological function, we have utilized a series of Lid deletions and point mutations to assess the role that each domain plays in histone demethylation, in animal viability, and in cell growth mediated by the transcription factor dMyc. Strikingly, we find that lid mutants are rescued to adulthood by either wildtype or enzymatically inactive Lid expressed under the control of its endogenous promoter, demonstrating that Lid's demethylase activity is not essential for development. In contrast, ubiquitous expression of UAS-Lid transgenes lacking its JmjN, C-terminal PHD domain, and C5HC2 zinc finger were unable to rescue lid homozygous mutants, indicating that these domains carry out Lid's essential developmental functions. Although Lid-dependent demethylase activity is not essential, dynamic removal of H3K4me3 may still be an important component of development, as we have observed a genetic interaction between lid and another H3K4me3 demethylase, dKDM2. We also show that Lid's essential C-terminal PHD finger binds specifically to di- and trimethylated H3K4 and that this activity is required for Lid to function in dMyc-induced cell growth. Taken together, our findings highlight the importance of Lid function in the regulated removal and recognition of H3K4me3 during development

Principles of genetic circuit design

Cells navigate environments, communicate and build complex patterns by initiating gene expression in response to specific signals. Engineers seek to harness this capability to program cells to perform tasks or create chemicals and materials that match the complexity seen in nature. This Review describes new tools that aid the construction of genetic circuits. Circuit dynamics can be influenced by the choice of regulators and changed with expression 'tuning knobs'. We collate the failure modes encountered when assembling circuits, quantify their impact on performance and review mitigation efforts. Finally, we discuss the constraints that arise from circuits having to operate within a living cell. Collectively, better tools, well-characterized parts and a comprehensive understanding of how to compose circuits are leading to a breakthrough in the ability to program living cells for advanced applications, from living therapeutics to the atomic manufacturing of functional materials.National Institute of General Medical Sciences (U.S.) (Grant P50 GM098792)National Institute of General Medical Sciences (U.S.) (Grant R01 GM095765)National Science Foundation (U.S.). Synthetic Biology Engineering Research Center (EEC0540879)Life Technologies, Inc. (A114510)National Science Foundation (U.S.). Graduate Research FellowshipUnited States. Office of Naval Research. Multidisciplinary University Research Initiative (Grant 4500000552

Trans-ethnic genome-wide association study of colorectal cancer identifies a new susceptibility locus in VTI1A

The genetic basis of sporadic colorectal cancer (CRC) is not well explained by known risk polymorphisms. Here we perform a meta-analysis of two genome-wide association studies in 2,627 cases and 3,797 controls of Japanese ancestry and 1,894 cases and 4,703 controls of African ancestry, to identify genetic variants that contribute to CRC susceptibility. We replicate genome-wide statistically significant associations (P<5 × 10(-8)) in 16,823 cases and 18,211 controls of European ancestry. This study reveals a new pan-ethnic CRC risk locus at 10q25 (rs12241008, intronic to VTI1A; P=1.4 × 10(-9)), providing additional insight into the aetiology of CRC and highlighting the value of association mapping in diverse populations

A genome-wide association study for colorectal cancer identifies a risk locus in 14q23.1

Over 50 loci associated with colorectal cancer (CRC) have been uncovered by genome-wide association studies (GWAS). Identifying additional loci has the potential to help elucidate aspects of the underlying biological processes leading to better understanding of the pathogenesis of the disease. We re-evaluated a GWAS by excluding controls that have family history of CRC or personal history of colorectal polyps, as we hypothesized that their inclusion reduces power to detect associations. This is supported empirically and through simulations. Two-phase GWAS analysis was performed in a total of 16,517 cases and 14,487 controls. We identified rs17094983, a SNP associated with risk of CRC [p = 2.5 × 10(-10); odds ratio estimated by re-including all controls (OR) = 0.87, 95% confidence interval (CI) 0.83-0.91; minor allele frequency (MAF) = 13%]. Results were replicated in samples of African descent (1894 cases and 4703 controls; p = 0.01; OR = 0.86, 95% CI 0.77-0.97; MAF = 16 %). Gene expression data in 195 colon adenocarcinomas and 59 normal colon tissues from two different studies revealed that this locus has genotypes that are associated with RTN1 (Reticulon 1) expression (p = 0.001), a protein-coding gene involved in survival and proliferation of cancer cells which is highly expressed in normal colon tissues but has significantly reduced expression in tumor cells (p = 1.3 × 10(-8))

Connexins in the early development of the African clawed frog Xenopus laevis (Amphibia): The role of the connexin43 carboxyl terminal tail in the establishment of the dorso-ventral axis

Connexins are a family of related proteins identified in vertebrate forming gap junctions, which mediate cell-to-cell communication in early embryos, with an important role in establishing embryonic asymmetry and ‘communication compartments’. By in situ hybridization, immunocytochemistry, reverse transcriptase PCR (RT-PCR) and western blotting we show that a Cx43-like molecule is present in oocytes and embryos of the African clawed frog Xenopus laevis, with specific localization in the animal-vegetal axis. This specific distribution is suggestive for an important role for this protein in the establishment of the dorso-ventral axis. Antisense RNA and antibodies directed against rat carboxyl terminal tail of the Cx43 (CT-Cx43) and injected in 1-cell stage Xenopus embryos, induced pronounced alterations in nervous system development, with a severe ventralization phenotype. Coherently, the overexpression of CT-Cx43 produced a dorsalization of the embryos. In antisense treated embryos, the expression of the beta-catenin gene is eliminated from the Nieuwkoop center, the pattern expression of the Chordin, Xnot and Xbra is modified, with no effect in expression of the Goosecoid gene. In CT-Cx43 mRNA treated embryos the pattern of expression of the beta-catenin, Chordin, Goosecoid, Xnot and engrailed-2 genes is modified. The expression of beta-catenin is increased in the Nieuwkoop center, the expression pattern of Chordin and Goosecoid is expanded to the posterior neural plate and engrailed-2 presents ectopic expression in the ventral region. Taken together our data suggest a role for CT-Cx43 as a maternal determinant with a critical function in the formation of the dorso-ventral axis in Xenopus laevis. The Cx43 may be one of the earliest markers of the dorso-ventral axis in these embryos and could possibly be acting through regionalization of factors responsible for the establishment of this axis

Regulation of gap junctions by protein phosphorylation

Gap junctions are constituted by intercellular channels and provide a pathway for transfer of ions and small molecules between adjacent cells of most tissues. The degree of intercellular coupling mediated by gap junctions depends on the number of gap junction channels and their activity may be a function of the state of phosphorylation of connexins, the structural subunit of gap junction channels. Protein phosphorylation has been proposed to control intercellular gap junctional communication at several steps from gene expression to protein degradation, including translational and post-translational modification of connexins (i.e., phosphorylation of the assembled channel acting as a gating mechanism) and assembly into and removal from the plasma membrane. Several connexins contain sites for phosphorylation for more than one protein kinase. These consensus sites vary between connexins and have been preferentially identified in the C-terminus. Changes in intercellular communication mediated by protein phosphorylation are believed to control various physiological tissue and cell functions as well as to be altered under pathological conditions