The Konnerth group concentrates on the mechanisms of synaptic wiring in the developing mammalian cortex. Various high-resolution optical and electrophysiological techniques are used for the assessment of those electrical signals that are able to mobilize second messengers (e.g. Ca and/or cAMP), which are required for activity-dependent synaptic plasticity. Of special interest is a new form of instantly-induced long-term potentiation (LTP). This LTP is induced by a single afferent shock and may be the basis of the rapid acquisition of memories.

The Hofmann group is currently testing the hypothesis that for the induction of synaptic plasticity either CaM or CaM kinase II trigger gene transcription, whereas the elevation of postsynaptic [Ca2+]i by itself has no effect on the transcription or L-LTP. They will modify the CaM-binding site (IQ motive) at the cytosolic C-terminus of the Cav1.2 protein. The modification of the Cav1.2 gene is associated with embryonic lethality. Therefore, they will introduce a tissue-specific gene modification and expect reduced spatial learning in the modified animals, if all predictions are correct. For the creation of a further and additional mouse line, they will inactivate the putative cAMP kinase site at Ser-1928. This modification will allow to investigate the biological effects of cAMP-dependent phosphorylation of the neuronal L-type Ca2+ channel.

The Haass group develops biochemical, cellular, and in vivo techniques for truly interdisciplinary research. Caenorabditis elegans is used to work out the biological function of Presenilin in Notch signaling and the role of the active site domain. Recently, they established the zebrafish model to investigate the function of genes associated with neurodegeneration and regulated intramembrane proteolysis. In addition the Haass laboratory is very interested in the cellular function and dysfunction of ß-Secretase (BACE-1) and -secretase. After demonstrating the cellular targeting of these proteases to their substrates, they are now investigating the physiological function and the regulation of these proteases during aging. Currently, a major focus is on the identification of a physiological substrate of BACE-1. Neuregulin has been recently identified as a physiological substrate for BACE-1. Moreover, BACE-1 mediated processing of Neuregulin is required for myelinization. Finally, regulation of BACE-1 was found to occur at the posttranscriptional level via its 5' untranslated region. Importantly, during AD, aging, and upon trauma BACE-1 protein, but not mRNA is upregulated.

The main aim of the Götz group within this network is to identify the protein-protein interactions of the different domains of Pax6 and understand how they influence transcription of down-stream targets. They will perform proteomic analysis of the paired and homeodomains of Pax6 as well as the full-length protein in the context of brain neural stem cells as well as retinal stem cells in collaborations within this network. Since they have access to a pure, defined population of neural stem cells derived from embryonic stem cells where Pax6 is homogeneously expressed in all cells and is required for their differentiation into glutamatergic neurons. These cells can be used as source for biochemical experiments, while primary cells will be sorted to purity by fluorescence-activated cell sorting. Purified Pax6 protein and its subdomains will also be examined in regard to their interaction with the basic transcriptional machinery in collaboration with Patrick Cramer. Moreover, several lines of evidence suggest that Pax6 activation modifies the histone code opening chromatin to allow transcription at several target sites. These interactions will be studied in close collaboration with the group of Peter Becker. These experiments will then be expanded to other key fate determinants that we have examined at the functional level (Ngn2, Mash1, Otx2) to approach a complete systems knowledge of the transcriptional networks active in stem cells directing their differentiation towards specific types of progeny.

The Biel group is currently investigating the molecular pathways underlying apoptotic cell death in CNGA3 and CNGB1-deficient retinae. To this end alterations in gene expression pattern and proteomic approachesare being performed. These studies will be in close cooperation with the groups of Christian Haass and Peter Becker. Moreover, functional studies using lentiviral vectors aiming to rescue CNG channel function in the retina and olfactory receptor neurons will be performed. We are also in the process to generate mouse lines with cAMP deficient HCN2 and HCN4 genes (HCN2cad, HCN4cad). These studies will be complemented by the generation of mouse lines in which HCN1 and HCN4 genes are expressed under the control of the HCN2 promotor (HCN channel “switch” mice). The consequences of these genetic manipulations on the function of neuronal circuits will be investigated using a multidisciplinary approach. These studies will be in cooperation with the groups of Arthur Konnerth and Franz Hofmann.

The Grothe group is currently testing the new concepts concerning the contribution of temporally precise inhibitory transmission by altering the timing of inhibitory components in time processing neuronal circuits. Technically these alterations, changing the neuronal circuit, can be achieved by in vivo injections of viral vectors delivering genetic manipulations of defined proteins into specific auditory brainstem nuclei. The induced alterations in information processing will be detected by physiological in vivo recordings. The underlying changes on the cellular level will be analyzed by conducting in situ patch-clamp recordings. The distribution of receptors will be imaged using high resolution microscopy. Initial alterations within the MNTB will focus on over-expressing HmK toxin blocking Kv1.2 channels and mutated (L-Y) non-desensitizing AMPA-receptor channel sub-units. Further, the location of the post-synaptic AMPA-receptor within the post-synaptic density will be changed by dominant negative over expression of the regulatory protein stargazing. Protein expression-profiles will be investigated in animals were experience dependent plasticity was used to alter the properties within the neuronal circuit. The group attempts to identify the signaling cascade that leads to glycine receptor distributions obtained during proper sound perceptions.