Evolutionary mechanisms shaping the genetic population structure of marine fishes; lessons from the European flounder (Platichthys flesus L.)

A number of evolutionary mechanisms have been suggested for generating low but significant genetic structuring among marine fish populations. We used nine microsatellite loci and recently developed methods in landscape genetics and coalescence-based estimation of historical gene flow and effective population sizes to assess temporal and spatial dynamics of the population structure in European flounder (Platichthys flesus L.). We collected 1062 flounders from 13 localities in the northeast Atlantic and Baltic Seas and found temporally stable and highly significant genetic differentiation among samples covering a large part of the species' range (global F(ST) = 0.024, P < 0.0001). In addition to historical processes, a number of contemporary acting evolutionary mechanisms were associated with genetic structuring. Physical forces, such as oceanographic and bathymetric barriers, were most likely related with the extreme isolation of the island population at the Faroe Islands. A sharp genetic break was associated with a change in life history from pelagic to benthic spawners in the Baltic Sea. Partial Mantel tests showed that geographical distance per se was not related with genetic structuring among Atlantic and western Baltic Sea samples. Alternative factors, such as dispersal potential and/or environmental gradients, could be important for generating genetic divergence in this region. The results show that the magnitude and scale of structuring generated by a specific mechanism depend critically on its interplay with other evolutionary mechanisms, highlighting the importance of investigating species with wide geographical and ecological distributions to increase our understanding of evolution in the marine environment.     

4-amino-5-aryl-6-arylethynylpyrimidines: structure-activity relationships of non-nucleoside adenosine kinase inhibitors

A series of non-nucleoside adenosine kinase (AK) inhibitors is reported. These inhibitors originated from the modification of 5-(3-bromophenyl)-7-(6-morpholin-4-ylpyridin-3-yl)pyrido[2,3-d]pyrimidin-4-ylamine (ABT-702). The identification of a linker that would approximate the spatial arrangement found between the pyrimidine ring and the aryl group at C(7) in ABT-702 was a key element in this modification. A search of potential linkers led to the discovery of an acetylene moiety as a suitable scaffold. It was hypothesized that the aryl acetylenes, ABT-702, and adenosine bound to the active site of AK (closed form) in a similar manner with respect to the orientation of the heterocyclic base. Although potent acetylene analogs were discovered based on this assumption, an X-ray crystal structure of 5-(4-dimethylaminophenyl)-6-(6-morpholin-4-ylpyridin-3-ylethynyl)pyrimidin-4-ylamine (16a) revealed a binding orientation contrary to adenosine. In addition, this compound bound tightly to a unique open conformation of AK. The structure-activity relationships and unique ligand orientation and protein conformation are discussed.     

Genetic variation and differentiation in captive and wild zebra finches (Taeniopygia guttata)

The zebra finch (Taeniopygia guttata) is a small Australian grassland songbird that has been domesticated over the past two centuries. Because it is easy to breed in captivity, it has become a widely used study organism, especially in behavioural research. Most work has been conducted on domesticated populations maintained at numerous laboratories in Europe and North America. However, little is known about the extent to which, during the process of domestication, captive populations have gone through bottlenecks in population size, leading to inbred and potentially genetically differentiated study populations. This is an important issue, because (i) behavioural studies on captive populations might suffer from artefacts arising from high levels of inbreeding or lack of genetic variation in such populations, and (ii) it may hamper the comparability of research findings. To address this issue, we genotyped 1000 zebra finches from 18 captive and two wild populations at 10 highly variable microsatellite loci. We found that all captive populations have lost some of the genetic variability present in the wild, but there is no evidence that they have gone through a severe bottleneck, as the average captive population still showed a mean of 11.7 alleles per locus, compared to a mean of 19.3 alleles/locus for wild zebra finches. We found significant differentiation between the captive populations (F(ST) = 0.062). Patterns of genetic similarity closely match geographical relationships, so the most pronounced differences occur between the three continents: Australia, North America, and Europe. By providing a tree of the genetic similarity of the different captive populations, we hope to contribute to a better understanding of variation in research findings obtained by different laboratories.     

Quantitative proteomic assessment of very early cellular signaling events

Technical limitations have prevented proteomic analyses of events occurring less than 30 s after signal initiation. We developed an automated, continuous quench-flow system allowing quantitative proteomic assessment of very early cellular signaling events (qPACE) with a time resolution of 1 s. Using this technique, we determined that autophosphorylation of the epidermal growth factor receptor occurs within 1 s after ligand stimulation and is followed rapidly by phosphorylation of the downstream signaling intermediates Src homologous and collagen-like protein and phospholipase C gamma 1.     

