Under the pressure of human-induced climate change, it is essential to better understand the past natural climate variability. A broader global coverage of high-resolution palaeoclimatic proxy (indicator) data is urgently needed to improve climate projections and adaptation strategies to changing climate and environmental stress. Laminated lake sediments provide invaluable palaeoclimatic information with up to seasonal resolution. The IRONLAKE project aims to develop the innovative methodology of stable iron isotope measurements of laminated lake sediments as a novel proxy for past changes in temperature and wind. Only recently, first studies have hinted that variations in stable iron isotopes of marine and lake sediments reflect changing redox conditions in oceans and lakes, possibly linked to variations in past wind and/or temperature. This project aims to test the hypothesis of a redox-climate-relationship mirrored in iron isotopes. The project will be carried out on existing sediment cores from Lago Fagnano (Tierra del Fuego, Argentina) exhibiting characteristic iron-rich laminae that are most suitable for the approach. In a multidisciplinary perspective, a combination of ultrahigh-resolution micro-facies analysis by thin section microscopy and micro-X-ray-fluorescence elemental scanning will be applied to fully understand the general sedimentological and geochemical processes and, specifically, possible seasonal/climatic variations influencing the formation and deposition of iron-bearing minerals in the lake. The gained knowledge will then be linked with mineral-selective iron isotope measurements to infer the sensitivity of stable iron isotopes to capture climatic variations. The interdisciplinary perspective of this project is designed to advance the innovative field of iron isotope geochemistry and to provide a novel wind/temperature proxy to the palaeoclimate and climate modelling communities .
Cell division is a common process to all cell types in a multicellular organism. During mitosis, equal chromosome segregation in anaphase is regulated by an Aurora B phosphorylation gradient, centered at the midplane between the two chromosome sets. The gradient gives positional information that allows nuclear envelope reformation (NER) only when chromosomes are far enough from the kinase activity. Considering the 120μm human zygote and a 15μm fibroblast, how can the gradient scale with cell size over such wide range of sizes? To unravel the scaling mechanism, I will measure the biophysical parameters of this phosphorylation gradient using a FRET sensor and optogenetics to manipulate the gradient with fast spatiotemporal kinetics. I will address three key questions: i) Does the gradient sense cell size? ii) If so, how is size information used to scale the gradient? iii) How is gradient scaling translated into NER positioning? I will focus on three zebrafish cell systems with extreme sizes and dynamics: 1) embryonic cleavage divisions, where cell size halves with every cell division; 2) EVL cells, which are stretched quickly into flatter cell sizes, implying fast scaling dynamics; 3) asymmetric division in neuronal precursor cells, where the two sides of the spindle midzone must scale differently to generate daughters of different sizes. With this approach, I will generate unprecedented information on the regulation of anaphase chromosome separation in its natural context. This entry point in anaphase will provide a conceptual frame and a tool kit to address a more general problem: how do other mitotic machineries scale with cell size? A wider question for my long-term future research.
The rodent primary somatosensory cortex (S1) contains a malleable topographic map, in which cortical columns functionally represent individual facial whiskers. When all whiskers but two are trimmed, the cortical representations of the two spared whiskers partially fuse. This fusion is associated and possibly facilitated by an increase in NMDAR-mediated dendritic nonlinearities (plateau potentials) in L2/3 neurons, which are dependent on inputs from the higher-order posteromedial thalamic complex (POm). It has been shown that plateau potentials generated by these inputs can promote plasticity of sensory-related synaptic inputs. However, the spatiotemporal relationships between the plateau potential-generating POm and the sensory-related synaptic inputs on L2/3 neurons, and possible rearrangements therein during plasticity, are not understood. Recently developed genetically encoded glutamate indicators (GEGIs), which the fellow was involved in, have enabled the visualization of active excitatory inputs. Here, the fellow proposes a novel methodology (iMAC, Input Mapping of Active Connections), where she combines two state-of-the-art optogenetics and optophysiology tools. A presynaptic light-sensitive opsin will allow optical activation of ascending POm inputs, while a postsynaptic GEGI will allow the visualization, i.e. mapping of the activated synapses on L2/3 pyramidal neurons. First, the fellow will establish a proto-map of these higher-order thalamocortical excitatory inputs in an ex vivo preparation, followed by a proof of principle in vivo in the awake mouse. Second, the fellow will compare the POm-driven synaptic maps with those recruited by whisker sensory stimulation in vivo. Third, she will determine how these rearrange upon sensory deprivation. Altogether, this work will investigate the spatiotemporal relationships between POm and sensory-driven inputs onto L2/3 neurons and reveal possible rearrangements therein related to cortical map plasticity.
Request of financial support to cover the additional costs that researchers/staff members with disabilities face due to the increased costs of their mobility and/or to ensure necessary assistance by third persons or for adapting their work environment.