Biology subjects

Morris, C. J.

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

3 recordsLinked to original sources

bioRxiv2023

Structural Insights into Regulation of Insulin Expression Involving i-Motif DNA Structures in the Insulin-Linked Polymorphic Region.

The insulin linked polymorphic region (ILPR) is a variable number of tandem repeats (VNTR) region of DNA in the promoter of the insulin gene that regulates transcription of insulin. This region is known to form the alternative DNA structures, i-motifs and G-quadruplexes. Individuals have different sequence variants of VNTR repeats and although previous work investigated the effects of some variants on G-quadruplex formation, there is not a clear picture of the relationship between the sequence diversity, the DNA structures formed, and the functional effects on insulin gene expression. Here we show that different sequence variants of the ILPR form different DNA secondary structures and insulin expression is dependent on formation of i-motif and G-quadruplex structures. The first crystal structure and dynamics of an intramolecular i-motif also reveal sequences within the loop regions forming additional stabilising interactions, which are critical to formation of the stable i-motif structures that modulate insulin expression. The outcomes of this work reveal the detail in formation of stable i-motif DNA structures, with potential for rational based drug design for compounds to alter insulin gene expression.

biophysics↗

bioRxiv2022

Modeling Mechanical Feedback Mechanisms in a Multiscale Sliding Filament Model of Lymphatic Muscle Pumping

The lymphatic system maintains bodily fluid balance by returning interstitial fluid to the venous system. Flow can occur through a combination of extrinsic pumping, due to forces from surrounding tissues, and intrinsic pumping involving contractions of muscle in the lymphatic vessel walls. Lymph transport is important not only for fluid homeostasis, but also for immune function, as lymph is a carrier for immune cells. Lymphatic muscle cells exhibit cardiac-like phasic contractions to generate flow and smooth-muscle-like tonic contractions to regulate flow. Lymphatic vessels therefore act as both active pumps and conduits. Lymphatic vessels are sensitive to mechanical stimuli, including flow-induced shear stresses and pressure-induced vessel stretch. These forces modulate biochemical pathways, leading to changes in intracellular calcium and interaction with regulatory and contractile proteins. In a multiscale computational model of phasic and tonic contractions in lymphatic muscle coupled to a lumped-parameter model of lymphatic pumping, we tested different models of the mechanical feedback mechanisms exhibited by lymphatics in experiments. Models were validated using flow and pressure experiments not used in the models construction. The final model shows that with flow-induced shear stress modulation, there is a small change in flow rate but an increase in muscle efficiency. A better understanding of the mechanobiology of lymphatic contractions can help guide future lymphatic vessel experiments, providing a basis for developing better treatments for lymphatic dysfunction.

bioengineering↗

bioRxiv2022

A hydrogel-based model of aortic stiffness reveals that microtubules are novel regulators of smooth muscle cell hypertrophy

During ageing, the extracellular matrix of the aortic wall becomes more rigid. In response, VSMCs generate enhanced contractile forces. Our previous findings demonstrate that VSMC volume is enhanced in response to increased matrix rigidity, but our understanding of mechanisms regulating this process remain incomplete. In this current study, we show that microtubule stability in VSMCs is reduced in response to enhanced matrix rigidity via piezo1-mediated Ca2+ influx. Moreover, VSMC volume and Ca2+ flux was regulated by microtubule dynamics; microtubule stabilising agents reduced both VSMC volume and Ca2+ flux on rigid hydrogels, whereas microtubule destabilising agents increased VSMC volume and Ca2+ flux on pliable hydrogels. Finally, we show that disruption of the microtubule deacetylase HDAC6 uncoupled these processes and increased K40 alpha tubulin acetylation, VSMC volume and Ca2+ flux on pliable hydrogels, but did not alter VSMC microtubule stability. These findings uncover a microtubule stability switch that controls VSMC volume by regulating Ca2+ flux. Together, these data demonstrate that manipulation of microtubule stability can modify VSMC matrix rigidity response.

cell biology↗