Search

Considering the relevance of hypothalamic astrocytes in the control of metabolism, their molecular and spatial responses to a high-fat high-sugar (HFHS) diet were here investigated. HFHS diet not only induced distinctive transcriptomic and proteomic responses in hypothalamic astrocytes, but also changes in the number and spatial profile of astrocytes expressing distinct molecular markers, specifically in the arcuate nucleus of the hypothalamus (ARC)., Aufgrund der Relevanz von hypothalamischen Astrozyten bei der Kontrolle des Metabolismus wurde hier ihre molekulare und räumliche Antwort auf eine Hochfett-Hochzucker (HFHZ) Diät untersucht. Eine HFHZ Diät induzierte nicht nur eine charakteristische Antwort des Transkriptoms und Proteoms in hypothalamischen Astrozyten, sondern änderte auch die Anzahl und das räumliche Profil von Astrozyten mit charakteristischer Expression molekularer Marker spezifisch im Nucleus arcuatus (ARC) des Hypothalamus.

Cell replacement therapy holds great promise to cure diabetes, however, current stem cell differentiation protocols are inefficient and generate immature beta cells. We identified specified endoderm progenitors for quality control, enrichment and improvement of in vitro beta cell differentiation protocols. Furthermore, in vitro modeling systems to study pancreas development and its associated diseases are critical to understand disease mechanisms and identify targets for therapy. We generated a 3D pancreatic modeling system to analyze dynamic cellular processes ex vivo., Zellersatztherapien mit in vitro generierten Betazellen sind vielversprechend, um Diabetes zu heilen, jedoch sind die aktuellen Differenzierungsprotokolle ineffizient und generieren unreife Betazellen. Wir identifizierten spezifizierte endodermale Vorläuferzellen zur Qualitätskontrolle, Anreicherung und Verbesserung von Betazell-Differenzierungsprotokollen. Des Weiteren sind in vitro Modellsysteme zur Analyse der Pankreasentwicklung und pankreatischen Krankheiten essenziell, um Krankheitsmechanismen und Wirkstoffziele zu identifizieren. Wir etablierten ein 3D-Pankreas Modellsystem, um dynamische zelluläre Prozesse ex vivo zu analysieren.

Cell replacement therapy holds great promise to cure diabetes, however, current stem cell differentiation protocols are inefficient and generate immature beta cells. We identified specified endoderm progenitors for quality control, enrichment and improvement of in vitro beta cell differentiation protocols. Furthermore, in vitro modeling systems to study pancreas development and its associated diseases are critical to understand disease mechanisms and identify targets for therapy. We generated a 3D pancreatic modeling system to analyze dynamic cellular processes ex vivo., Zellersatztherapien mit in vitro generierten Betazellen sind vielversprechend, um Diabetes zu heilen, jedoch sind die aktuellen Differenzierungsprotokolle ineffizient und generieren unreife Betazellen. Wir identifizierten spezifizierte endodermale Vorläuferzellen zur Qualitätskontrolle, Anreicherung und Verbesserung von Betazell-Differenzierungsprotokollen. Des Weiteren sind in vitro Modellsysteme zur Analyse der Pankreasentwicklung und pankreatischen Krankheiten essenziell, um Krankheitsmechanismen und Wirkstoffziele zu identifizieren. Wir etablierten ein 3D-Pankreas Modellsystem, um dynamische zelluläre Prozesse ex vivo zu analysieren.

Adult neurogenesis is restricted to two distinct areas of the mammalian brain: the olfactory bulb (OB) and the dentate gyrus (DG). Despite its spatial restriction, adult neurogenesis is of crucial importance for sensory processing and learning and memory. Although it has been shown that tens of thousands of new neurons arrive in the OB and DG every day with about half of them surviving after integration, the total contribution of adult neurogenesis to the pre-existing network remains mostly unknown. This is because of previous approaches labeling only a small proportion of adult-generated neurons. Here, we used genetic fate mapping to follow the majority of adult-generated neurons over long periods. Our data demonstrate two distinct modes of neuron addition to the pre-existing network. In the glomerular layer of the OB, there is a constant net addition of adult-generated neurons reaching a third of the total neuronal population within 9 months. In contrast, adult neurogenesis contributes to only a minor fraction of the entire neuronal network in the granular cell layer of the OB and the DG. Although the fraction of adult generated neurons can be further increased by an enriched environment, it still remains a minority of the neuronal network in the DG. Thus, neuron addition is distinct and tightly regulated in the neuronal networks that incorporate new neurons life long.

