Biology subjects

Kann, M.

Publications and source records attributed to Kann, M..

5 recordsLinked to original sources

bioRxiv2026

Behavioral state-dependent norepinephrine dynamics in the primary somatosensory and prefrontal cortices during tactile detection tasks

Animals must integrate sensory information, ignore behaviorally irrelevant stimuli, and respond to behaviorally relevant stimuli to find food, find mates, avoid predators, and ultimately survive. In mammals, these goal-directed behaviors require the coordinated activity of many brain regions, including sensory and prefrontal cortices and neuromodulatory brainstem nuclei like the locus coeruleus (LC), which is the brains primary source of norepinephrine (NE). NE release resulting from LC activity and arousal indexed by pupil size exert strong influences on goal-directed behavior. We explored the relationships between pupil size, cortical noradrenergic dynamics, and behavior in a tactile signal detection task. We monitored pupil dynamics and fluorescent GRABNE signals in somatosensory and medial prefrontal cortices simultaneously during task execution and found that pupil size and synchronization of GRABNE signals at baseline were strong predictors of whether animals chose to respond. Baseline and post-reward cortical GRABNE levels varied strongly with pupil-linked arousal. We also employed a generalized linear model - hidden Markov model (GLM-HMM) framework to identify distinct, stable behavioral states throughout the task that characterize task performance. We found distinct psychometric curves, task-related pupil dynamics, and cortical NE dynamics across these behavioral states. Significance StatementBehavioral state strongly shapes goal-directed behavior, which in turn depends on the coordinated activity of distributed brain regions, including the sensory and prefrontal cortices. By simultaneously measuring pupil size and cortical noradrenergic dynamics, and by identifying psychophysically distinct behavioral states during a tactile detection task, this study establishes links between pupil-linked arousal, norepinephrine signaling in somatosensory and prefrontal cortices, and trial outcomes. These findings provide new insight into how the locus coeruleus - norepinephrine system regulates perception and decision-making.

neuroscience↗

bioRxiv2025

Single-Cell Resolution of Cellular Damage Illuminates Disease Progression

Degenerative diseases feature progressive accumulation of cellular damage, leading to impaired organ function. Capturing such gradual decline of individual cells in vivo remains challenging. Here, we present a universal framework for quantifying damage at single-cell resolution, to uncover molecular trajectories of degeneration. This method enables the detection of progressive damage within cell populations under physiological and pathological conditions. We developed the Podocyte Damage Score (PDS) and Hepatocyte Damage Score (HDS) to monitor deterioration in kidney glomerulosclerosis and liver steatosis. The application of these scores to murine and human datasets quantified cellular damage across disease models and distinguished varying degrees of damage even in unperturbed samples. The PDS revealed circadian gene expression dysregulation as a consequence of podocyte injury, while the HDS identified a threshold of hepatocyte damage leading to senescence and metabolic dysfunction. The approach provides a scalable tool for decoding disease progression and identifying therapeutic targets across degenerative disorders.

