Functional redundancy between RAP1 isoforms in murine platelet production and function

RAP GTPases, important regulators of cellular adhesion, are abundant signaling molecules in the platelet/megakaryocytic lineage. However, mice lacking the predominant isoform, RAP1B, display a partial platelet integrin activation defect and have a normal platelet count, suggesting the existence of a RAP1-independent pathway to integrin activation in platelets and a negligible role for RAP GTPases in megakaryocyte biology. To determine the importance of individual RAP isoforms on platelet production and on platelet activation at sites of mechanical injury or vascular leakage, we conditionally deleted Rap1a and/or Rap1b in the megakaryocytic lineage (mKO). Interestingly, Rap1a/b-mKO mice displayed a marked macrothrombocytopenia due to impaired pro- platelet formation by megakaryocytes. In platelets, RAP isoforms had both redundant and isoform-ˇspecific functions. Deletion of RAP1B, but not RAP1A, significantly reduced α- granule secretion and activation of the cytoskeleton regulator RAC1. Both isoforms significantly contributed to thromboxane A2 generation and the inside-out activation of platelet integrins. Combined deficiency of RAP1A and RAP1B markedly impaired platelet aggregation, spreading and clot retraction. Consistently, thrombus formation in physiological flow conditions was abolished in Rap1a/b-mKO, but not Rap1a-mKO or Rap1b-mKO platelets. Rap1a/b-mKO mice were strongly protected from experimental thrombosis and exhibited a severe defect in hemostasis after mechanical injury. Surprisingly, Rap1a/b-mKO platelets were indistinguishable from controls in their ability to prevent blood-lymphatic mixing during development and hemorrhage at sites of inflammation. In summary, our studies demonstrate an essential role for RAP1 signaling in platelet integrin activation and a critical role in platelet production. While important for hemostatic/thrombotic plug formation, platelet RAP1 signaling is dispensable for vascular integrity during development and inflammation

The Na(+)/Ca(2+) exchanger NCKX4 governs termination and adaptation of the mammalian olfactory response

Sensory perception requires accurate encoding of stimulus information by sensory receptor cells. We identified NCKX4, a potassium-dependent Na(+)/Ca(2+) exchanger, as being necessary for rapid response termination and proper adaptation of vertebrate olfactory sensory neurons (OSNs). Nckx4(-/-) (also known as Slc24a4) mouse OSNs displayed substantially prolonged responses and stronger adaptation. Single-cell electrophysiological analyses revealed that the majority of Na(+)-dependent Ca(2+) exchange in OSNs relevant to sensory transduction is a result of NCKX4 and that Nckx4(-/-) mouse OSNs are deficient in encoding action potentials on repeated stimulation. Olfactory-specific Nckx4(-/-) mice had lower body weights and a reduced ability to locate an odorous source. These results establish the role of NCKX4 in shaping olfactory responses and suggest that rapid response termination and proper adaptation of peripheral sensory receptor cells tune the sensory system for optimal perception

Organic carbon content and carbon isotope variations across the Permo-Triassic boundary in the Gartnerkofel-1 borehole, Carnic Alps, Austria

The Gartnerkofel borehole is one of the most thoroughly studied and described Permo-Triassic sections in the world. Detailed bulk organic carbon isotope studies show a negative base shift from − 24‰ to − 28‰ in the Latest Permian which latter value persists into the Earliest Triassic after which it decreases slightly to − 26‰. Two strongly negative peaks of > − 38‰ in the Latest Permian and a lesser peak of − 31‰ in the Early Triassic are too negative to be due to a greater proportion of more negative organic matter and must be due to very negative methane effects. The overall change to more negative values across the Bulla/Tesero boundary fits the relative rise in sea level for this transition based on the facies changes. A positive shift in organic carbon isotope values at the Late Permian Event Horizon may be due to an increase in land-derived organic detritus at this level—a feature shown by all Tethyan Permo-Triassic boundary sections though these other sections do not have the same values. Carbonate carbon isotope trends are similar in all sections dropping by 2–3 units across the Permo-Triassic boundary. Gartnerkofel carbonate oxygen values are surprisingly, considering the ubiquitous dolomitization, compatible with values elsewhere and indicate reasonable tropical temperatures of 60 °C in the Latest Permian sabkhas to 20–40 °C in the overlying marine transition beds. Increased land-derived input at the Late Permian Event Horizon may be due to offshore transport by tsunamis whose deposits have been recognized in India at this level

