Förderung 2016

“Role of nuclear pore complex dysfunction in cell cycle-related neurodegeneration of the aging and diseased CNS”

Summary:

Perturbances in nucleo-cytoplasmic protein trafficking contribute to cellular pathology in several proteinopathies of the CNS including amyotrophic lateral sclerosis (ALS). Cytotoxicity of aggregated proteins is compartment-specific even at identical biochemical structure, as exemplified for ß-amyloid, mutated huntingtin, or TDP-43 [1,2]. As a putative novel class of molecules involved, we recently identified disturbances in the subcellular distribution of cell cycle (CC) regulatory Cdk4 and Cdk5, with Cdk5 featuring a striking nuclear reduction in α-motor neurons of hSOD1G93A transgenic mice, an animal model of familiar ALS. Nuclear Cdk5 is essential to maintain a continuous postmitotic state in neurons, whereas its nuclear depletion contributes to neuronal dysfunction and death by re-initiation of unscheduled, abortive CC activity [3-6].

Subcellular mislocalization of G1-regulatory Cdk4/5 is thus suggestive to cause cytotoxicity similar to TDP-43 and β-amyloid in ALS and Alzheimer pathology, respectively, through detrimental CC re-activation in neurons. The cellular and molecular cues regulating subcellular CC protein compartmentalization, however, are not yet understood. We assume that a dysfunction of the nuclear pore complex (NPC), the essential structure in mediating bidirectional trafficking and proper distribution of most proteins within the cell [7], is causal for CC protein displacement and related neuronal death observed in CNS aging and pathology. As a mechanism structurally and functionally associated with the NPC, we will further investigate nuclear lamina dispersion as a function of neurosenescence and ALS pathology.

In summary, the project will elucidate the interplay between nuclear membrane dysfunction and detrimental consequences of ‘replicative reprogramming’ in the context of CNS aging and exemplify it for ALS pathology. Therapeutic interference with pathomechanisms involved might open novel targets to prevent or halt age-related dysfunction and neurodegeneration in different disease entities, and carry fundamental and clinical relevance.

References:

1. Woerner AC, Frottin F, Hornburg D, Feng LR, Meissner F, Patra M, Tatzelt J, Mann M, Winklhofer KF, Hartl FU, Hipp MS. (2016) Cytoplasmic protein aggregates interfere with nucleocytoplasmic transport of protein and RNA. Science 351(6269):173-176.
2. Zhang K, Donnelly CJ, Haeusler AR, Grima JC, Machamer JB, Steinwald P, Daley EL, Miller SJ, Cunningham KM, Vidensky S, Gupta S, Thomas MA, Hong I, Chiu SL, Huganir RL, Ostrow LW, Matunis MJ, Wang J, Sattler R, Lloyd TE, Rothstein JD (2015) The C9orf72 repeat expansion disrupts nucleocytoplasmic transport. Nature 525(7567):56-61. 
3. Zhang J, Cicero SA, Wang L, Romito-DiGiacomo RR, Yang Y, Herrup K (2008) Nuclear localization of Cdk5 is a key determinant in the postmitotic state of neurons. Proc Natl Acad Sci U S A. 105(25):8772–8777.
4. Zhang J, Li H, Herrup K (2010) Cdk5 nuclear localization is p27-dependent in nerve cells: implications for cell cycle suppression and caspase-3 activation. J Biol Chem 285(18):14052-61.
5. Zhang J, Li H, Yabut O, Fitzpatrick H, D'Arcangelo G, Herrup K (2010) Cdk5 suppresses the neuronal cell cycle by disrupting the E2F1-DP1 complex. J Neurosci 30(15):5219-28. 
6. Zhang J, Herrup K (2011) Nucleocytoplasmic Cdk5 is involved in neuronal cell cycle and death in post-mitotic neurons. Cell Cycle 10(8):1208-1214.
7. D’Angelo MA, Hetzer MW (2008) Structure, dynamics and function of the nuclear pore complexes. Trends Cell Biol 18(10):456-66. 

Förderung 2016

"Bone metabolism and Lipotoxicity in Obesity"

Summary:

This application addresses the mechanisms underlying bone loss in obesity. We will analyze fundamental molecular pathways regulating bone homeostasis in obesity and define how these are modulated in response to periodontal bacterial infection.

