| 1. |
- Barber, D F, et al.
(författare)
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PTEN regulation, a novel function for the p85 subunit of phosphoinositide 3-kinase
- 2006
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Ingår i: Science Signaling. - 1937-9145. ; 362, s. 49-49
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Tidskriftsartikel (refereegranskat)abstract
- Timely regulation of phosphatidylinositol-3,4-bisphosphate [PI(3,4)P2] and phosphatidylinositol-3,4,5-trisphosphate [PI(3,4,5)P3] abundance in cells is essential for the control of cellular homeostasis. The concentrations of these lipids are low in quiescent cells but rapidly and transiently increase following growth factor receptor (GFR) stimulation, which triggers cellular metabolic changes, proliferation, survival, and motility. Class I(A) phosphatidylinositol 3-kinase (PI3K), which is composed of a p85 (regulatory) and p110 (catalytic) subunits, is the enzyme generating PI(3,4)P2 and PI(3,4,5)P3 following GFR stimulation. Although the steps in GFR-induced activation of PI3K , are relatively well known, the mechanisms for subsequent 3-polyphospho-PI down-regulation are less understood. Examination of frequent genetic alterations in human cancer showed that PTEN (phosphatase with tensin homology on chromosome 10) is the major enzyme that decreases PI(3,4)P2 and PI(3,4,5)P3 cell content. Nonetheless, interpretation of the complexity of PTEN regulation remains a matter of debate. The recent description of diminished PTEN activity in liver-conditional knockout mice lacking the p85alpha PI3K regulatory subunit reveals a previously unknown p85alpha-dependent negative-feedback pathway that controls PI(3,4)P2 and PI(3,4,5)P3 half-life by regulating PTEN.
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| 2. |
- van Noordwijk, AJ, et al.
(författare)
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A framework for the study of genetic variation in migratory behaviour
- 2006
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Ingår i: Journal of Ornithology. - : Springer Science and Business Media LLC. - 2193-7192 .- 2193-7206. ; 147:2, s. 221-233
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Evolutionary change results from selection acting on genetic variation. For migration to be successful, many different aspects of an animal's physiology and behaviour need to function in a co-coordinated way. Changes in one migratory trait are therefore likely to be accompanied by changes in other migratory and life-history traits. At present, we have some knowledge of the pressures that operate at the various stages of migration, but we know very little about the extent of genetic variation in various aspects of the migratory syndrome. As a consequence, our ability to predict which species is capable of what kind of evolutionary change, and at which rate, is limited. Here, we review how our evolutionary understanding of migration may benefit from taking a quantitative-genetic approach and present a framework for studying the causes of phenotypic variation. We review past research, that has mainly studied single migratory traits in captive birds, and discuss how this work could be extended to study genetic variation in the wild and to account for genetic correlations and correlated selection. In the future, reaction-norm approaches may become very important, as they allow the study of genetic and environmental effects on phenotypic expression within a single framework, as well as of their interactions. We advocate making more use of repeated measurements on single individuals to study the causes of among-individual variation in the wild, as they are easier to obtain than data on relatives and can provide valuable information for identifying and selecting traits. This approach will be particularly informative if it involves systematic testing of individuals under different environmental conditions. We propose extending this research agenda by using optimality models to predict levels of variation and covariation among traits and constraints. This may help us to select traits in which we might expect genetic variation, and to identify the most informative environmental axes. We also recommend an expansion of the passerine model, as this model does not apply to birds, like geese, where cultural transmission of spatio-temporal information is an important determinant of migration patterns and their variation.
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