Witnessing the birth of a tiny RNA at brain synapses
Proteins are the building blocks of all cells. They are made from messenger RNA (mRNA) molecules, which are copied from DNA in the nuclei of cells. All cells, including brain cells, called neurons, carry out their functions by carefully regulating the amount and kind of proteins they make. An important feature of neurons is their ability to communicate with one another at synapses, the points of contact between two cells. Synapses use proteins that are synthesized close-by to fuel communication and the formation of memories.
In neurons and other cells, protein synthesis is regulated by microRNAs, very small “non-coding” RNAs that bind, using complementary sequences, to mRNA and prevent the mRNA from being made into protein. microRNAs are made from larger precursor RNA molecules by several processing steps in the nucleus and cytoplasm. In individual cells, copy numbers of most microRNAs in single cells are relatively low in contrast to potential mRNA targets within individual cells where copy numbers can be up to 10,000 molecules. As such, the absolute number of potential mRNA targets within a cell for a single microRNA species could be very high (e.g. millions), raising the question of how a microRNA can effectively regulate a particular target mRNA.
In the February 10th issue of Science, the Schuman and Heckel labs, from the Max Planck Institute for Brain Research and Goethe University, respectively, show that neurons have solved the abundance problem by moving the site of microRNA maturation (or “birth”) away from the cytoplasm out to the dendrites, thin processes, which are closer to where synapses are. This puts the newly born microRNA into much smaller environment with fewer mRNA target options.
“We tested this hypothesis by using a clever design of a fluorescent molecular reporter, modelled after an immature microRNA”, Heckel says. “We filled neurons with this probe and then stimulated individual synapses. To our surprise, we could then see bright fluorescent spots at the stimulated synapses, showing us the birth of the microRNA. We then saw that the microRNA target was downregulated in the neighborhood of the dendrite where the microRNA was born”.
Schuman: “By moving the birthplace of the microRNA to the dendrites and synapses where it is closer to its targets, neurons have solved the microRNA-mRNA numbers game and gained a way for external events-resulting in the activation of synapses, to control the local expression of important brain molecules which is important for neuronal communication and also for memory formation”.
Publication: Sambandan, S., Akbalik, G., Kochen, L., Rinne, J. Kahlstatt, J., Glock, C. Tushev, G., Alvarez-Castelao, B., Heckel, A. and Schuman, E.M. (2017). Activity-dependent spatially-localized miRNA maturation in neuronal dendrites. Science 355: 634-637 Contact: Prof. Dr. Erin M. Schuman, Max Planck Institute for Brain Research, Max-von-Laue Str. 4, 60438 Frankfurt am Main, Germany, Email: email@example.com, T: +49 69 850033 1001 (Ms. Nicole Thomsen).
Frankfurt School documents: 13 bequests already
FRANKFURT.The Archive Centre of theJohann Christian Senckenberg University Library has been able to expand its collection of material on critical theory thanks to the bequest of philosopher Hermann Schweppenhäuser (1928-2015). Schweppenhäuser earned his doctorate in 1956 at the Institute for Social Research, which by that time had reopened. He was Theodor W. Adorno’s assistant up until 1961 and one of the most influential philosophers of the Frankfurt School. His bequest comprises about 75,000 pages and extensive unpublished archive material, which is accessible for research purposes at the Archive Centre.
Dr. Mathias Jehn, director of the Archive Centre, is very pleased: “This expands our collection on critical theory and the Frankfurt School tremendously. Our stock already includes, amongst others, the bequests of Max Horkheimer, Herbert Marcuse and Ludwig von Friedeburg as well as lifetime contributions from Jürgen Habermas and Oskar Negt.” The Institute for Social Research is also home to the Adorno archive and valuable historic stock from the 1950s and 1960s. Some of the Schweppenhäuser bequest has yet to be processed: “It’s so vast that this is going to take at least another twelve months”, says Jehn. But the bequest, which comprises extensive correspondence with international experts from the field of philosophy, partly unpublished scientific manuscripts as well as a few private documents, is now entirely in Frankfurt and was entrusted to the library by Gerhard Schweppenhäuser, the philosopher’s son.