The central hypothesis of the application is that excessive accumulation of saturated palmitic acid (PA) and downstream lipotoxic metabolic intermediates impact bone metabolism and modulates how bone responds to periodontal bacterial infection in obesity. Aim 1 will systematically analyze how saturated PA impacts bone structure and remodeling. We will define which lipid metabolites accumulate in bone and surrounding tissue to identify potential molecular pathways that drive bone loss in obesity. In Aim 2, we will evaluate how osteoblast and osteoclast cellular interactions are influenced by elevated fatty acids (FA). Aim 3 will investigate molecular mechanisms regulating local alveolar bone loss in periodontal infections to determine the impact of inflammatory changes on bone catabolism in obesity. Further, we will test whether pharmacologic inhibition of ceramide metabolism reducing lipotoxicity affects periodontal bone loss in obese animals on a high fat PA diet. In summary, our studies will broaden the understanding of the growing obesity epidemic and test novel therapeutic strategies that may ultimately lead to the identification of targets for new innovative therapeutic interventions counteracting bone loss.

Förderung 2016

"The epigenetic modulation of cortical interneuron survival by the DNA- methyltransferase 1 (DNMT1) over life time"

Summary

Age-related constraints, like cognitive decline, deficits in sensory perception and motor performances of elderly, rather rely on structural and functional defects of particular neuronal cell- types than an overall neuronal loss. Dysregulated gene expression is thought to contribute to age- associated neuronal impairments, which in turn depend on genetic and epigenetic factors  [1].

Epigenetic gene regulation by DNA methylation, executed by DNA-methyltransferases (DNMTs), and histone modifications seem to be critical for the maintenance of neuronal health and function throughout the entire lifespan [3]. Our previous data provide evidence that in the mouse model system DNMT1 function is associated with a vulnerability of inhibitory cortical interneurons towards aging, which constitute essential key players of information processing in the cerebral cortex. Additionally, DNMT1 seems to be required for normal interneuron function in young mice, suggesting stage-dependent modes of action. In addition to DNA methylation, DNMTs interact with histone modifications, enabling various facets of epigenetic gene regulation [5]. Hence, the ultimate goal of this proposal is to approach the diverse DNMT1-dependent epigenetic mechanisms of transcriptional control that contribute to the loss of cortical interneurons in aged mice by integrating its function in modulating neuronal activity over life time.

Project-related publications

Zimmer G, Garcez P, Rudolph J, Niehage R, Weth F, Lent R, Bolz J. Ephrin-A5 acts as a repulsive cue for migrating cortical interneurons. Eur J Neurosci 2008; 28:62-73.
Zimmer G, Schanuel SM, Burger S, Weth F, Steinecke A, Bolz J, Lent R. Chondroitin Sulfate Acts in Concert with Semaphorin 3A to Guide Tangential Migration of Cortical Interneurons in the Ventral Telencephalon. Cerebral Cortex 2010; (10):2411-22
Rudolph J, Zimmer G, Steinecke A, Barchmann S, Bolz J. Ephrins guide migrating cortical interneurons in the basal telencephalon. Cell Adh Migr 2010; 4.
Zimmer G, Rudolph J, Landmann J, Gerstmann K, Steinecke A, Gampe C and Bolz J. Bidirectional ephrinB3/EphA4 signaling mediates the segregation of MGE‑and POA derived interneurons in the deep and superficial migratory stream. J Neurosci 2011; 31(50):18364-80.
Rudolph J, Gerstmann K, Zimmer G, Steinecke A, Döding A and Bolz J. A dual role of EphB1/ephrinB3 reverse signaling on migrating striatal and cortical neurons originating in the preoptic area: should I stay of g  o away? Frontiers in Cellular Neuroscience. 2014 July; 18 (8)
Steinecke A, Gampe C, Zimmer G, Rudolph J, Bolz J. EphA/ephrin-A Reverse Signaling Promotes the Migration of MGE-derived Cortical Interneurons. Development. 2014 Jan;141(2):460-71.
Rüdiger T, Zimmer G , Barchmann S, Castellani V, Bagnard D and Bolz J. Integration of opposing semaphorin guidance cues in cortical axons. Cerebral Cortex 2013 Mar;23(3):604‑14
Blümel L, Pensold D, Khundadze M and Zimmer G. Curbing Methylation: A Key to Eternal Youth And Vigor?International Journal of Neural Science and Brain Research. 2014 August.
Gerstmann K, Pensold D, Symmank J, Khundadze M, Hübner Ch, Bolz J and Zimmer G. Thalamic afferents influence cortical progenitors via ephrinA5/EphA4 interactions. Development. 2015 Jan 1;142(1):140-50
Gerstmann K and Zimmer G. Fine-tuning of cortical progenitor proliferation by thalamic afferents. Neural Regen Res. 2015 June 10(6):887-8
Pensold D, Symmank J, Hahn A, Rotzsch A, Haag N, Andreas N, Schubert K, Salinas-Riester G, Downie BR, Ludewig F, Hübner CA, Pieler T & Zimmer G. DNMT1 controls the migratory shape and dynamics of immature cortical interneurons. In Revision.

