News

Friederike returns from Pennsylvania

October 17, 2022

Friederike came back from a 6-month research stay at Ma lab, University of Pennsylvania, Philadelphia. She learned to do in vivo virus-injections into the accessory olfactory bulb. These injections were used to chemogenetically inhibit Mitral cells during behavioural experiments.

News from ECRO 2022

September 4, 2022

Marc Spehr, Andres Hernandez-Clavijo, Hannah-Lena Tröger, Moritz Nesseler, Lena Terlau and Victoria Switacz participated in the annual meeting of the European Chemoreception Research Organization (ECRO) 2022—which took place in August in Berlin, Germany. An excellent opportunity to network and meet fellow scientists! See you again in Nijmegen, the Netherlands, for ECRO 2023!

News from ASA 2022

July 1, 2022

On the annual meeting of the American Society for Andrology (ASA) 2022—which took place in May in La Jolla, California, USA—Lina Kenzler presented her data and was awarded an ASA travel award as well as a travel grant from the Male Contraceptive Initiative (MCI).

New Publication: Ventral striatal islands of Calleja neurons control grooming in mice

November 30, 2021

Zhang Y, Vargas Cifuentes L, Wright K, Bhattarai J, Mohrhardt J, Fleck D, Janke E, Jiang C, Cranfill S, Goldstein N, chreck M, Moberly A, Yu Y, Arenkiel B, Betley J, Luo W, Stegmaier J, Wesson D, Spehr M, Fuccillo M, Ma M (2021) Ventral striatal islands of Calleja neurons control grooming in mice. Nature Neuroscience 24 (12). DOI: 10.1038/s41593-021-00952-z

Show abstract
The striatum comprises multiple subdivisions and neural circuits that differentially control motor output. The islands of Calleja (IC) contain clusters of densely packed granule cells situated in the ventral striatum, predominantly in the olfactory tubercle (OT). Characterized by expression of the D3 dopamine receptor, the IC are evolutionally conserved, but have undefined functions. Here, we show that optogenetic activation of OT D3 neurons robustly initiates self-grooming in mice while suppressing other ongoing behaviors. Conversely, optogenetic inhibition of these neurons halts ongoing grooming, and genetic ablation reduces spontaneous grooming. Furthermore, OT D3 neurons show increased activity before and during grooming and influence local striatal output via synaptic connections with neighboring OT neurons (primarily spiny projection neurons), whose firing rates display grooming-related modulation. Our study uncovers a new role of the ventral striatum’s IC in regulating motor output and has important implications for the neural control of grooming.

News from SSR 2021

November 19, 2021

On the annual meeting of the Society for the Study of Reproduction (SSR) 2021 which will take place in December in Saint-Louis, Missouri, USA, Lina Kenzler and Justine Fischoeder will present their respective data in posters as well as in virtual flash talks.

Lina Kenzler was awarded an SSR trainee-travel award. Justine won an SSR trainee-travel award as well and also received travel grants from the Male Contraceptive Initiative (MCI) and the Molecular Science & Engineering Profile Area.

New Publication: ATP activation of peritubular cells drives testicular sperm transport

January 29, 2021

David Fleck, Lina Kenzler, Nadine Mundt, Martin Strauch, Naofumi Uesaka, Robert Moosmann, Felicitas Bruentgens, Annika Missel, Artur Mayerhofer, Dorit Merhof, Jennifer Spehr, Marc Spehr (2021) ATP activation of peritubular cells drives testicular sperm transport. eLife 2021;10:e62885.
DOI: https://doi.org/10.7554/eLife.62885
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Show abstract
Spermatogenesis, the complex process of male germ cell proliferation, differentiation, and maturation, is the basis of male fertility. In the seminiferous tubules of the testes, spermatozoa are constantly generated from spermatogonial stem cells through a stereotyped sequence of mitotic and meiotic divisions. The basic physiological principles, however, that control both maturation and luminal transport of the still immotile spermatozoa within the seminiferous tubules remain poorly, if at all, defined. Here, we show that coordinated contractions of smooth muscle-like testicular peritubular cells provide the propulsive force for luminal sperm transport toward the rete testis. Using a mouse model for in vivo imaging, we describe and quantify spontaneous tubular contractions and show a causal relationship between peritubular Ca2+ waves and peristaltic transport. Moreover, we identify P2 receptor-dependent purinergic signaling pathways as physiological triggers of tubular contractions both in vitro and in vivo. When challenged with extracellular ATP, transport of luminal content inside the seminiferous tubules displays stage-dependent directionality. We thus suggest that paracrine purinergic signaling coordinates peristaltic recurrent contractions of the mouse seminiferous tubules to propel immotile spermatozoa to the rete testis.

