University of Dundee

About: University of Dundee is a education organization based out in Dundee, United Kingdom. It is known for research contribution in the topics: Population & Protein kinase A. The organization has 19258 authors who have published 39640 publications receiving 1919433 citations. The organization is also known as: Universitas Dundensis & Dundee University.

Integrating abundance and functional traits reveals new global hotspots of fish diversity

Abstract: Species richness has dominated our view of global biodiversity patterns for centuries(1,2). The dominance of this paradigm is reflected in the focus by ecologists and conservation managers on richness and associated occurrence-based measures for understanding drivers of broad-scale diversity patterns and as a biological basis for management(3,4). However, this is changing rapidly, as it is now recognized that not only the number of species but the species present, their phenotypes and the number of individuals of each species are critical in determining the nature and strength of the relationships between species diversity and a range of ecological functions (such as biomass production and nutrient cycling)(5). Integrating these measures should provide a more relevant representation of global biodiversity patterns in terms of ecological functions than that provided by simple species counts. Here we provide comparisons of a traditional global biodiversity distribution measure based on richness with metrics that incorporate species abundances and functional traits. We use data from standardized quantitative surveys of 2,473 marine reef fish species at 1,844 sites, spanning 133 degrees of latitude from all ocean basins, to identify new diversity hotspots in some temperate regions and the tropical eastern Pacific Ocean. These relate to high diversity of functional traits amongst individuals in the community (calculated using Rao's Q(6)), and differ from previously reported patterns in functional diversity and richness for terrestrial animals, which emphasize species-rich tropical regions only(7,8). There is a global trend for greater evenness in the number of individuals of each species, across the reef fish species observed at sites ('community evenness'), at higher latitudes. This contributes to the distribution of functional diversity hotspots and contrasts with well-known latitudinal gradients in richness(2,4). Our findings suggest that the contribution of species diversity to a range of ecosystem functions varies over large scales, and imply that in tropical regions, which have higher numbers of species, each species contributes proportionally less to community-level ecological processes on average than species in temperate regions. Metrics of ecological function usefully complement metrics of species diversity in conservation management, including when identifying planning priorities and when tracking changes to biodiversity values.

Efficient Differentiation of Hepatocytes from Human Embryonic Stem Cells Exhibiting Markers Recapitulating Liver Development In Vivo

Abstract: The potential to differentiate human embryonic stem cells (hESCs) in vitro to provide an unlimited source of human hepatocytes for use in biomedical research, drug discovery, and the treatment of liver diseases holds great promise. Here we describe a three-stage process for the efficient and reproducible differentiation of hESCs to hepatocytes by priming hESCs towards definitive endoderm with activin A and sodium butyrate prior to further differentiation to hepatocytes with dimethyl sulfoxide, followed by maturation with hepatocyte growth factor and oncostatin M. We have demonstrated that differentiation of hESCs in this process recapitulates liver development in vivo: following initial differentiation, hESCs transiently express characteristic markers of the primitive streak mesendoderm before turning to the markers of the definitive endoderm; with further differentiation, expression of hepatocyte progenitor cell markers and mature hepatocyte markers emerged sequentially. Furthermore, we have provided evidence that the hESC-derived hepatocytes are able to carry out a range of hepatocyte functions: storage of glycogen, and generation and secretion of plasma proteins. More importantly, the hESC-derived hepatocytes express several members of cytochrome P450 isozymes, and these P450 isozymes are capable of converting the substrates to metabolites and respond to the chemical stimulation. Our results have provided evidence that hESCs can be differentiated efficiently in vitro to functional hepatocytes, which may be useful as an in vitro system for toxicity screening in drug discovery.

Human mutsalpha recognizes damaged dna base pairs containing o6-methylguanine, o4-methylthymine, or the cisplatin-d(gpg) adduct

Abstract: Bacterial and mammalian mismatch repair systems have been implicated in the cellular response to certain types of DNA damage, and genetic defects in this pathway are known to confer resistance to the cytotoxic effects of DNA-methylating agents. Such observations suggest that in addition to their ability to recognize DNA base-pairing errors, members of the MutS family may also respond to genetic lesions produced by DNA damage. We show that the human mismatch recognition activity MutSalpha recognizes several types of DNA lesion including the 1,2-intrastrand d(GpG) crosslink produced by cis-diamminedichloroplatinum(II), as well as base pairs between O6-methylguanine and thymine or cytosine, or between O4-methylthymine and adenine. However, the protein fails to recognize 1,3-intrastrand adduct produced by trans-diamminedichloroplatinum(II) at a d(GpTpG) sequence. These observations imply direct involvement of the mismatch repair system in the cytotoxic effects of DNA-methylating agents and suggest that recognition of 1,2-intrastrand cis-diamminedichloroplatinum(II) adducts by MutSalpha may be involved in the cytotoxic action of this chemotherapeutic agent.

PTEN function: how normal cells control it and tumour cells lose it

Abstract: The PTEN (phosphatase and tensin homologue deleted on chromosome 10) tumour suppressor is a PI (phosphoinositide) 3-phosphatase that can inhibit cellular proliferation, survival and growth by inactivating PI 3-kinase-dependent signalling. It also suppresses cellular motility through mechanisms that may be partially independent of phosphatase activity. PTEN is one of the most commonly lost tumour suppressors in human cancer, and its deregulation is also implicated in several other diseases. Here we discuss recent developments in our understanding of how the cellular activity of PTEN is regulated, and the closely related question of how this activity is lost in tumours. Cellular PTEN function appears to be regulated by controlling both the expression of the enzyme and also its activity through mechanisms including oxidation and phosphorylation-based control of non-substrate membrane binding. Therefore mutation of PTEN in tumours disrupts not only the catalytic function of PTEN, but also its regulatory aspects. However, although mutation of PTEN is uncommon in many human tumour types, loss of PTEN expression seems to be more frequent. It is currently unclear how these tumours lose PTEN expression in the absence of mutation, and while some data implicate other potential tumour suppressors and oncogenes in this process, this area seems likely to be a key focus of future research.