It is shown that long-term potentiation (LTP) is the cellular basis of memory formation. However, since all but small fraction of memories are forgotten, LTP has been further divided into early LTP (e-LTP), the mechanism by which short-term memories are formed, and a more stable late LTP (L-LTP), by which long-term memories are formed. Remarkably, it has been shown that an e-LTP can be stabilized if it is preceded or followed by heterosynaptic L-LTP. According to Synaptic Tagging and Capture (STC) hypothesis, e-LTP is stabilized by capturing proteins that are made by L-LTP induction. The model proposes that this mechanism underlies the formation of late associative memory, where the stability of a memory is not only defined by the stimuli that induce the change but also by events happening before and after these stimuli. As such, the model explicitly predicts that a short-term memory can be stabilized by inducing heterosynaptic L-LTP. In this grant, I will put this hypothesis into test. Specifically, I will test two explicit predictions of STC model: 1) A naturally formed short-term memory can be stabilized by induction of heterosynaptic L-LTP. 2) This stabilization is caused by the protein synthesis feature of L-LTP. To do this, using optogenetics, I will engineer a short-term memory in auditory fear circuit, in which an animal transiently associates a foot shock to a tone. Subsequently, I will examine if optogenetic delivery of L-LTP to the visual inputs converging on the same population of neurons in the amygdala will stabilize the short-term tone fear memory. To be able to engineer natural memory by manipulating synaptic plasticity I will develop two systems: 1) A two-color optical activation system which permits selective manipulation of distinct neuronal populations with precise temporal and spatial resolution; 2) An inducible and activity-dependent expression system by which those neurons that are activated by a natural stimulus will be optically tagged.

Synthetic biology aims at re-engineering organisms for practical applications by designing novel biomolecular components, networks, and pathways. The field is expected to lead to cheaper drugs, sustainable fuel production, efficient diagnosis and targeted therapies for diseases. However, a major obstacle to achieve these goals is our limited ability to rationally design biomolecular structure and function. By contrast, the field of DNA nanotechnology has so far demonstrated an unprecedented ability to design and self-assemble well-defined molecular shapes, although the production method of thermal annealing is not compatible with cells. We have recently demonstrated a breakthrough method, called RNA origami, which allows the design of RNA molecules that fold into well-defined nanoscale shapes during their synthesis by an RNA polymerase. In this proposal I aim at extending this technology to produce RNA-protein nanostructures and at demonstrating their application in synthetic biology. My primary scientific hypothesis is that understanding the folding process during synthesis will help us to design nanostructures that can be produced in cells. I will design a general RNA-protein architecture that is compatible with folding during synthesis. I will investigate folding kinetics to be able to design and program the dynamical folding process. Based on this, RNA-protein nanostructures will be designed, expressed in cells, and verified, for the formation of the desired shapes. We will develop new functionalities by both rational design and selection approaches with the aim of obtaining multivalent-binding and switching properties. Finally, the functional RNA-protein nanostructures will be applied in proof-of-concept experiments to demonstrate efficient, multivalent targeting of subcellular structures, biosensing of a variety of intracellular analytes, metabolic channeling of biosynthesis pathways, and complex control of transcriptional networks.

Atomically thin semiconductors are emerging as an important class of quantum materials that provide groundbreaking functionalities in device architectures. In particular, tailoring quantum degrees of freedom associated with charge, spin and orbital quantum numbers, as well as twist angle, could enable novel electronic, spintronic, valleytronic and twistronic applications. These fascinating properties are all contained in the quantum mechanical wavefunctions associated with the charge carrying electrons and holes of the semiconductors. Here, I will prepare heterostructures of two-dimensional (2D) transition metal dichalcogenide semiconductors and use the strong many-body interactions in the materials to generate condensates of electron-hole pair excitations. The many-body wavefunctions of these so-called exciton condensates will be visualised for the first time using advanced photoemission spectroscopies that provide complementary access to the energy-, momentum-, time- and length-scales of the excitations. I hypothesise that this fundamental level of control of the underlying quantum mechanisms of the semiconductors will ultimately enable highly specific quantum engineering of 2D optoelectronic devices. I will combine my expertise on non-equilibrium femtosecond dynamics of 2D semiconductors with the capabilities of my host group at Aarhus University, Denmark, in order to gain access to multiple photoemission spectroscopy experiments with nanoscale spatial resolution and femtosecond time-resolution, as well as 2D material fabrication facilities. These new skills and networking opportunities will ultimately enable me to obtain a permanent academic position.