Förderung 2018

"Targeting the interaction between bone marrow stromal cells and malignant plasma cells to inhibit multiple myeloma disease progression"

Summary

Multiple myeloma (MM), one of the most prevalent hematological malignancies, affects mainly elderly individuals (median age at diagnosis 69 years). Despite progresses made, MM is still incurable and treatment of older patients is a challenge, due to reduced tolerability and high rate of side effects. One of the most important characteristics of MM is the dependency of the MM cells for their growth and survival on the interaction with bone marrow stromal cells (BMSCs). Another important feature of MM is that it develops following a multistep process, from premalignant stages to active and aggressive stages. Only few genetic changes occur in the transition from the presymptomatic condition to active MM, suggesting that other mechanisms also play a role in disease progression. We hypothesize that disease progression is influenced by molecular changes in BMSCs. To test our hypothesis, BMSCs derived from MM patients in different disease phases will be investigated from a genetic and metabolic point of view, alone and after co-culture with MM cell lines. Identification of differences in BMSCs as well as in the co-cultured MM plasma cells will provide a deeper insight into MM pathobiology. Furthermore, a focused screen of epigenetic drugs will be performed, aiming to find new combination therapies that, with low toxicity, could potentially prevent MM progression by interference in the crosstalk between BMSCs and MM cells.

Förderung 2018

"Effects of physiological and pathological trophoblast-derived extracellular vesicles on the blood-brain-barrier and microglia"

Summary

During pregnancy, biochemical and structural changes in the brain adapt maternal physiology and behavior to ensure offspring survival. Remarkably, little is known about the molecular and cellular mechanisms that govern these processes and how they are influenced by pregnancy pathologies. Placental cells release extracellular vesicles (EVs) into the maternal blood as a mechanism of maternal-fetal communication. Although evidence shows that placental EVs mediate immune tolerance and cardiovascular adaptations in the maternal organism, their functions in the nervous system remains to be investigated. We hypothesize that placental EVs induce changes in the blood brain barrier (BBB) and modulate microglia cell responses. Moreover, these EVs may be the missing link between the placenta and neurologic manifestations of pre-eclampsia. A 3D BBB model in a microfluidic biochip will be employed to investigate BBB structure and properties under the effects of healthy and pre-eclamptic placental EVs. Additionally, mechanisms of placental EV uptake by microglia cells and their activation will be investigated. This proposal strengths a new research field in our group focused on understanding the biological mechanisms involved in the communication between placenta and brain in normal and pathological human pregnancies.

Förderung 2018

"Expansion of radial glia-like stem cells by modulation of intracellular chloride concentration in the hippocampal dentate gyrus during aging"

Summary

Aging is the most important contributing factor for the decrease of radial glia-like stem cells (RGLs) and neurogenesis in the healthy brain. The underlying causes of this age-dependent decline may comprise an increase in RGL quiescence or reduction of RGL self-renewal. We previously determined a cation chloride co-transporter Na+-K+-2Cl− (NKCC1) dependent activation of RGLs that resulted in an increase of RGL self-renewal in the hippocampal dentate gyrus during aging. NKCC1 is predominantly expressed in neural precursor cells and drives Cl− influx. However, the underlying mechanisms of intracellular chloride levels on RGL activation during aging are as yet unknown and are the aim of the present proposal. The research work will be undertaken in three project steps A, B & C. In the first project, we intend to identify the frequency and mode of RGL division (Project A) using the cell cycle indicator mouse model. In the second set of experiments, we will determine the chloride-dependent changes in the RGLs using optogenetic approaches employing halorhodopsin mice (Project B). In the third project, we aim to elucidate the underlying mechanisms of RGL self-renewal by focusing on single cell RNA sequencing (Project C). Determining the dynamics of RGL self-renewal is essential to understanding the mechanisms of the declining potential of RGLs for repair during aging.