Heparan sulfates and astrocytes

Just before the end 2016 we received the very welcome news that our study on the role of heparan sulfates got accepted for publication. Together with the lab of Alexander Dityatev we uncovered that heparan sulfates are required for the integrity of the axon initial segment of CA1 pyramidal cells. Their lack leads to reduced pyramidal cell excitability, reduced synaptic plasticity, altered theta oscillations in vivo and impaired context discrimination (link). The end of the year also saw the publication of a few other collaboration projects including the effect of dopamine on the Ca2+ signalling of hippocampal astrocytes (link) and the coupling properties of thalamic astrocytes (link) among others.

Please also see our selected Publications for more details.

New lab members and new lab picture

This is to welcome two new PhD students to the lab. Catia Domingos will be primarily working on molecular signals that acutely modify astrocyte morphology whereas Alberto Pauletti will look into the relationship between astrocyte morphology and astrocyte gap junction coupling.

And here is the group this autumn …

Claire is now Dr King

… and another welcome opportunity to celebrate. Claire passed the thesis oral examination yesterday. For the past years she has explored ‘The role of resting Ca2+ in astrocyte Ca2+ signalling’ and now she is Dr King. Well done and congratulations!

More things to celebrate

It is time for a new round of congratulations.

2015-09 11705454_1071374449556962_4064259067544279055_p The first two go to Eva and Björn who were MSc students in the lab for the past months working on astrocyte Ca2+ signaling and potassium clearance. ‘Were’ because their theses have been written, corrected and submitted and we are fairly certain we will have to address them by their appropriate title ‘Master’ soon.

The third goes to Michel. He successfully applied for a young investigator grant within the DFG SPP1757 on glial heterogeneity and now got some money for a student assistant for six months (research assistant job ad).

Well done everybody!

New group picture

Group picture 2015We finally managed to have our BBQ. A good opportunity to take a new group picture. From left to right Daniel, Christian, Anne, Michel, Kirsten, Steffi, Björn, Eva and Claire. A very casual picture. But still an improvement from last year’s “Orgelpfeifen”.


… to our collaborators here in Bonn in the lab of Christian Steinhäuser who uncovered a previously unknown contribution of astrocyte dysfunction to human epilepsy. Please see Publications for a link to the paper in Brain. And also congratulations to the lab of Colin Jackson at the ANU (Canberra, Australia) who successfully used ancestral protein reconstruction to design a novel optical arginine sensor. The paper is currently in press in Protein Science.

New lab members

Eva-Maria Schönhense (MSc. student), Björn Breithausen (MSc. student) and Anne Boehlen (PhD) have joined the lab to work on astrocyte Ca2+ signalling and potassium dynamics. Welcome aboard!

Optical sensor development at ANU

Funded by HFSP and DAAD we aANU sensor team + Michelre developing and testing optical sensors for neurotransmitters and other signalling molecules in the brain. Actually our collaborators in Austra (lab of Harald Janovjak, IST) and Australia (lab of Colin Jackson, ANU) are doing the hard work of designing the sensors while we test their suitability for imaging in intact tissue. To get a better understanding of what our colleagues at ANU are doing and to learn how to synthesize sensors ourselves here in Bonn we paid them a visit in November.

Needless to say it was quite pleasant to swap a northern hemisphere November for spring in Australia. More importantly, we now know how to produce the optical sensors ourselves. Also a first manuscript is nicely shaping up (sensor team ANU from left to right William Zhang, Jason Whitfield, Michel Herde (UKB), Colin Jackson, Ben Clifton).

PhD student stipend available

A PhD student stipend is available starting 2015. The goal is to reveal how rapid changes of astrocyte gap junction coupling modify hippocampal network function. More information can be found here. Application deadline is the 11th of January.

Two papers out

The structure of astrocytes is likely to shape the interaction between neurons and astrocytes in the brain. It is intuitive that astrocytes processes close to a synapse can more effectively modify synapse function than distant processes. Mike Stewart’s lab at Milton Keynes has now demonstrated in collaboration with us that astrocyte processes cover thin neuronal spines receiving excitatory input more than bigger spines, so called mushroom spines (Phil. Trans. R. Soc. B, link). This is of particular interest because thin spines are widely believed to represent spines at which long-term potentiation (LTP, the potential cellular mechanism of learning) has not occurred yet. It might suggest that these spines are particularly well protected from spill-in of neurotransmitter from neighboring synapses.

In a separate study we were wondering if morphology of whole astrocytes is heterogeneous within a brain region. Using fluorescence imaging in brain slices we could reveal that brain regions occupied by individual astrocytes can be oriented along principal cell dendrites (hippocampus, CA1 region). A subset of these cells had a morphology that could promote intracellular diffusion along along principal cell dendrites. Indeed astrocyte coupling, a key feature of astrocyte networks, was anisotropic and more pronounced along the same axis (Phil. Trans. R. Soc. B., link). These observations imply that astrocyte morphology determines spread of a diffusible signal within a gap junction coupled astrocyte network and can give it a directionality.

… and of course congratulations to all authors.