Prof. Dr. Henrik Mouritsen
Neurosensorics/Animal Navigation group
Carl von Ossietzky Universität Oldenburg
Phone: +49 (0) 441 798 3081 or 3095
magnetic field generation, light & radiofrequency setup/measurements; data science & statistical analysis
|Brain research|| |
neuronal tract tracing, immunohistochemistry, neuron activity markers
|Retina research|| |
cut loading, dye injection, patch clamp, two-photon calcium imaging
expression and purification of cryptochrome proteins, isotopic substitution of recombinant proteins, affinity chromatography methods, SDS-PAGE, Western Blot, FRET, yeast-two-hybrid assays, PCR
We are investigating the migratory orientation behaviour of two local, night-migratory songbird species, the European Robin and the Eurasian Blackcap. Behavioural experiments are conducted after sunset in our worldwide unique non-magnetic houses, using modified Emlen funnels as an experimental set-up, to test which migratory direction the birds would like to take.
We focus on the birds’ magnetic compass, by testing them in different magnetic field conditions, which we generate with our magnetic coil systems. By applying different treatments to investigate which conditions do or do not allow the bird to orient, we seek to gain a better understanding of the avian magnetic compass.
Such conditions can be for example:
1) The composition of the light spectrum or monochromatic light conditions, giving insights into what the spectral prerequisites for the magnetic compass mechanism are.
2) The disruption of the proposed quantum chemical magnetoreception mechanism by radiofrequency fields, generating information about the organic nature of the involved molecules.
All test treatments can be adapted for the specific research questions and then combined with our behavioural assay. Good data management, data processing and statistical analysis of our double-blinded experiments, are crucial at the end of each migratory season.
We investigate the neurobiological basis of magnetoreception and navigation in night-migratory songbirds. To shed light on where and how navigational information is processed in the avian brain, we use techniques such as neuronal tract tracing, immunohistochemistry, and neuron activity markers.
For neuronal tract tracing we are working with conventional tracers such as cholera toxin subunit B, biotin and DiI, but also with adeno associated viruses (AAVs) which express fluorescent molecules for example eGFP and mRuby.
To further investigate those neuronal tract tracings and to characterize the brain of night-migratory songbirds, we are performing immunohistochemistry with substrates as well as fluorescent stainings.
To be able to find out if navigation especially magnetoreception is performed in a specific brain region, we use neuron activity markers against immediate early genes which are expressed after a stimulus occurred.
After neuronal tract tracing, we analyze our data qualitatively using expression patterns and special neuronal features known from other avian species but also quantitively by measuring density and comparing activity patterns between conditions. For purposes like this, we are working with imaging software like Fiji by ImageJ, adobe photoshop and illustrator but also calculating programs such as Matlab and R.
We are working on diverse aspects of vertebrate retina:
1) We load tracers and various substances (for example Neurobiotin) into retinal neuron cells and track the tracer flowing. This will show us the permeability of gap junction channels between retinal neurons. Through this experiment, we could potentially seek a way to deliver health signals through retinal gap junctions as a therapeutic avenue for retinal degeneration diseases;
2) To investigate the circuitry and functional role of retinal interneurons and horizontal cells, we use dye injection to visualize the morphology of horizontal cells in mice (and bird) retina, reconstruct retinal neuron cells and look for the difference in dorsal, nasal, ventral and temporal areas. Also we study the difference of horizontal cell receptive field in distinct retinal areas;
3) To investigate the circuitry for light-dependent magnetoreception in the bird retina, we use electrophysiological techniques such as patch clamp and two-photon calcium imaging to elucidate the synaptic connections and retinal signaling pathways from putatively magnetosensitive photoreceptors to thalamus-projecting ganglion cells in migratory birds.
Our main focus is how Cryptochrome 4 (Cry4) responds to magnetic fields via a radical pair mechanism and how Cry4 interacts with other proteins for signal transduction. We combine molecular and biochemical methods, spectroscopic techniques, and live cell imaging to gain important insight into Cry4 magnetic sensing and signaling functions. As part of our toolset, recombinant protein expression and purification methods allow a huge amount of functional Cry4 protein production for various spectroscopic measurements. Using the established protein production pipeline, we routinely express Cry4 proteins from different animal species. One of the proteins is Cry4 protein from the European robin. Together with collaborators in Oxford, we demonstrated the magnetic sensitivity of the Cry4 protein, which was published as a cover story of Nature Journal (Xu et al., 2021). At the same time, we house the methods of Förster resonance energy transfer and fluorescence lifetime imaging microscopy for CRY4 protein interaction studies. We are constantly developing new methods depending on the research questions.