Christian Thome

All Publications

• Depolarization and Hyperexcitability of Cortical Motor Neurons after Spinal Cord Injury Associates with Reduced HCN Channel Activity. International journal of molecular sciences Benedetti, B., Bieler, L., Erhardt-Kreutzer, C., Jakubecova, D., Benedetti, A., Reisinger, M., Dannehl, D., Thome, C., Engelhardt, M., Couillard-Despres, S. 2023; 24 (5)

  Abstract

  A spinal cord injury (SCI) damages the axonal projections of neurons residing in the neocortex. This axotomy changes cortical excitability and results in dysfunctional activity and output of infragranular cortical layers. Thus, addressing cortical pathophysiology after SCI will be instrumental in promoting recovery. However, the cellular and molecular mechanisms of cortical dysfunction after SCI are poorly resolved. In this study, we determined that the principal neurons of the primary motor cortex layer V (M1LV), those suffering from axotomy upon SCI, become hyperexcitable following injury. Therefore, we questioned the role of hyperpolarization cyclic nucleotide gated channels (HCN channels) in this context. Patch clamp experiments on axotomized M1LV neurons and acute pharmacological manipulation of HCN channels allowed us to resolve a dysfunctional mechanism controlling intrinsic neuronal excitability one week after SCI. Some axotomized M1LV neurons became excessively depolarized. In those cells, the HCN channels were less active and less relevant to control neuronal excitability because the membrane potential exceeded the window of HCN channel activation. Care should be taken when manipulating HCN channels pharmacologically after SCI. Even though the dysfunction of HCN channels partakes in the pathophysiology of axotomized M1LV neurons, their dysfunctional contribution varies remarkably between neurons and combines with other pathophysiological mechanisms.

  View details for DOI 10.3390/ijms24054715

  View details for PubMedID 36902146

• Dendritic axon origin enables information gating by perisomatic inhibition in pyramidal neurons. Science (New York, N.Y.) Hodapp, A., Kaiser, M. E., Thome, C., Ding, L., Rozov, A., Klumpp, M., Stevens, N., Stingl, M., Sackmann, T., Lehmann, N., Draguhn, A., Burgalossi, A., Engelhardt, M., Both, M. 2022; 377 (6613): 1448-1452

  Abstract

  Information processing in neuronal networks involves the recruitment of selected neurons into coordinated spatiotemporal activity patterns. This sparse activation results from widespread synaptic inhibition in conjunction with neuron-specific synaptic excitation. We report the selective recruitment of hippocampal pyramidal cells into patterned network activity. During ripple oscillations in awake mice, spiking is much more likely in cells in which the axon originates from a basal dendrite rather than from the soma. High-resolution recordings in vitro and computer modeling indicate that these spikes are elicited by synaptic input to the axon-carrying dendrite and thus escape perisomatic inhibition. Pyramidal cells with somatic axon origin can be activated during ripple oscillations by blocking their somatic inhibition. The recruitment of neurons into active ensembles is thus determined by axonal morphological features.

  View details for DOI 10.1126/science.abj1861

  View details for PubMedID 36137045

• Myt1l haploinsufficiency leads to obesity and multifaceted behavioral alterations in mice. Molecular autism Wohr, M., Fong, W. M., Janas, J. A., Mall, M., Thome, C., Vangipuram, M., Meng, L., Sudhof, T. C., Wernig, M. 2022; 13 (1): 19

  Abstract

  BACKGROUND: The zinc finger domain containing transcription factor Myt1l is tightly associated with neuronal identity and is the only transcription factor known that is both neuron-specific and expressed in all neuronal subtypes. We identified Myt1l as a powerful reprogramming factor that, in combination with the proneural bHLH factor Ascl1, could induce neuronal fate in fibroblasts. Molecularly, we found it to repress many non-neuronal gene programs, explaining its supportive role to induce and safeguard neuronal identity in combination with proneural bHLH transcriptional activators. Moreover, human genetics studies found MYT1L mutations to cause intellectual disability and autism spectrum disorder often coupled with obesity.METHODS: Here, we generated and characterized Myt1l-deficient mice. A comprehensive, longitudinal behavioral phenotyping approach was applied.RESULTS: Myt1l was necessary for survival beyond 24h but not for overall histological brain organization. Myt1l heterozygous mice became increasingly overweight and exhibited multifaceted behavioral alterations. In mouse pups, Myt1l haploinsufficiency caused mild alterations in early socio-affective communication through ultrasonic vocalizations. In adulthood, Myt1l heterozygous mice displayed hyperactivity due to impaired habituation learning. Motor performance was reduced in Myt1l heterozygous mice despite intact motor learning, possibly due to muscular hypotonia. While anxiety-related behavior was reduced, acoustic startle reactivity was enhanced, in line with higher sensitivity to loud sound. Finally, Myt1l haploinsufficiency had a negative impact on contextual fear memory retrieval, while cued fear memory retrieval appeared to be intact.LIMITATIONS: In future studies, additional phenotypes might be identified and a detailed characterization of direct reciprocal social interaction behavior might help to reveal effects of Myt1l haploinsufficiency on social behavior in juvenile and adult mice.CONCLUSIONS: Behavioral alterations in Myt1l haploinsufficient mice recapitulate several clinical phenotypes observed in humans carrying heterozygous MYT1L mutations and thus serve as an informative model of the human MYT1L syndrome.

  View details for DOI 10.1186/s13229-022-00497-3

  View details for PubMedID 35538503