Biology subjects

Somavarapu, S.

Publications and source records attributed to Somavarapu, S..

3 recordsLinked to original sources

bioRxiv2026

Time Course and Microcircuit Mechanisms of Primary Motor Cortex Dysfunction in Progressive Parkinsonism

Dysfunction of the primary motor cortex (M1) has long been implicated in the pathophysiology of Parkinsons disease (PD), mostly as a link by which abnormal basal ganglia and thalamic activities are translated into motor symptoms. However, emerging evidence suggests that M1 neurons also exhibit maladaptive changes in advanced parkinsonism. Here, using a progressive mouse model of nigrostriatal neurodegeneration (i.e., the MitoPark mice, MP), we found that M1 neurons develop age- and striatal dopamine-dependent synaptic and cellular adaptations as parkinsonism progresses. The optogenetic, electrophysiological, pharmacological, and CRISPR-mediated genetic studies demonstrated that impaired 5-GABAA receptor-mediated inhibition and excessive activation of NMDA receptors of M1 pyramidal neurons are key microcircu it mechanisms underlying cortical circuit remodeling during progressive striatal dopamine (DA) loss. Furthermore, we found that treatment with L-DOPA at early or late stages of parkinsonism can prevent or rescue, respectively, the synaptic and cellular adaptations in M1. Together, the present study demonstrates the time course and the underlying molecular and microcircuit mechanisms of cortical network dysfunction during the development of parkinsonism.

neuroscience↗

bioRxiv2026

Emergence of Task-Related Motor Cortical Dysfunction in Mice with Progressive Parkinsonism

There are substantial functional changes in the primary motor cortex (M1) in Parkinsons disease (PD). However, the temporal relationship between midbrain dopaminergic (DA) neurodegeneration, M1 circuit dysfunction, and Parkinsonian motor symptoms remains poorly understood. Using a genetic mouse model of progressive nigrostriatal DA degeneration ("MitoPark" mice), we determine the time course of M1 cellular dysfunction and skilled movement impairment as the midbrain DA neurons gradually degenerate. M1 pyramidal neuronal subtypes were identified using AAV-mediated retrograde labeling. During progressive DA loss, MitoPark mice developed gradually impaired performance in a reach-to-grasp single-food-pellet task. These impairments were detectable at a moderate motor stage of Parkinsonism. In vivo GCaMP6f imaging revealed that impaired skilled movement was associated with reduced cellular activity and movement responsiveness of M1 pyramidal neurons at a moderate motor stage of Parkinsonism. While both the corticospinal (CSp) and intratelencephalic (IT) neurons send glutamatergic inputs to the striatum, only the CSp neurons showed a selective and significant reduction in cellular activity and movement responsiveness during reaches. At the population level, we found that M1 pyramidal neurons include heterogeneous functional clusters with distinct temporal profiles in response to skilled movement. While movement encoding by different functional clusters is longitudinally stable in control mice, it degrades and diverges significantly in MitoPark mice. The impaired stability is further supported by a longitudinal analysis of individual neuronal activity related to movements. Together, these results provide novel insights into the emergence of M1 circuit pathophysiology at cellular and neural population levels during progressive Parkinsonism.

neuroscience↗

bioRxiv2020

High-content screening for rare respiratory diseases: readthrough therapy in primary ciliary dyskinesia

Development of therapeutic approaches for rare respiratory diseases is hampered by the lack of systems that allow medium-to-high-throughput screening of fully differentiated respiratory epithelium from affected patients. This is a particular problem for primary ciliary dyskinesia (PCD), a rare genetic disease caused by mutations in genes that adversely affect ciliary movement and consequently mucociliary transport. Primary cell culture of basal epithelial cells from nasal brush biopsies, followed by ciliated differentiation at air-liquid interface (ALI) has proven to be a useful tool in PCD diagnostics but the techniques broader utility, including in pre-clinical PCD research, has been limited by the number of basal cells that it is possible to expand from such biopsies. Here, we describe a high-content, imaging-based screening method, enabled by extensive expansion of PCD patient basal cells and their culture into differentiated human respiratory epithelium in miniaturised 96-well transwell format ALI cultures. Analyses of ciliary beat pattern, beat frequency and ultrastructure indicate that a range of different PCD defects are retained in these cultures. We perform a proof-of-principle personalized investigation in reduced generation of motile cilia (RGMC), a rare and very severe form of PCD, in this case caused by a homozygous nonsense mutation (c.441C>A; p.Cys147*) in the MCIDAS gene. The screening system allowed multiple drugs inducing translational readthrough to be evaluated alone or in combination with inhibitors of nonsense-mediated decay. Restoration of basal body formation in the patients nasal epithelial cells was seen in vitro, suggesting a novel avenue for drug evaluation and development in PCD. SummaryWe describe primary cell culture of nasal epithelial cells from patients with primary ciliary dyskinesia including differentiatiation of these to a ciliary phenotype and high-content screening in miniaturised air-liquid interface cultures.

cell biology↗