Biology subjects

Paric, E.

Publications and source records attributed to Paric, E..

3 recordsLinked to original sources

bioRxiv2025

Fluorescence recovery after photobleaching reveals different 1 behaviour2 of tropomyosin isoforms Tpm3.1 and Tpm4.2 in dendritic spines

Actin is the predominant cytoskeletal structure in both the pre- and the post-synaptic compartment of excitatory synapses in the brain, which are formed between the distal part of the axon and the distal site of dendritic spines. Tropomyosin (Tpm) is regarded a master regulator of actin dynamics in mammalian cells. Tpm isoforms, found in neurons are encoded by the Tpm1, Tpm3 and Tpm4 genes, and have a distinct temporal and spatial distribution of expression. Tpm3 and Tpm4 gene products have been found to segregate to the postsynaptic region of central nervous system synapses. Functional differences between Tpm3.1 and Tpm4.2 in neurons have been reported in previous studies. However, these were lacking a detailed analysis of the molecular mobility and dynamics of these two Tpm isoforms in the dendritic compartment. Here, we investigated the kinetic properties of Tpm3.1 and Tpm4.2 via a Fluorescent Recovery After Photobleaching (FRAP) approach and have discovered that Tpm3.1 and Tpm4.2 have distinct kinetic features in dendritic spines. Moreover, we investigated the dynamics of actin in the presence of either Tpm3.1 or Tpm4.2 isoform overexpression, using F-tractin as a reporter of filamentous actin. We have shown that the kinetics of actin turnover is significantly different in response to Tpm3.1 overexpression when compared the actin turnover in response to Tpm4.2 overexpression. Our study further elucidates the roles of Tpm3.1 and Tpm4.2 and provides important conclusions for future studies that are focused on discerning the molecular pathways of Tpm3.1 and Tpm4.2 segregation into different neuronal compartments.

cell biology↗

bioRxiv2025

Mitochondrial dysfunction in Machado Joseph disease: insights from a multi-model system

Spinocerebellar ataxia type-3 (SCA3), also known as Machado Joseph disease, MJD) is a fatal, neurodegenerative disease belonging to the polyglutamine repeat disease family, caused by inheritance of an abnormal form of the ATXN3 gene, carrying a longer than usual trinucleotide repeat sequence. Within this study we explored mitochondrial function in a range of different experimental models of MJD, including transgenic zebrafish, mice and neuronal cells, to gain an understanding of mitochondrial function in the disease, and possible mechanisms of any dysfunction. Firstly, we examined the transgenic CMVMJD135 mouse model that develops impaired movement, neurodegeneration and decreased survival. We performed proteomic analysis on brain lysates extracted from a cohort of male and female WT and MJD mice, for analysis of differences in male and female mice separately. We identified that a major difference predicted by Ingenuity Pathway Analysis to be in both male and female MJD mice was related to impaired oxidative phosphorylation and mitochondrial dysfunction. We examined primary neuron cultures obtained from CMVMJD135 mice, validating the findings of the proteomic analysis, and finding changes to mitochondrial morphology, as well. We further examined a transgenic zebrafish model of MJD that expresses EGFP fused human ataxin-3 with short or long polyQ stretches (23 or 84Q, respectively) in neurons (expression driven under the elav/HuC promoter). The MJD zebrafish also exhibit altered mitochondrial electron transport chain complex protein levels, together with enhanced sensitivity to rotenone administration, which may be a valuable readout for treatment investigation studies in the future. Together, this study confirms, and extends on, the growing body of evidence suggesting that mitochondrial dysfunction plays a role in MJD, warranting investigation for therapeutic intervention.

neuroscience↗

bioRxiv2025

Knock-out of Tpm4.2/actin filaments alters neuronal signaling, neurite outgrowth and behavioral phenotypes in mice.

Tropomyosins (Tpm) are master regulators of actin dynamics through forming co-polymers with filamentous actin. Despite the well-understood function of muscle Tpms in the contractile apparatus of muscle cells, much less is known about the diverse physiological function of cytoplasmic Tpms in eukaryotic cells. Here, we investigated the role of the Tpm4.2 isoform in neuronal processes including signaling, neurite outgrowth and receptor recycling using primary neurons from Tpm4.2 knock-out mice. Live imaging of calcium and electro-physiology data demonstrated increased frequency, yet reduced strength of single neuron spikes. Calcium imaging further showed increase in neuronal networks. In vitro assays of Tpm4.2 knock-out neurons displayed impaired recycling of the AMPA neurotransmitter receptor subunit GluA1. Morphometric analysis of neurite growth showed increased dendritic complexity and altered dendritic spine morphology in Tpm4.2 knock-out primary neurons. Behavioral analysis of Tpm4.2 knock-out mice displayed heightened anxiety in Open field test whilst Elevated Plus maze displayed heightened anxiety only in females. A sex-dependent phenotype was also seen in the Social Preference test with impaired social memory and socialization in female Tpm4.2 knock-out mice, whilst male and female knock-out mice had impaired recognition memory in a Novel Object Recognition test. Our study depicts the multi-faceted role of the Tpm4.2 isoform and its co-polymer F-actin population in neurons, with potential implications for better understanding diseases of the nervous system which involve actin cytoskeleton dys-function.

neuroscience↗