Investigation of multiple-dynein transport of melanosomes by non-invasive force measurement using fluctuation unit χ

Number of kinesins engaged in axonal cargo transport: A novel biomarker for neurological disorders

Kinesin motor proteins play crucial roles in anterograde transport of cargo vesicles in neurons, moving them along axons from the cell body towards the synaptic region. Not only the transport force and velocity of single motor protein, but also the number of kinesin molecules involved in transporting a specific cargo, is pivotal for synapse formation. This collective transport by multiple kinesins ensures stable and efficient cargo transport in neurons. Abnormal increases or decreases in the number of engaged kinesin molecules per cargo could potentially act as biomarkers for neurodegenerative diseases such as Alzheimer's, Parkinson's, amyotrophic lateral sclerosis (ALS), spastic paraplegia, polydactyly syndrome, and virus transport disorders. We review here a model constructed using physical measurements to quantify the number of kinesin molecules associated with their cargo, which could shed light on the molecular mechanisms of neurodegenerative diseases related to axonal transport.

Cell Junction and Vesicle Trafficking-Mediated Melanosome/Melanin Transfer Are Involved in the Dynamic Transformation of Goldfish Carassius auratus Skin Color

Goldfish are one of the most popular models for studying the genetic diversity of skin color. Transcriptome sequencing (RNA-seq) and whole genome bisulfate sequencing (WGBS) of skin tissues from the third filial (F3) cyan (CN), black (BK), and white (WH) goldfish were conducted to analyze the molecular mechanism of color transformation in fish. The RNA-seq yielded 56 Gb of clean data and 56,627 transcripts from nine skin samples. The DEGs (differentially expressed genes) were enriched in cell junction cellular components and the tight junction pathway. Ninety-five homologs of the claudin family were predicted and 16 claudins were identified in correlation with skin color transformation. WGBS yielded 1079 Gb of clean data from 15 samples. Both the DEGs and the DMRs (differentially methylated regions) in the BK_CN group were found to be enriched in cytoskeleton reorganization and vesicle trafficking. Masson staining and TEM (transmission electron microscopy) confirmed the varied distribution and processes of melanosome/melanin in skin tissues. Our results suggested that cytoskeleton reorganization, cell junction, and the vesicle trafficking system played key roles in the transfer of the melanosome/melanin, and it was the extracellular translocation rather than the biosynthesis or metabolism of the melanin process that resulted in the color transformation of cyan goldfish. The data will facilitate the understanding of the molecular mechanisms underlying dynamic skin color transformation in goldfish.

Effective Langevin equations leading to large deviation function of time-averaged velocity for a nonequilibrium Rayleigh piston

We study fluctuating dynamics of a freely movable piston that separates an infinite cylinder into two regions filled with ideal gas particles at the same pressure but different temperatures. To investigate statistical properties of the time-averaged velocity of the piston in the long-time limit, we perturbatively calculate the large deviation function of the time-averaged velocity. Then, we derive an infinite number of effective Langevin equations yielding the same large deviation function as in the original model. Finally, we provide two possibilities for uniquely determining the form of the effective model.

Effects of dynein inhibitor on the number of motor proteins transporting synaptic cargos

Synaptic cargo transport by kinesin and dynein in hippocampal neurons was investigated by noninvasively measuring the transport force based on nonequilibrium statistical mechanics. Although direct physical measurements such as force measurement using optical tweezers are difficult in an intracellular environment, the noninvasive estimations enabled enumerating force-producing units (FPUs) carrying a cargo comprising the motor proteins generating force. The number of FPUs served as a barometer for stable and long-distance transport by multiple motors, which was then used to quantify the extent of damage to axonal transport by dynarrestin, a dynein inhibitor. We found that dynarrestin decreased the FPU for retrograde transport more than for anterograde transport. This result indicates the applicability of the noninvasive force measurements. In the future, these measurements may be used to quantify damage to axonal transport resulting from neuronal diseases, including Alzheimer's, Parkinson's, and Huntington's diseases.

Physical parameters describing neuronal cargo transport by kinesin UNC-104

In this review, we focus on the kinesin-3 family molecular motor protein UNC-104 and its regulatory protein ARL-8. UNC-104, originally identified in Caenorhabditis elegans (C. elegans), has a primary role transporting synaptic vesicle precursors (SVPs). Although in vitro single-molecule experiments have been performed to primarily investigate the kinesin motor domain, these have not addressed the in vivo reality of the existence of regulatory proteins, such as ARL-8, that control kinesin attachment to/detachment from cargo vesicles, which is essential to the overall transport efficiency of cargo vesicles. To quantitatively understand the role of the regulatory protein, we review the in vivo physical parameters of UNC-104-mediated SVP transport, including force, velocity, run length and run time, derived from wild-type and arl-8-deletion mutant C. elegans. Our future aim is to facilitate the construction of a consensus physical model to connect SVP transport with pathologies related to deficient synapse construction caused by the deficient UNC-104 regulation. We hope that the physical parameters of SVP transport summarized in this review become a useful guide for the development of such model.