Regional trends and preliminary results on the local expansion rate in the invasive garden ant, <Emphasis Type="Italic">Lasius neglectus</Emphasis> (Hymenoptera,Formicidae)

The expansion process of the invasive garden ant, Lasius neglectus in Europe and Asia is described in terms of: a) local expansion through colony growing measured on four supercolonies (Seva, Debrecen, Buda Castle and Budatétény) from two distant and climatically different countries (Spain, Hungary), and b) regional expansion, using data from all published and several new non-native localities. Short, local distance processes (few meters to 89 m year-¹), as colony budding, are two to five orders of magnitude smaller than long regional distances (ten km to >1000 km). This suggests direct human intervention in the invasive spread. The regional trend also shows that the invasive garden ant has been quickly and steadily increasing the number of non native localities (77) and countries (14) it has reached during the last 30 years. Received 2 January 2006; revised 17 May 2007; accepted 1 June 2007.     

Isolating and expanding endothelial progenitor cells from peripheral blood on peptide-functionalized polystyrene surfaces

The expansion of human peripheral blood endothelial progenitor cells to obtain therapeutically relevant endothelial colony-forming cells (ECFCs) has been commonly performed on xeno-derived extracellular matrix proteins. For cellular therapy applications, xeno-free culture conditions are desirable to improve product safety and reduce process variability. We have previously described a novel fluorophore-tagged RGD peptide (RGD-TAMRA) that enhanced the adhesion of mature endothelial cells in vitro. To investigate whether this peptide can replace animal-derived extracellular matrix proteins in the isolation and expansion of ECFCs, peripheral blood mononuclear cells from 22 healthy adult donors were seeded on RGD-TAMRA-modified polystyrene culture surfaces. Endothelial colony formation was significantly enhanced on RGD-TAMRA-modified surfaces compared to the unmodified control. No phenotypic differences were detected between ECFCs obtained on RGD-TAMRA compared to ECFCs obtained on rat-tail collagen-coated surfaces. Compared with collagen-coated surfaces and unmodified surfaces, RGD-TAMRA surfaces promoted ECFC adhesion, cell spreading, and clonal expansion. This study presents a platform that allows for a comprehensive in vitro evaluation of peptide-based biofunctionalization as a promising avenue for ex vivo ECFC expansion.     

Developmental defects and seedling lethality in apyrase <Emphasis Type="Italic">AtAPY1</Emphasis> and <Emphasis Type="Italic">AtAPY2</Emphasis> double knockout mutants

Previously it was shown that the Arabidopsis apyrase genes AtAPY1 and AtAPY2 are crucial for male fertility because mutant pollen (apy1-1; apy2-1) with T-DNA insertions in both genes could not germinate (Steinebrunner et al. (2003) Plant Physiol. 131: 1638–1647). In this study, pollen germination was restored and apyrase T-DNA double knockouts (DKO) apy1-1/apy1-1; apy2-1/apy2-1 were generated by complementation with AtAPY2 under the control of a pollen-specific promoter. The DKO phenotype displayed developmental defects including the lack of functional root and shoot meristems. In cotyledons, morphogenetic and patterning abnormalities were apparent, e.g., unlobed pavement cells and stomatal clusters. Another set of lines was created which carried either AtAPY1 or AtAPY2 under a dexamethasone-(DEX)-inducible promoter as an additional transgene to the pollen-specific gene construct. Application of DEX did not reverse the DKO phenotype to wild-type, but some inducible lines exhibited less severe defects even in the absence of the inducer, probably due to some background expression. However, even these DKO mutants were seedling-lethal and shared other defects regarding cell division, cell expansion and stomatal patterning. Taken together, the defects in the DKO mutants demonstrate that AtAPY1 and AtAPY2 are essential for normal plant development.     

Genetic drift during the spread phase of a biological invasion

Recent theoretical and experimental models have revealed the role played by evolution during species spread, and in particular have questioned the influence of genetic drift at range edges. By investigating the spread of an aquatic invader in patchy habitats, we quantified genetic drift and explored its consequences for genetic diversity and fitness. We examined the interplay of gene flow and genetic drift in 36 populations of the red swamp crayfish, Procambarus clarkii, in a relatively recently invaded wetland area (30 years, Brière, northwest France). Despite the small spatial scale of our study (15 km²), populations were highly structured according to the strong barrier of land surfaces and revealed a clear pattern of colonization through watercourses. Isolated populations exhibited small effective sizes and low dispersal rates that depended on water connectivity, suggesting that genetic drift dominated in the evolution of allele frequencies in these populations. We also observed a significant decrease in the genetic diversity of isolated populations over only a 2‐year period, but failed to demonstrate an associated fitness cost using fluctuating asymmetry. This study documents the possible strong influence of genetic drift during the spread of a species, and such findings provide critical insights into the current context of profound rearrangements in species distributions due to global change.     

Metal Ion-dependent Heavy Chain Transfer Activity of TSG-6 Mediates Assembly of the Cumulus-Oocyte Matrix

The matrix polysaccharide hyaluronan (HA) has a critical role in the expansion of the cumulus cell-oocyte complex (COC), a process that is necessary for ovulation and fertilization in most mammals. Hyaluronan is organized into a cross-linked network by the cooperative action of three proteins, inter-α-inhibitor (IαI), pentraxin-3, and TNF-stimulated gene-6 (TSG-6), driving the expansion of the COC and providing the cumulus matrix with its required viscoelastic properties. Although it is known that matrix stabilization involves the TSG-6-mediated transfer of IαI heavy chains (HCs) onto hyaluronan (to form covalent HC·HA complexes that are cross-linked by pentraxin-3) and that this occurs via the formation of covalent HC·TSG-6 intermediates, the underlying molecular mechanisms are not well understood. Here, we have determined the tertiary structure of the CUB module from human TSG-6, identifying a calcium ion-binding site and chelating glutamic acid residue that mediate the formation of HC·TSG-6. This occurs via an initial metal ion-dependent, non-covalent, interaction between TSG-6 and HCs that also requires the presence of an HC-associated magnesium ion. In addition, we have found that the well characterized hyaluronan-binding site in the TSG-6 Link module is not used for recognition during transfer of HCs onto HA. Analysis of TSG-6 mutants (with impaired transferase and/or hyaluronan-binding functions) revealed that although the TSG-6-mediated formation of HC·HA complexes is essential for the expansion of mouse COCs in vitro, the hyaluronan-binding function of TSG-6 does not play a major role in the stabilization of the murine cumulus matrix.