Outreach and Awards Foundation BrainAid/IZN Master Thesis Award

2025

Selma Saisan (Mall lab)

With the use of patient-derived MYT1L iNs and cortical organoids my master thesis identified and characterized patient-specific pathways of MYT1L-associated NDDs. Differential gene expres-sion analysis of the RNA-Seq dataset of patient-derived +/R567P- and +/R75*-iNs revealed tran-scriptional differences between both mutation classes. While distinct genes, including both MYT1L direct and non-direct targets, were deregulated in both patient iNs, the changes con-verged on similar functional pathways, indicating an immature neuronal state, impaired “neuronal identity”, and altered neuronal excitability across patients. This convergence might explain why some common features, such as developmental delay and intellectual disability, exist while many clinical manifestations and their severity differ between patients. To define how MYT1L physiologically regulates transcription, the interactome of MYT1L was iden-tified in an IP-MS analysis in WT-iNs. The analysis revealed that MYT1L interacted with chromatin remodelers including LSD1, PHF21A/B, HDAC2, and CoRESTs which can mediate transcrip-tional repression and activation23-29. This suggests possible dual regulatory functions of MYT1L during transcription. The identification of the MYT1L interactome was then used to elucidate gene expression changes in the patient RNA-Seq dataset in more detail. Investigating the expression of target genes of MYT1L-interactors in the RNA-Seq dataset revealed a deregulation of LSD1 target genes in both patients. This indicates that neurogenesis was not only impaired upon de-regulation of MYT1L but also of LSD1 targets. This suggests that MYT1L might impair the phys-iological function of its interactors upon mutations or acquire novel DNA binding sites, i.e. target sites of its interactors. Additionally, this provides first explanations for the deregulation of MYT1L non-direct targets. Further, with the generation of +/R75*-cortical organoids, MYT1L-associated neurogenic defects were characterized in an in vitro model of human brain organogenesis for the first time. Interest-ingly, patient organoids revealed small neurogenic niches and impaired neuronal maturation over time. Additionally, scRNA-Seq analysis of human MYT1L-KO cortical organoids revealed an over-expression of the NDD-risk gene RBFOX1. RT-qPCR analysis of the +/R75*-cortical organoids confirmed an upregulation of RBFOX1 and identified a so far unreported pathomechanism of MYT1L-associated NDDs. Overall, with the use of two- and three-dimensional preclinical MYT1L platforms my master thesis showed that patient-specific gene expression changes converged on similar functional pathways and that the +/R75*-mutation was associated with small neurogenic niches in cortical organoids. Also, first explanations were found of how MYT1L could repress and activate transcription. These studies contributed to our understanding of how MYT1L mutations result in the spectrum of NDDs and provide a foundation for the development of personalized treatment strategies in the future.

Adriana Schneider (Mauceri lab)

Neurons—the cells that make up our brain and nervous system—are surrounded by a protective layer called the cell membrane, which helps them function and communicate. This membrane is made up of proteins and special fat molecules called phospholipids. One of these lipids, phosphatidylserine (PS), is normally found only on the inside of the cell membrane. If PS appears on the outside, it can be a warning sign that the cell is damaged or dying. This abnormal exposure has been observed in brain disorders like Alzheimer’s disease or after stroke, but scientists still do not fully understand how neurons control the position of PS—especially in fully developed (mature) neurons in the adult brain. In earlier work, our research group discovered that when mature neurons are exposed to toxic stress, which is defined by excessive overstimulation, PS moves to the outside of the membrane. At the same time, the levels of a protein called Atp8a2, which normally helps to keep PS inside, was found to be reduced in this condition. This raised a key question: is the loss of Atp8a2 directly linked to potentially harmful PS exposure? To explore this, in my master thesis I studied how Atp8a2 controls the localization of PS in mature neurons. This aspect is particularly relevant for neurons, which are cells characterized by a very specific tree-like structure essential to properly communicate with one another and ultimately for brain function. I discovered that even under healthy conditions, small amounts of PS are exposed at specific fragile spots on neurons, especially at branch points. When neurons were overstimulated, the amount of exposed PS increased dramatically within these spots. I then used genetic tools to reduce the level of Atp8a2 in neurons and detected that this was sufficient to increase similar PS exposure, even without further stressing the neurons. This showed that Atp8a2 is important for keeping PS inside the membrane of mature neurons. To test whether it is the actual enzymatic function of Atp8a2 that is responsible for this phenomenon, I collaborated with structural biologists to create a specific molecule acting as an Atp8a2 inhibitor and blocking its activity. Treating neurons with this new Atp8a2 inhibitor again caused PS exposure similar to the one I have seen when I reduced the level of Atp8a2, proving that it is not just the presence of Atp8a2 that matters—it is also how well it functions. Importantly, I was able to use my observations to protect neuron from degeneration: when I specifically increased Atp8a2 levels, PS stayed inside and neurons were protected from toxic stress. In summary, my work shows for the first time that Atp8a2 plays a key role in protecting adult neurons by preventing harmful PS exposure to the outside of the cell membrane. These findings reveal a previously unknown mechanism in mature neurons that could open new paths to develop novel strategies for preventing or treating brain diseases linked to damage of neurons.