The mechanisms governing the expansion of neuron number in specific brain regions are still poorly understood. Enlarged neuron numbers in different species are often anticipated by increased numbers of progenitors dividing in the subventricular zone. Here we present live imaging analysis of radial glial cells and their progeny in the ventral telencephalon, the region with the largest subventricular zone in the murine brain during neurogenesis. We observe lineage amplification by a new type of progenitor, including bipolar radial glial cells dividing at subapical positions and generating further proliferating progeny. The frequency of this new type of progenitor is increased not only in larger clones of the mouse lateral ganglionic eminence but also in cerebral cortices of gyrated species, and upon inducing gyrification in the murine cerebral cortex. This implies key roles of this new type of radial glia in ontogeny and phylogeny.

The adult mouse subependymal zone (SEZ) harbors neural stem cells that are thought to exclusively generate GABAergic interneurons of the olfactory bulb. We examined the adult generation of glutamatergic juxtaglomerular neurons, which had dendritic arborizations that projected into adjacent glomeruli, identifying them as short-axon cells. Fate mapping revealed that these originate from Neurog2- and Tbr2-expressing progenitors located in the dorsal region of the SEZ. Examination of the progenitors of these glutamatergic interneurons allowed us to determine the sequential expression of transcription factors in these cells that are thought to be hallmarks of glutamatergic neurogenesis in the developing cerebral cortex and adult hippocampus. Indeed, the molecular specification of these SEZ progenitors allowed for their recruitment into the cerebral cortex after a lesion was induced. Taken together, our data indicate that SEZ progenitors not only produce a population of adult-born glutamatergic juxtaglomerular neurons, but may also provide a previously unknown source of progenitors for endogenous repair.

The developmental functionality of neural networks involved in complex diseases, such as addiction, is an important determinant of adult behavior. Thus, understanding the principles of embryonic neurogenesis is of prime importance. To approach this issue, I focused on neurogenesis control in the midbrain-hindbrain domain, which contains a long-lasting progenitor pool, the Intervening zone (IZ). I identified the Hairy/E(Spl) factors Him and Her5 as the crucial determinants of IZ formation. The expression of these two factors at the end of gastrulation prefigures and later during development precisely delineates in space the IZ. The IZ is formed as a two-partite area (lateral (LIZ) and medial (MIZ)), these two domains differing with respect to their sensitivity to the ``Him + Her5'' inhibitory activity. Using single and double knockdowns of him and her5, as well as a him + her5 deletion mutant background b404 , I demonstrated that Him and Her5 are equally necessary for MIZ formation, and that they act redundantly in LIZ formation in vivo. I showed that these processes do not involve cross-regulation between Him and Her5 expression or activities. Increasing the function of one factor when the other is depleted, I further showed that Him and Her5 are functionally interchangeable. My results are in agreement with a model where the global ``Him + Her5'' activity inhibits ngn1 expression in a dose-dependent manner and through different sensitivity thresholds along the medio-lateral axis of the neural plate. I showed that this differential sensitivity of the MIZ and LIZ were based on graded Gli signaling along the medio-lateral neural plate axis at the level of the IZ, and that Gli1 activity in this process was regulated by the PKA/ GSK3beta phosphorylation tandem. According to my results, Gli1 increases the threshold level for ``Him + Her5'' inhibitory activity in the MIZ and loss of Gli1 function render the MIZ into the LIZ in respect to ``Him + Her5'' inhibitory activity, Die Aufklärung der molekularen Prozesse während der embryonalen Neurogenese sind von grundlegender Bedeutung für das Verständnis der Neuronalentwicklung, aber auch zur Aufklärung der Ursachen von neurologischen und psychischen Krankheiten im erwachsenen Alter. Da die Ursachen vieler dieser Krankheiten in einer fehlgeleiteten Embryonalentwicklung liegen, ist es wichtig, die molekularen Grundlagen der embryonalen Neurogenese zu verstehen. Um zu diesem Verständnis beizutragen, untersuchte ich die Kontrolle der Neurogenese in der Mittel/Hinterhirn-Domäne. Ich habe die Hairy/E(Spl) Proteine Him und Her5 als bestimmende Faktoren für die Bildung dieser Domäne identifiziert. Parallel dazu entwickelte ich eine Methodik, mittels derer Gehirnfunktionen in Zebrafischen unter Drogeneinfluß bestimmt werden können. Meine Ergebnisse bilden die Gundlage für den Einsatz von phänotyp-getriebenen Strategien, die erlauben die molekulare Kontrolle der Neurogenese und des Belohnung-Systems zu bestimmen.