Identification of BARD1 splice-isoforms involved in human trophoblast invasion

The tumor suppressor protein BARD1, originally discovered as BRCA1-binding protein, acts in conjunction with BRCA1 as ubiquitin ligase. BARD1 and BRCA1 form a stable heterodimer and dimerization, which is required for most tumor suppressor functions attributed to BRCA1. In addition, BARD1 has BRCA1-independent functions in apoptosis, and a role in control of tissue homeostasis was suggested. However, cancer-associated mutations of BARD1 are rare; on the contrary, overexpression of truncated BARD1 was found in breast and ovarian cancer and correlated with poor prognosis. Here we report that human cytotrophoblasts, which show a strong similarity with cancer cells in respect of their invasive behavior and capacity of matrix metalloprotease production, overexpress isoforms of BARD1 derived from differential splicing. We demonstrate that expression of BARD1 and its isoforms is temporally and spatially regulated by human chorionic gonadotropin and by hypoxia, both factors known to regulate the invasive phase and proliferation of cytotrophoblasts. Interestingly, we found a subset of BARD1 isoforms secreted by cytotrophoblasts. BARD1 repression by siRNAs, mitigates the interference of cytotrophoblasts with cell adhesion of collagen matrix-dependent epithelial cells, suggesting a role of BARD1 isoforms in extracellular matrix remodelling and in cytotrophoblasts invasion.     

Long-term Patterns of Shifts between Clear and Turbid States in Lake Krankesjön and Lake Tåkern

During the past century, Lake Tåkern and Lake Krankesjön, southern Sweden, have shifted repeatedly between a state of clear water and abundant submerged vegetation, and a state of turbid water and sparse vegetation. Long-term empirical data on such apparently alternative stable state dynamics are valuable as complements to modeling and experiments, although the causal mechanisms behind shifts are often difficult to identify in hindsight. Here, we summarize previous studies and discuss possible mechanisms behind the shifts. The most detailed information comes from monitoring of two recent shifts, one in each lake. In the 1980s, L. Krankesjön shifted to clear water following an expansion of sago pondweed, Potamogeton pectinatus. Water clarity increased when the pondweed was replaced by characeans. Zooplankton biomass in summer declined and the concentration of total phosphorus (TP) was reduced to half the previous level. The fish community changed over several years, including an increasing recruitment of piscivorous perch (Perca fluviatilis). An opposite directed shift to turbid water occurred in Lake Tåkern in 1995, when biomass of phytoplankton increased in spring, at the expense of submerged vegetation. Consistent with the findings in L. Krankesjön, phyto- and zooplankton biomass increased and the average concentration of TP doubled. After the shift to clear water in L. Krankesjön, TP concentration has increased during the latest decade, supporting the idea that accumulation of nutrients may lead to a long-term destabilization of the clear water state. In L. Tåkern, data on TP are inconclusive, but organic nitrogen concentrations oscillated during a 25-year period of clear water. These observations indicate that intrinsic processes cause gradual or periodic changes in system stability, although we cannot exclude the possibility that external forces are also involved. During such phases of destabilization of the clear water state, even small disturbances could possibly trigger a shift, which may explain why causes behind shifts are hard to identify even when they occur during periods of extensive monitoring.     

Control of cell polarity and motility by the PtdIns(3,4,5)P3 phosphatase SHIP1

Proper neutrophil migration into inflammatory sites ensures host defense without tissue damage. Phosphoinositide 3-kinase (PI(3)K) and its lipid product phosphatidylinositol 3,4,5-trisphosphate (PtdIns(3,4,5)P(3)) regulate cell migration, but the role of PtdIns(3,4,5)P(3)-degrading enzymes in this process is poorly understood. Here, we show that Src homology 2 (SH2) domain-containing inositol-5-phosphatase 1 (SHIP1), a PtdIns(3,4,5)P(3) phosphatase, is a key regulator of neutrophil migration. Genetic inactivation of SHIP1 led to severe defects in neutrophil polarization and motility. In contrast, loss of the PtdIns(3,4,5)P(3) phosphatase PTEN had no impact on neutrophil chemotaxis. To study PtdIns(3,4,5)P(3) metabolism in living primary cells, we generated a novel transgenic mouse (AktPH-GFP Tg) expressing a bioprobe for PtdIns(3,4,5)P(3.) Time-lapse footage showed rapid, localized binding of AktPH-GFP to the leading edge membrane of chemotaxing ship1(+/+)AktPH-GFP Tg neutrophils, but only diffuse localization in ship1(-/-)AktPH-GFP Tg neutrophils. By directing where PtdIns(3,4,5)P(3) accumulates, SHIP1 governs the formation of the leading edge and polarization required for chemotaxis.