bioinformatics↗

bioRxiv2020

DNA damage activates mTORC1 signaling in podocytes leading to glomerulosclerosis

DNA repair is essential for preserving genome integrity and ensuring cellular functionality and survival. Podocytes, post-mitotic glomerular epithelial cells, bear limited regenerative capacity, and their survival is indispensable to maintain the function of the kidneys filtration units. While podocyte depletion is a hallmark of the aging process and of many proteinuric kidney diseases, the underlying factors remain unclear. We investigated DNA repair in podocyte diseases by using a constitutive and an inducible podocyte-specific knockout mouse model for Ercc1, a multifunctional endonuclease cofactor involved in nucleotide excision repair (NER), interstrand crosslink (ICL) repair, and DNA double-strand break (DSB) repair. We assessed the consequences of Ercc1 loss in vivo, complemented by mechanistical in vitro studies of induced DNA damage in cultured podocytes. Furthermore, we characterized DNA damage-related alterations in mouse and human renal tissue of different ages as well as in patient biopsies with minimal change disease and focal segmental glomerulosclerosis. Podocyte-specific Ercc1 knockout resulted in accumulation of DNA damage with ensuing proteinuria, podocyte loss, glomerulosclerosis, renal insufficiency, and reduced lifespan. The response to genomic stress was different to the pattern reported in other cell types, as podocytes activated mTORC1 signaling upon DNA damage in vitro and in vivo. The induced mTORC1 activation was abrogated by inhibiting DNA damage response through DNA-PK and ATM kinases in vitro. Moreover, pharmacological inhibition of mTORC1 modulated the development of glomerulosclerosis in Ercc1-deficient mice. Perturbed DNA repair gene expression and genomic stress was also detected in podocytes of human focal segmental glomerulosclerosis, characterized by podocyte loss. Beyond that, DNA damage accumulation occurred in podocytes of healthy aging mice and humans. These findings reveal that genome maintenance is crucial for podocyte maintenance, linked to the mTORC1 pathway, and involved in the aging process as well as in the development of glomerulosclerosis, potentially serving as a therapeutic target in the future.

cell biology↗

bioRxiv2019

DomainScope: A Disease Network based on protein domain connections

Protein domains are highly conserved functional units of proteins. Because they carry functionally significant information, the majority of the coding disease variants are located on domains. Additionally, domains are specific units of the proteins that can be targeted for drug delivery purposes. Here, using information about variants sites associated with diseases, a disease network was built, based on their sharing the same domain and domain variation site. The result was 49,990 disease pairs linked by domain variant site and 533,687 disease pairs that share the same mutated domain. These pairs were compared to disease pairs made using previous methods such as gene identity and gene variant site identity, which revealed that over 8,000 of these pairs were not only missing from the gene pairings but also not found commonly together in literature. The disease network was analyzed from their disease subject categories, which when compared to the gene-based disease network revealed that the domain method results in higher number of connections across disease categories versus within a disease category. Further, a study into the drug repurposing possibilities of the disease network created using domain revealed that 16,902 of the disease pairs had a drug reported for one disease but not the other, highlighting the drug repurposing potential of this new methodology.

bioinformatics↗

bioRxiv2017

Individual nephron proteomes connect morphology and function in proteinuric kidney disease

In diseases of many parenchymatous organs, heterogenous detoriation of individual functional units determines the clinical prognosis. However, the molecular characterization of these subunits remains a technological challenge that needs to be addressed in order to better understand pathological mechanisms. Sclerotic and proteinuric glomerular kidney disease is a frequent and heterogeneous disease which affects a fraction of nephrons, glomeruli and draining tubules, to variable extents, and for which no treatment exists. Here, we developed and applied an antibody-independent methodology to investigate heterogeneity of individual nephron segment proteomes from mice with proteinuric kidney disease. This \"one-segment-one-proteome-approach\" defines mechanistic connections between upstream (glomerular) and downstream (tubular) nephron segment populations. In single glomeruli from two different mouse models of sclerotic glomerular disease, we identified a coherent protein expression module consisting of extracellular matrix protein deposition (reflecting glomerular sclerosis), glomerular albumin (reflecting proteinuria) and LAMP1, a lysosomal protein. This module was associated with a loss of podocyte marker proteins. In an attempt to target this protein co-expression module, genetic ablation of LAMP1-correlated lysosomal proteases in mice could ameliorate glomerular damage. Furthermore, individual glomeruli from patients with genetic sclerotic and non-sclerotic proteinuric diseases demonstrated increased abundance of lysosomal proteins, in combination with a decreased abundance of the mutated gene products. Therefore, increased glomerular lysosomal load is a conserved key mechanism in proteinuric kidney diseases, and the technology applied here can be implemented to address heterogeneous pathophysiology in a variety of diseases at a sub-biopsy scale

physiology↗