In 1961, Hermann Schweppenhäuser, who was born in Frankfurt, moved to Lüneburg where he had been called to the newly established chair of philosophy at the College of Education. What was originally supposed to be an intermezzo became a lifetime post accompanied by an honorary professorship at Goethe University Frankfurt. Adorno evidently had other ideas too: in a card dated 14 October 1960 from Graz, which is also part of the bequest, he congratulated Schweppenhäuser “most sincerely” on his appointment in Lüneburg and added: “I hope that you will accept the post, which will certainly allow you to gain considerable experience, and this hope goes hand in hand with the hope that you will complete your post-doctoral degreequicklyand stay with us!”
Yet the critical theory of the Frankfurt School, which never was or is seen by most of the researchers involved as a closed circle with a uniform theory, developed in another direction and so Schweppenhäuser was not called to Goethe University Frankfurt. Habermas, who became Horkheimer’s successor in Frankfurt in 1964, retaliated several times in public against “being categorized uninterruptedly as a critical theorist”, although he had worshipped Adorno, as his biographer Stefan Müller-Doohm notes. Habermas developed his own independent idea of a societal communication theory “which regards itself not as transformation but entirely as an alternative to the critical theory of society”, says Müller-Doohm in an article in the FAZ newspaper (2016).
Whilst Habermas indeed shared Adorno’s and Horkheimer’s criticism of the one-sided technical and economic rationalization of modern culture and society, he chose a different perspective and focused his diagnosis on a “problematic primacy of economics over democratically legitimized politics, with which societies influence themselves”, says Müller-Doohm.
In the obituary he wrote for the weekly “jungle world” newspaper (2015), Roger Behrens is critical of the fact that Goethe University Frankfurt did not give Schweppenhäuser a chance: “Schweppenhäuser’s philosophy is the attempt to justify critical theory […] without falling into the trap and postulating on normativity, as did Jürgen Habermas and the academics who followed him […]. In contrast, Hermann Schweppenhäuser – a year older than Habermas incidentally – vigorously pursued the postulate of critical theory, in line with Horkheimer and Adorno, in line with Karl Marx and in line with Kant – as radical enlightenment [and] critique of power.”
Although not all documents have yet been viewed, the bequest makes it clear that Schweppenhäuser significantly shaped the discourse on Adorno and Benjamin through numerous essays, which enjoyed international acclaim and were partly translated. Schweppenhäuser formulated a version of critical theory “which is closer to the prime intention of Horkheimer and Adorno than the Frankfurt School with its communication theory as reformed by Habermas and his successors”, says his son Gerhard Schweppenhäuser. His lectures, for example on the “Characteristics of Adornoesque Thinking” or the “Dialectics of Enlightenment” made “authentic study” of critical theory possible in both Lüneburg as well as Frankfurt.
In his philosophical writings, Schweppenhäuser dealt with the self-reflection of dialectical thinking, the philosophy of language, aesthetics and critique of culture and current times as well as with the relationship between philosophy and theology. In the 1970s, he published the Collected Works of Walter Benjamin (Suhrkamp Verlag) together with Rolf Tiedemann. The bequest, numbered as “Na 77 Nachlass Hermann Schweppenhäuser”, includes numerous unpublished texts of many different kinds: from subject-specific deliberations to elegantly formulated aphorisms and fragments to literary productions in the fields of poetry and short prose. Attempts at playwriting from his student days are also waiting in the archive to be discovered. A first small selection of aphorisms from the Schweppenhäuser bequest appeared in the commemorative volume “Image and Idea” (Bild und Gedanke) published in 2016.
The extensive correspondence, which is also part of the bequest, shows just how close the philosopher’s dialogue with international academics was. These included, amongst others, Giorgio Agamben (Italy), Siegfried Kracauer (USA), Herbert Marcuse (USA), Gerard Raulet (France), Gershom Scholem (Israel), Gary Smith (USA), Ulrich Sonnemann (Germany) and Moshe Zuckermann (Israel).
Photos and captions under: www.uni-frankfurt.de/65055989
Further information: Dr. Mathias Jehn, Archive Centre of Johann Christian Senckenberg University Library, Bockenheim Campus, Tel.: +49(69)798-39007, Email: firstname.lastname@example.org