Biology subjects

Young, C. J.

Publications and source records attributed to Young, C. J..

4 recordsLinked to original sources

bioRxiv2023

Reduced glycolysis links resting zone chondrocyte proliferation in the growth plate

A gain-of-function mutation of the chondrocyte-specific microRNA, miR-140-5p, encoded by the MIR140 gene, causes spondyloepiphyseal dysplasia, Nishimura type (SEDN, also known as SED, MIR140 type; MIM, 611894). We reported that a mouse model for SEDN showed a unique growth plate phenotype that is characterized by an expansion of the resting zone of the growth plate and an increase in resting chondrocytes, of which the mechanism of regulation is poorly understood. We found that the miR-140 mutant chondrocytes showed a significant reduction of Hif1a, the master transcription factor that regulates energy metabolism in response to hypoxia. Based on this finding, we hypothesized that energy metabolism plays a regulatory role in resting chondrocyte proliferation and growth plate development. In this study, we show that suppression of glycolysis via LDH ablation causes an expansion of the resting zone and skeletal developmental defects. We have also found that reduced glycolysis results in reduced histone acetylation in the miR-140 mutant as well as LDH-deficient chondrocytes likely due to the reduction in acetyl-CoA generated from mitochondria-derived citrate. Reduction in acetyl-CoA conversion from citrate by deleting Acly caused an expansion of the resting zone and a similar gross phenotype to LDH-deficient bones without inducing energy deficiency, suggesting that the reduced acetyl-CoA, but not the ATP synthesis deficit, is responsible for the increase in resting zone chondrocytes. Comparison of the transcriptome between LDH-deficient and Acly-deficient chondrocytes also showed overlapping changes including upregulation in Fgfr3. We also confirmed that overexpression of an activation mutation of Ffgr3 causes an expansion of resting zone chondrocytes. These data demonstrate the association between reduced glycolysis and an expansion of the resting zone and suggest that it is caused by acetyl-CoA deficiency, but not energy deficiency, possibly through epigenetic upregulation of FGFR3 signaling.

developmental biology↗

bioRxiv2022

Limited roles of Piezo mechanosensing channels in articular cartilage development and osteoarthritis progression

Osteoarthritis (OA) is a prevalent disease characterized by degeneration of the joint and pain. Mechanical stress plays a central role in OA development. It is hypothesized that cells in the OA joints produce OA-promoting molecules upon mechanical stress, and therefore, the mechanosensing systems are a theoretical target for OA treatment. Piezo mechanosensing channels mediate high-level mechanical stress in chondrocytes and have been suggested to play an important role during OA progression. To test this hypothesis, we ablated Piezo1 and Piezo2 in joint tissues using Gdf5-Cre transgenic mice [Piezo1 and 2 doubly conditional knockout (cKO) mice, cKO mice]. cKO mice showed normal development of knee joints. Both control and cKO mice developed modest to severe OA 12 weeks after the induction of OA, although some cKO mice showed milder OA. We did not find significant differences in pain in mice or gene expression after fluid flow stress in primary cells between control and cKO. Our data demonstrate the limited role of Piezo channels in joint development and OA progression. SummaryO_ST_ABSObjectiveC_ST_ABSTo investigate the role of Piezo1 and Piezo 2 in surgically induced osteoarthritis (OA) in mice. DesignMale conditional knockout (cKO) mice missing Piezo1 and Piezo2 in the joint via Gdf5-Cre transgenic mice were induced post-traumatic osteoarthritis (OA) by destabilization of the medial meniscus (DMM) of the right knee joint at 12 weeks of age. The severity of OA was assessed at 24 weeks of age using a modified Osteoarthritis Research Society International (OARSI) scoring system. OA-associated pain was evaluated by static weight bearing analysis at 4, 8, and 12 weeks post-operation. Additionally, articular chondrocytes isolated from cKO mice were exposed to fluid flow shear stress (FFSS) to evaluate the expression of OA-associated genes. ResultsMice with conditional deletion of Piezo1 and Piezo 2 showed normal joint development with no overt histological changes in the knee joint at 12 weeks and 24 weeks. DMM surgery induced moderate to severe OA in both control and cKO mice, although a few cKO mice showed milder OA. Pain assessment by static weight-bearing analysis suggested Piezo ablation in the joint has no beneficial effects on pain. FFSS increased the expression of OA-related genes both in control and cKO mice to similar extents. ConclusionPiezo1 and Piezo2 are not essential for normal joint development. Genetic ablation of Piezo channels did not confer evident protective effects on OA progression in mice. In vitro data suggests that different mechanotransducers other than Piezo channels mediate FFSS in mechanical stress-induced gene expression.

pathology↗

bioRxiv2022

Distributional coding of associative learning within projection-defined populations of midbrain dopamine neurons

Midbrain dopamine neurons are thought to play key roles in learning by conveying the difference between expected and actual outcomes. While this teaching signal is often considered to be uniform, recent evidence instead supports diversity in dopamine signaling. However, it remains poorly understood how heterogeneous signals might be organized to facilitate the role of downstream circuits mediating distinct aspects of behavior. Here we investigated the organizational logic of dopaminergic signaling by recording and labeling individual midbrain dopamine neurons during associative behavior. We defined combinations of protein expression and cellular localization to sort recorded neurons according to the striatal regions they innervate. Our findings show that reward information and task variables are not only heterogeneously encoded, with multiplexing, but also differentially distributed across populations of dopamine neurons projecting to different regions of striatum. These data, supported by computational modelling, indicate that such distributional coding can maximize dynamic range and tailor dopamine signals to facilitate the specialized roles of different striatal regions.

neuroscience↗

bioRxiv2021

Reversing the miRNA -5p/-3p stoichiometry reveals physiological roles and targets of miR-140 miRNAs

The chondrocyte specific miR-140 miRNAs are necessary for normal endochondral bone growth in mice. miR-140 deficiency causes dwarfism and craniofacial deformity. However, the physiologically important targets of miR-140 miRNAs are still unclear. The miR-140 gene (Mir140) encodes three chondrocyte-specific microRNAs, miR-140-5p, derived from the 5 strand of primary miR-140, and miR140-3p.1 and -3p.2, derived from the 3 strand of primary miR-140. miR-140-3p miRNAs are ten times more abundant than miR-140-5p likely due to the non-preferential loading of miR-140-5p to Argonaute proteins. To differentiate the role of miR-140-5p and -3p miRNAs in endochondral bone development, two distinct mouse models, miR140-C>T, in which the first nucleotide of miR-140-5p was altered from cytosine to uridine, and miR140-CG, where the first two nucleotides of miR-140-3p were changed to cytosine and guanine, were created. These changes are expected to alter Argonaute protein loading preference of -5p and -3p to increase -5p loading and decrease -3p loading without changing the function of miR140-5p. These models presented a mild delay in epiphyseal development with delayed chondrocyte maturation. Using RNA-sequencing analysis of the two models, direct targets of miR140-5p, including Wnt11, were identified. Disruption of the predicted miR140-5p binding site in the 3 untranslated region of Wnt11 was shown to increase Wnt11 mRNA expression and caused a modest acceleration of epiphyseal development. These results show that the relative abundance of miRNA-5p and -3p can be altered by changing the first nucleotide of miRNAs in vivo, and this method can be useful to identify physiologically important miRNA targets.

genetics↗