2024

Sofiya Zbaranska (Monyer lab)

Remember the last time you wished to stay focused on a task such as reading or meditation but had difficulty concentrating? Numerous brain regions work hand in hand to help us maintain attention. The medial septum (MS) is one of these regions, and it communicates with the hippocampus, another structure critical for memory and spatial navigation. One way to ensure coordinated activity of distant brain regions is synchronization of the electrical activity of neurons located in these regions, resulting in detectable activity oscillations. Previous research has elucidated several types of neurons in the MS that control spatial navigation through the modulation of these oscillations. However, one of the neuronal types, which expresses a molecular marker called somatostatin (SOM), has not been studied much. A recent discovery in the Monyer lab shed light on the anatomical connection between these neurons and the hippocampus. Hence, my master’s thesis aimed to take the first steps in elucidating what role septal SOM-positive neurons play in hippocampal processing. Our preliminary findings indicate that activating the projections of septal SOM+ neurons targeting the hippocampus improves the stability of the hippocampal spatial coding. However, we did not find indications of the involvement of these neurons in regulating oscillations in the hippocampus. Furthermore, we detected one septal SOM+ neuron that responded to the presence of objects in the environment. Thus, our data suggest that SOM+ neurons represent a functionally distinct cell type in the MS, which is also reflected by their distinguishable electrophysiological properties. Bridging previous research and our findings, we speculate that these properties of SOM+ neuronal projections to the hippocampus could provide a mechanism for attention modulation and contribute to the efficiency of memory formation. This is the first study investigating the properties of septal SOM+ neuronal connectivity to the hippocampus and its functional relevance. Importantly, it holds the potential to provide valuable insights into cellular and molecular mechanisms of attention, which is known to be impaired in some psychiatric diseases, such as attention-deficit/hyperactivity disorder.

2023

Rangeet Manna (Schlesiger lab)

The craving to take drugs is largely driven by the social setting and physical context in which the drugs are normally taken. For example, an addict who is used to taking drugs in a night club will find it easier to abstain from drug use in a hospital than in a nightclub. These contextual memories are encoded, stored, and recalled by the hippocampal-entorhinal system of our brain. Addictive drugs, such as cocaine, amphetamine, or heroin, drive addiction in humans by directly or indirectly modulating the midbrain dopaminergic system. In my thesis, I mimicked the dopaminergic aspects of these drugs by directly activating the midbrain dopaminergic system in a mouse model while simultaneously recording the activity of individual neuron s in the Lateral Entorhinal Cortex, a key region of the hippocampal-entorhinal system essential for contextual memory. The mice could explore two contexts (environments), a neutral control context and a context paired with the artificial activation of the midbrain dopamine system. The mice developed a strong preference for the context paired with the dopaminergic activation. While mice were exploring this context, there was a significant increase in the precision of contextual coding in neurons in the Lateral Entorhinal Cortex, that is, the brain encoded the rewarded context in greater detail than the non-rewarded context. This increased precision in the contextual coding driven by dopaminergic activation may be the substrate for the context-induced cravings and relapse seen in drug addiction. This work opens the possibility of targeting specific components of the entorhinal system as a basis for therapeutic strategies for targeting context induced cravings.

2022

Stephanie Küppers (Grinevich lab)