The developmental functionality of neural networks involved in complex diseases, such as addiction, is an important determinant of adult behavior. Thus, understanding the principles of embryonic neurogenesis is of prime importance. To approach this issue, I focused on neurogenesis control in the midbrain-hindbrain domain, which contains a long-lasting progenitor pool, the Intervening zone (IZ). I identified the Hairy/E(Spl) factors Him and Her5 as the crucial determinants of IZ formation. The expression of these two factors at the end of gastrulation prefigures and later during development precisely delineates in space the IZ. The IZ is formed as a two-partite area (lateral (LIZ) and medial (MIZ)), these two domains differing with respect to their sensitivity to the ``Him + Her5'' inhibitory activity. Using single and double knockdowns of him and her5, as well as a him + her5 deletion mutant background b404 , I demonstrated that Him and Her5 are equally necessary for MIZ formation, and that they act redundantly in LIZ formation in vivo. I showed that these processes do not involve cross-regulation between Him and Her5 expression or activities. Increasing the function of one factor when the other is depleted, I further showed that Him and Her5 are functionally interchangeable. My results are in agreement with a model where the global ``Him + Her5'' activity inhibits ngn1 expression in a dose-dependent manner and through different sensitivity thresholds along the medio-lateral axis of the neural plate. I showed that this differential sensitivity of the MIZ and LIZ were based on graded Gli signaling along the medio-lateral neural plate axis at the level of the IZ, and that Gli1 activity in this process was regulated by the PKA/ GSK3beta phosphorylation tandem. According to my results, Gli1 increases the threshold level for ``Him + Her5'' inhibitory activity in the MIZ and loss of Gli1 function render the MIZ into the LIZ in respect to ``Him + Her5'' inhibitory activity, Die Aufklärung der molekularen Prozesse während der embryonalen Neurogenese sind von grundlegender Bedeutung für das Verständnis der Neuronalentwicklung, aber auch zur Aufklärung der Ursachen von neurologischen und psychischen Krankheiten im erwachsenen Alter. Da die Ursachen vieler dieser Krankheiten in einer fehlgeleiteten Embryonalentwicklung liegen, ist es wichtig, die molekularen Grundlagen der embryonalen Neurogenese zu verstehen. Um zu diesem Verständnis beizutragen, untersuchte ich die Kontrolle der Neurogenese in der Mittel/Hinterhirn-Domäne. Ich habe die Hairy/E(Spl) Proteine Him und Her5 als bestimmende Faktoren für die Bildung dieser Domäne identifiziert. Parallel dazu entwickelte ich eine Methodik, mittels derer Gehirnfunktionen in Zebrafischen unter Drogeneinfluß bestimmt werden können. Meine Ergebnisse bilden die Gundlage für den Einsatz von phänotyp-getriebenen Strategien, die erlauben die molekulare Kontrolle der Neurogenese und des Belohnung-Systems zu bestimmen.

Adult neurogenesis is restricted to two distinct areas of the mammalian brain: the olfactory bulb (OB) and the dentate gyrus (DG). Despite its spatial restriction, adult neurogenesis is of crucial importance for sensory processing and learning and memory. Although it has been shown that tens of thousands of new neurons arrive in the OB and DG every day with about half of them surviving after integration, the total contribution of adult neurogenesis to the pre-existing network remains mostly unknown. This is because of previous approaches labeling only a small proportion of adult-generated neurons. Here, we used genetic fate mapping to follow the majority of adult-generated neurons over long periods. Our data demonstrate two distinct modes of neuron addition to the pre-existing network. In the glomerular layer of the OB, there is a constant net addition of adult-generated neurons reaching a third of the total neuronal population within 9 months. In contrast, adult neurogenesis contributes to only a minor fraction of the entire neuronal network in the granular cell layer of the OB and the DG. Although the fraction of adult generated neurons can be further increased by an enriched environment, it still remains a minority of the neuronal network in the DG. Thus, neuron addition is distinct and tightly regulated in the neuronal networks that incorporate new neurons life long.