New Publication: Influence of Size and Cross-Linking Density of Microgels on Cellular Uptake and Uptake Kinetics

May 27, 2020

Victoria K Switacz, Sarah K. Wypysek, Rudolf Degen, Jérôme J. Crassous, Marc Spehr and Walter Richtering (2020) Influence of Size and Cross-Linking Density of Microgels on Cellular Uptake and Uptake Kinetics. Biomacromolecules.
DOI: https://doi.org/10.1021/acs.biomac.0c00478

Show abstract
The unique pH and temperature responsiveness of PNIPAM-based microgels make them a promising target for novel biomedical applications such as cellular drug delivery systems. However, we lack a comprehensive understanding of how the physicochemical properties of microgels relate to their interaction with cells. Here, we show that HEK293T cells take up PNIPAM-based microgels on a second-to-minute time scale. Uptake rates are determined by microgel size and cross-linker content. Using fluorescence confocal live-cell microscopy, we observe microgel uptake in real time and describe cellular uptake kinetics. Experiments reveal that small and less cross-linked microgels show faster uptake kinetics than microgels of larger size or higher cross-linker content. Only microgels that are larger than 800 nm in diameter and have cross-linking contents of 10–15 mol % do not show translocation into cells. Together, these results provide insight into microgel–cell interactions and generate quantitative information on the deterministic role of microgel architecture—i.e., size and rigidity—for uptake by a prototypical human cell line.

New Publication: Synchronous Infra-Slow Oscillations Organize Ensembles of Accessory Olfactory Bulb Projection Neurons into Distinct Microcircuits

May 20, 2020

Chryssanthi Tsitoura, Sebastian T. Malinowski, Julia Mohrhardt, Rudolf Degen, Brett T. DiBenedictis, Yuan Gao, Katja Watznauer, Kira Gerhold, Maximilian Nagel, Monika Weber, Markus Rothermel, Ileana L. Hanganu-Opatz, Yoram Ben-Shaul, Ian G. Davison and Marc Spehr (2020) Synchronous Infra-Slow Oscillations Organize Ensembles of Accessory Olfactory Bulb Projection Neurons into Distinct Microcircuits. Journal of Neuroscience 40 (21).
DOI: https://doi.org/10.1523/JNEUROSCI.2925-19.2020

Show abstract
The accessory olfactory system controls social and sexual behavior. In the mouse accessory olfactory bulb, the first central stage of information processing along the accessory olfactory pathway, projection neurons (mitral cells) display infra-slow oscillatory discharge with remarkable periodicity. The physiological mechanisms that underlie this default output state, however, remain controversial. Moreover, whether such rhythmic infra-slow activity patterns exist in awake behaving mice and whether such activity reflects the functional organization of the accessory olfactory bulb circuitry remain unclear. Here, we hypothesize that mitral cell ensembles form synchronized microcircuits that subdivide the accessory olfactory bulb into segregated functional clusters. We use a miniature microscope to image the Ca2+ dynamics within the apical dendritic compartments of large mitral cell ensembles in vivo. We show that infra-slow periodic patterns of concerted neural activity, indeed, reflect the idle state of accessory olfactory bulb output in awake male and female mice. Ca2+ activity profiles are distinct and glomerulus-specific. Confocal time-lapse imaging in acute slices reveals that groups of mitral cells assemble into microcircuits that exhibit correlated Ca2+ signals. Moreover, electrophysiological profiling of synaptic connectivity indicates functional coupling between mitral cells. Our results suggest that both intrinsically rhythmogenic neurons and neurons entrained by fast synaptic drive are key elements in organizing the accessory olfactory bulb into functional microcircuits, each characterized by a distinct default pattern of infra-slow rhythmicity.

Nadine Mundt was accepted as a young scientist and invited to the 70th Lindau Nobel Laureate Meeting 2020! Congratulations, Nadine!

March 4, 2020
© Lindau Nobel Laureate Meetings

Nadine is one of 660 young scientists from 101 countries who were selected to participate in the Lindau Nobel Laureate Meeting from 28th June – 3rd July 2020 in Lindau, Germany. At the meeting she will have the unique opportunity to meet around 70 Nobel Laureates. Since 1951 this meeting has been a great opportunity for cross-generational and interdisciplinary exchange. Surely, attending this unique international scientific forum will be a great and inspiring experience.

For more information see www.lindau-nobel.org.

News from SSR 2019

July 21, 2019

On the Annual Meeting of the Society for the Study of Reproduction (SSR) 2019 in San Jose, California, USA, Dr. David Fleck, Nadine Mundt and Lina Kenzler will present their respective data in oral presentations. Justine Fischoeder will present her data on posters and in a flash talk.

Justine was awarded a Travel Grant from the Male Contraceptive Initiative (MCI), Nadine and Lina each won an Best International Abstract Award.

Nadine won an SSR trainee-travel Award, Lina was awarded the Lalor Foundation Merit Award.