Microstructure, growth banding and age determination of a primnoid gorgonian skeleton (Octocorallia) from the late Younger Dryas to earliest Holocene of the Bay of Biscay

A fossil primnoid gorgonian skeleton (Octocorallia) was recovered on the eastern Galician Massif in the Bay of Biscay (NE Atlantic) from 720 m water depth. The skeleton shows a growth banding of alternating Mg–calcitic and organic (gorgonin) increments in the inner part, surrounded by a ring of massive fibrous calcite. Three calcite-dominated cycles, bounded by thick organic layers, consist of five light-dark couplets of calcite and gorgonin. Two AMS-14C datings of the fossil skeleton give ages of 10,880 and 10,820 ± 45 14C years before present (BP). We arrive at a calibrated age range of 11,829–10,072 cal. years BP (two σ), which comprises the late Younger Dryas to the earliest part of the Holocene. The cyclic calcitic–organic growth banding may be controlled by a constant rate of calcite secretion with a fluctuating rate of gorgonin production, possibly related to productivity cycles. The skeletal fabric change of alternating calcitic–organic increments to massive fibrous calcite may be the result of hydrographic changes during the deglaciation as reflected by preliminary stable isotope data. If this hypothesis proves to be correct, primnoid gorgonians are able to match with varying hydrodynamic conditions by changing their biomineralisation mode

The genome of Ectocarpus subulatus – a highly stress-tolerant brown alga

International audienceBrown algae are multicellular photosynthetic stramenopiles that colonize marine rocky shores worldwide. Ectocarpus sp. Ec32 has been established as a genomic model for brown algae. Here we present the genome and metabolic network of the closely related species, Ectocarpus subulatus Kützing, which is characterized by high abiotic stress tolerance. Since their separation, both strains show new traces of viral sequences and the activity of large retrotransposons, which may also be related to the expansion of a family of chlorophyll-binding proteins. Further features suspected to contribute to stress tolerance include an expanded family of heat shock proteins, the reduction of genes involved in the production of halogenated defence compounds, and the presence of fewer cell wall polysaccharide-modifying enzymes. Overall, E. subulatus has mainly lost members of gene families down-regulated in low salinities, and conserved those that were up-regulated in the same condition. However, 96% of genes that differed between the two examined Ectocarpus species, as well as all genes under positive selection, were found to encode proteins of unknown function. This underlines the uniqueness of brown algal stress tolerance mechanisms as well as the significance of establishing E. subulatus as a comparative model for future functional studies

Red pigment production by Penicillium purpurogenum GH2 is influenced by pH and temperature*

The combined effects of pH and temperature on red pigment production and fungal morphology were evaluated in a submerged culture of Penicillium purpurogenum GH2, using Czapek-Dox media with D-xylose as a carbon source. An experimental design with a factorial fix was used: three pH values (5, 7, and 9) and two temperature levels (24 and 34 °C) were evaluated. The highest production of red pigment (2.46 g/L) was reached with a pH value of 5 and a temperature of 24 °C. Biomass and red pigment production were not directly associated. This study demonstrates that P. purpurogenum GH2 produces a pigment of potential interest to the food industry. It also shows the feasibility of producing and obtaining natural water-soluble pigments for potential use in food industries. A strong combined effect (p<0.05) of pH and temperature was associated with maximal red pigment production (2.46 g/L)