The comorbidity of pain disorders and emotional health problems is well documented. More specifically, over half of chronic pain patients suffer from major depressive disorder, and the prevalence of depression and other mental health problem, such as general anxiety disorders and substance use disorders are four times as prevalent compared to the general population. This clearly demonstrates the urgency and importance of treating not only the physical component of acute pain and pain disorders, but also the emotional valence towards pain perception. A promising candidate for treatment of these symptoms is the hypothalamic neuropeptide oxytocin (OT), which exerts not only prominent pro-social and anxiolytic effects, but has also garnered great attention due to its analgesic abilities. Thus, the naturally occurring OT, which functions both as a neurotransmitter in the brain and as a hormone in the periphery, has already been proposed as a treatment for pain disorders, such as low back pain. For my Master study in particular, I was interested in the brain region known as the insular cortex (IC), which integrates pain processing and emotional valence and hence is considered as a target structure for OT action in pain conditions. Considering the involvement of both the OT system and the IC in pain processing, and the occurrence of OT and its receptor in the IC, the interplay between the two systems constitutes a promising target for “emotional analgesia”. In order to investigate the brain circuits and functional role of OT signaling in the IC, in my Master thesis work I utilized a rat model in combination with immunolabelling of OT neurons as well as OT receptive cells in the IC. This allowed me to not only dissect the location, cell-types, and connectivity of OT neurons and neurons expressing its receptor in the IC, but also to modulate their activity. While artificially increasing OT signaling at physiological target sites and concentrations in the IC, I could assess pain-associated behaviors in freely moving rats. Using a well-established paradigm (conditioned place preference test) and a novel behavioral setting (modified operant box) I specifically addressed the perceived and anticipated painfulness of different stimuli, while simultaneously assessing the physical analgesia of OT action. This approach allowed me to show that increasing OT signaling in the IC lead to improved emotional valence towards painful stimuli, but no alterations in physical sensing of pain. Altogether, my Master thesis provides a background for further investigation of OT signaling in the IC in the context of emotional pain processing, which I currently pursue in my PhD work I started in October 2021. Notably, the obtained (as well as very recently gathered) results support the clinical application of OT and especially its new synthetic analogues [5] for clinical treatment of emotional alterations caused by acute and chronic pain.

2021

Kristina Battis (Bading lab)

The ability to rapidly respond to harmful stimuli that might threaten our body was acquired by humans and many other organisms, through evolution, a long time ago. One such system is pain that is essential to an organism’s survival. At the same time, pain occurs as a symptom of a broad range of disorders. In the setting of persistent injury, for example, the nervous system can undergo changes resulting in enhanced pain sensitivity. When these changes persist, a chronic pain condition can occur. In Germany 28% of the population suffers from chronic pain. A special form of chronic pain, is neuropathic pain, that can be caused by damage of the nervous system. Even from neuropathic pain suffers 6% of the german population. The treatment options for chronic pain, as well as neuropathic pain are still very limited. Therefore, we aimed at improving the understanding of the mechanism of neuropathic pain generation. On top of that we wanted to find a possibility to reduce these pain symptoms. In sum, we were able to find an important gene, named Npas4, that together with its signalling pathway plays a major role in the formation of neuropathic pain. By increasing the concentration of this gene in mice we were able to reduce neuropathic pain symptoms. Thus, our findings provide further insight into the generation of neuropathic pain. Moreover, we show for the first time that neuropathic pain can be diminished by increasing Npas4 which gives a direction for the development of a potential therapeutic strategy to improve the live of many people.

2020

Carolin Fischer (Köhr lab)

Emotions have a very diverse and broad spectrum of behaviour which is orchestrated by one of the most complex machineries - the human brain. The limbic system is the region of the brain that is responsible for emotional processing. This centre of emotional processing, in turn, is regulated by the prefrontal cortex, which is often referred to as the rational centre of our brain. Since the prefrontal cortex in children is not yet fully developed, they often show very emotional and uncontrolled behaviour, which highlights the relevance of the prefrontal cortex as centre of emotion regulation. Interestingly, bipolar disorder patients also display an altered brain activity in these two regions: the limbic system displays increased activity, which is associated with a reduced activity of the prefrontal cortex resulting in a failure of emotion regulation. This master thesis investigated the altered regional activity in nerve cells as the smallest unit of the brain. So-called induced pluripotent stem cells (iPSCs) were used to produce cortical nerve cells from bipolar disorder patients in order to investigate the finding of an altered activity in the prefrontal cortex on a single cell level. iPSCs have two major advantages in the context of this master thesis: First of all, it allows the generation of human nerve cells, which otherwise would be difficult to obtain. In addition, patient-specific cells carry their unique genetic constellation and thus allow the analysis and modelling of human diseases ‘in a dish’. The activity of nerve cells of cortical origin from bipolar disorder patients was compared with that of healthy control cells, whereby the patient cells showed reduced activity. Furthermore, this work gave first indications that lithium, as the most commonly used therapy for treatment of bipolar disorder, can in turn increase the activity of cortical nerve cells. This master thesis complements the study of Mertens et al., who examined the activity of nerve cells of limbic origin and showed an increased neuronal activity. Thus, this data indicates that region-specific differences in activity are reflected by the iPSC-model system. Most importantly, this opens up new possibilities to deepen research with patient-specific nerve cells and investigate the underlying cellular mechanisms of an altered activity of nerve cells.

