Biology subjects

Ai, M.

Publications and source records attributed to Ai, M..

3 recordsLinked to original sources

bioRxiv2023

Spliceosomal mutations decouple 3' splice site fidelity from cellular fitness

The fidelity of splice site selection is thought to be critical for proper gene expression and cellular fitness. In particular, proper recognition of 3'-splice site (3'SS) sequences by the spliceosome is a daunting task considering the low complexity of the 3'SS consensus sequence YAG. Here we show that inactivating the near-essential splicing factor Prp18p results in a global activation of alternative 3'SS, many of which harbor sequences that highly diverge from the YAG consensus, including some highly unusual non-AG 3'SS. We show that the role of Prp18p in 3'SS fidelity is promoted by physical interactions with the essential splicing factors Slu7p and Prp8p and synergized by the proofreading activity of the Prp22p helicase. Strikingly, structure-guided point mutations that disrupt Prp18p-Slu7p and Prp18p-Prp8p interactions mimic the loss of 3'SS fidelity without any impact on cellular growth, suggesting that accumulation of incorrectly spliced transcripts does not have a major deleterious effect on cellular viability. These results show that spliceosomes exhibit remarkably relaxed fidelity in the absence of Prp18p, and that new 3'SS sampling can be achieved genome-wide without a major negative impact on cellular fitness, a feature that could be used during evolution to explore new productive alternative splice sites.

molecular biology↗

bioRxiv2022

Human mesenchymal stem cells and derived extracellular vesicles reduce sensory neuron hyperexcitability and pain-related behaviors in a mouse model of osteoarthritis

Osteoarthritis (OA) is a common degenerative joint disease characterized by joint pain and stiffness. In humans, mesenchymal stem cells (MSCs) and derived extracellular vesicles (MSC-EVs) have been reported to alleviate pain in knee OA. Here, we used the destabilization of the medial meniscus (DMM) mouse model of OA to investigate mechanisms by which MSCs and MSC-EVs influence pain-related behavior. We found that MSC and MSC-EV treated DMM mice displayed improved OA pain-related behavior (i.e. locomotion, digging and sleep) compared to untreated DMM mice. Improved behavior was not the result of reduced joint damage, but rather knee-innervating sensory neurons from MSC and MSC-EV treated mice did not display the hyperexcitability observed in untreated DMM mice. Furthermore, we found that MSC-EVs normalize sensory neuron hyperexcitability induced by nerve growth factor in vitro. Our study suggests that MSCs and MSC-EVs may reduce pain in OA by direct action on peripheral sensory neurons. TeaserMesenchymal stem cells and secreted extracellular vesicles normalize sensory neuron excitability to reduce pain.

neuroscience↗

bioRxiv2021

Functional characterization of ovine dorsal root ganglion neurons reveals peripheral sensitization after osteochondral defect

ObjectiveKnee joint trauma can cause an osteochondral defect (OD), a risk factor for osteoarthritis and cause of debilitating pain in patients. Modelling OD in rodents is difficult due to their smaller joint size. This study proposes sheep as a translationally relevant model to understand the neuronal basis of OD pain. MethodsUnilateral 6 mm deep OD was induced in adult sheep, 2-6 weeks after which dorsal root ganglion neurons (DRG neurons) were cultured from the control and OD side. Functional assessment of neuronal excitability and activity of the pain-related ion channels, TRPV1 and P2X3, was carried out using electrophysiology and Ca2+-imaging. Immunohistochemistry was utilized to verify expression of pain-related proteins. ResultsAn increased proportion of OD DRG neurons (sheep, n = 3, Ctrl neurons, n =15, OD neurons, n = 16) showed spontaneous electrical excitability (p = 0.009, unpaired t-test) and hyperexcitability upon TRPV1 agonist (capsaicin) application (p = 0.04, chi-sq test). Capsaicin also produced Ca2+ influx in an increased proportion of OD DRG neurons isolated (p = 0.001, chi-sq test). By contrast, neither protein expression, nor functionality of the P2X3 ion channel were altered in OD neurons. ConclusionsWe provide evidence of increased excitability of DRG neurons (which is an important neural correlate of pain) and TRPV1 function in an OD sheep model. Our data show that functional assessment of sheep DRG neurons can provide important insights into the neural basis of OD pain and thus potentially prevent its progression into arthritic pain.

neuroscience↗