Biology subjects

Niehaus, M.

Publications and source records attributed to Niehaus, M..

4 recordsLinked to original sources

bioRxiv2026

Spinal V2a neurons support locomotor propagation via long-range connectivity

The spinal cord contains a diverse set of neurons whose activity is vital for motor control. Despite the importance of these spinal interneurons in network models of locomotion, their circuitry remains poorly understood. We quantified the synaptic output of V2a (vsx2+) interneurons, a glutamatergic population implicated in control of locomotor speed, rhythm generation, and recovery from injury, using the larval zebrafish. Surprisingly, we found that the majority of monosynaptic output from V2a neurons occurs onto motor and premotor targets at long ranges, in contrast to models that posit V2a neurons as the source of recurrent local excitation. Focal loss of V2a neurons impairs long-range propagation of locomotor output, but not local rhythm generation, in accordance with their long-range connectivity. Our results position V2a neurons as major mediators of locomotor propagation and long-range coordination in the spinal cord.

neuroscience↗

bioRxiv2025

Subcellular mass spectrometry imaging of lipids and nucleotides using transmission geometry ambient laser desorption and plasma ionisation

Demand for mass spectrometry imaging (MSI) technologies offering subcellular resolution for tissues and cell imaging is rapidly increasing. To accomplish this, efficient analyte ionisation is essential, given the small amounts of material sample in each pixel. Herein, we describe an atmospheric pressure transmission-geometry matrix-assisted laser desorption source equipped with plasma ionisation. By utilising a novel pre-staining method for sample preparation lipid signal intensities were enhanced by an order of magnitude compared to conventional matrix-only methods, while serendipitously enabling imaging of numerous nucleotides. The system enables detection of up to 200 lipids and nucleotides in tissues at 1 {micro}m-pixel size while informative MSI data is still obtained down to 250 nm pixel size. The use of sub-micron pixels is shown to discern subcellular features through combinations with fluorescence microscopy. This method provides a powerful tool for cellular and sub-cellular imaging of small molecules from tissues and cells for spatial biology applications.

cell biology↗

bioRxiv2024

Histology-Guided Single-Cell Mass Spectrometry Imaging using Integrated Bright-field and Fluorescence Microscopy

The rapidly evolving field of spatial biology revolves around the analysis of cells in their native microenvironment. This analysis can include morphological features, the presence of specific antigens or gene expression. To add another layer of information, recent methodological advances in matrix-assisted laser desorption ionization mass spectrometry imaging (MALDI-MSI) now enable the untargeted analysis of lipids and metabolites at subcellular resolution. The integration of MALDI-MSI at the single-cell level with established optical modalities, however, relies on an accurate yet intricate co-registration. Here, we describe the integration of bright-field and fluorescence microscopy into a prototype ion source of a state-of-the art MALDI-MSI instrument to obtain lipid and fluorescence microscopy-derived information from the same specimen, hence with intrinsic spatial correlation. We demonstrate the potential of the combined mass spectrometric and optical single-cell analysis on three examples. This includes the visualization of intracellular lipid distributions in macrophages, the introduction of pre-MALDI immunofluorescence staining on the example of murine cerebellum, and the heterogeneity of lipid profiles of tumor infiltrating neutrophils correlated to their individual microenvironments. Overall, the achieved tight correlation of single-cell lipid profiles with morphologic features and protein expression patterns constitutes a powerful resource for cell biology.

cell biology↗

bioRxiv2022

An inosine triphosphate pyrophosphatase safeguards nucleic acids from aberrant purine nucleotides and prevents a constitutive salicylic acid response

- In plants, inosine is enzymatically introduced in some tRNAs but not in other RNAs or DNA. Nonetheless, our data show that RNA and DNA from Arabidopsis thaliana contain (deoxy)inosine, probably derived from non-enzymatic adenosine deamination in nucleic acids and usage of (deoxy)inosine triphosphate (dITP and ITP) during nucleic acid synthesis. - We combined biochemical approaches, sample preparation and LC-MS, as well as RNA-Seq to characterize a plant INOSINE TRIPHOSPHATE PYROPHOSPHATASE (ITPA) from Arabidopsis thaliana, which is conserved in many organisms, and investigated the sources of deaminated purine nucleotides in plants. - ITPA dephosphorylates deaminated nucleoside di- and triphosphates to the respective monophosphates. ITPA loss-of-function causes inosine di- and triphosphate accumulation in vivo and an elevated (deoxy)inosine content in DNA and RNA, as well as salicylic acid (SA) accumulation, early senescence and upregulation of transcripts associated with immunity and senescence. Cadmium-induced oxidative stress leads to more ITP in the wildtype, and this effect is enhanced in itpa mutants, suggesting that ITP originates from ATP deamination. - ITPA is part of a molecular protection system, preventing accumulation of (d)ITP, its usage for nucleic acid synthesis, and probably nucleic acid stress leading to SA accumulation, stress gene induction and early senescence.

plant biology↗