2019

Katja Baur (Ciccolini lab)

Primary cilia are tiny, rod-shaped cellular organelles which were once thought to be vestigial. In the adult mammalian brain, the surface of the subventricular zone (SVZ), which lines the lateral ventricles, is covered by many motile ependymal cilia and only few primary cilia originating from rare intermingled neural stem cells (NSCs). In NSCs, the primary cilia were recently found to be key for the transduction of extracellular signals essential for the maintenance, proliferation, migration and differentiation of NSCs, and therefore play a role development, learning and memory. Ablation of primary cilia leads to defects in development, and a growing number of diseases termed “ciliopathies” have been associated with cilia dysfunction. Despite their importance, the analysis of NSC primary cilia is greatly hampered by the fact that they are overwhelmingly outnumbered by the motile cilia. In my Master’s Thesis titled “Isolation and analysis of primary cilia from the murine subventricular zone with a novel flow cytometry-based approach”, I developed and validated a new method to selectively isolate primary cilia from the SVZ using flow cytometry and established cilia markers. With the flow cytometer, primary cilia can be easily separated from motile cilia at speeds of over 3000 cilia per second. I validated the method using immunofluorescence, western blot and electron microscopy and showed that this approach can also be used to study dynamic mechanisms in cilia. With this new, innovative method, primary cilia of NSCs can be isolated and purified for full proteomic analysis, as well as directly analysed for marker expression and corresponding dynamics. All in all, this method is a new tool for the investigation of the poorly understood primary cilia and their role in development and disease.

2018

Melina Castelanelli (Draguhn lab)

Life without the ability to learn and remember means to forget people and places we once knew, no longer being able to execute skills we once learned or to recall the happiest or saddest moments of our lives. Hence, the ability to form memories is essential for what defines us as human beings. However, it still remains a mystery how and where the brain stores information either as short- or long-term memory. The transition from short- to long-term memory by strengthening newly acquired information into more stable forms is called consolidation. It is generally thought that this consolidation involves the transfer from a specific brain region, the hippocampus, to a larger area, called cortex. Interactions between brain areas are coordinated through a multitude of periodically fluctuating waves of different shapes, contributing to the different brain rhythms. During sleep or rest, waves generated in the hippocampus often synchronize with those from the cortex and thus tend to occur at approximately the same time. Such synchronous activities of large groups of neurons sum up and can be detected - and recorded – in a way comparable to measuring heart-activity by an electrocardiogram (ECG). Many neuroscientists believe that neuronal synchronization mediates communication between different brain regions. In turn, the occurrence of synchronized hippocampal and cortical waves might help to strengthen transient memories. Recent studies support this view by showing that disruption of hippocampal-cortical communication impairs the formation of short- and long-term memory. This was achieved by applying electrical currents, a well established approach that is, however, accompanied by many side effects. Thus, the aim of my Master Thesis was to develop a more sophisticated way, to disable the interaction between hippocampus and cortex, using a method called optogenetics. By spatial restricted application of light in the brain, this method allows for controlling neuronal communication in a target area, only affecting desired neurons while having no effect on neighboring ones. Further, I implemented a task that allows for testing short- and long-term memory formation in mice. This provides a readout for the impact of optogenetic intervention on hippocampal-cortical interactions on memory consolidation. The work of my Master Thesis paves the way for investigating memory consolidation in a unique and highly selective way. This contributes to unravel the mechanisms underlying memory formation and does not only serve basic research, but rather helps to understand and eventually treat diseases related with memory loss.

2017

Constanze Depp (Bas Orth lab)

Excitotoxicity describes the process of pathological overstimulation of certain neurotransmitter receptors in nerve cells that leads to cell death. The work in my master thesis contributes to our understanding how active neurons protect themselves against this harmful condition. Key to this protective shield is the protection of mitochondria, small cellular organelles. Mitochondria are normally of elongated shape and function to provide cells with energy. As byproduct of their powerhouse machinery mitochondria produce small amounts of reactive oxygen species which in excess can damage important cell components. In my master thesis, I used a new tool to show that mitochondria in neurons experience such oxidative damage and accompanying shrinkage during excitotoxicity. I could demonstrate that active neurons show less oxidative damage and structural collapse of their mitochondria during excitotoxicity. Mechanistically, this seems to work mainly via a reduction of the amount of calcium ions that can enter mitochondria through a mitochondrial ion channel. Synaptic activity appears to silence the production of this ion channel, thereby reducing mitochondrial calcium levels and its pathological consequences such as oxidative damage. Since excitotoxicity and mitochondrial oxidative damage are key features of neurodegenerative diseases such as Alzheimer’s Disease or Huntington’s Disease these findings also have clinical relevance: First, they highlight the importance of maintaining an active lifestyle to keep brain activity high while we age and become susceptible to neurodegenerative diseases (“an active brain is a healthy brain”). Second, they identify the mitochondrial calcium ion channel as a possible drug target to reduce oxidative damage to mitochondria during neurodegeneration.