Use this URL to cite or link to this record in EThOS:
Title: The role of Nuclear Lamins in regulating the circadian molecular clockwork : daily oscillations and response to mechanical stimulation
Author: Roskell, Clare Amy
ISNI:       0000 0004 7964 2347
Awarding Body: University of Liverpool
Current Institution: University of Liverpool
Date of Award: 2019
Availability of Full Text:
Access from EThOS:
Access from Institution:
Circadian rhythms are evolutionarily conserved ~24h biological cycles in physiology, metabolism, and behaviour, including locomotor activity. Musculoskeletal cells contain cell-autonomous, self-sustainable circadian clocks; synchronised by a central clock located in the suprachiasmatic nuclei. The nuclear lamina underlies the nuclear envelope and consists of type-V intermediate filament proteins called lamins. Laminopathies are a spectrum of clinical diseases with a mutation in Lmna, often including tissue-specific pathogenesis; musculoskeletal pathology is characterised by muscle wasting and cardiac defects. Lamin A is an important regulator of genome organisation, nuclear support and tethering of transcription factors, such as those involved in differentiation and stress response signalling pathways. Accordingly, in musculoskeletal cells, lamin A is crucial for acute responses to mechanical stimulation. The aims of this thesis investigated whether the molecular clock and lamin A bi-directionally regulate one another in musculoskeletal cells, and whether the circadian clock is responsive to mechanical stimuli, and then constructed a mathematical model to begin elucidating potential mechanisms of regulation. To determine whether lamin A oscillates with a circadian rhythm, circadian time-courses were collected from C2C12 myoblasts and myotubes, primary myotubes, and mouse muscle samples. Lamin A circadian oscillations were identified in mRNA, protein, and immunocytochemistry time-course data. To determine whether lamin A exerts feedback regulation on the circadian clock, lamin A was manipulated in musculoskeletal cells, and had a direct effect on core clock gene expression. siRNA knockdown of lamin A significantly decreased the expression of the core clock genes Per1, Per2, Bmal1, and Cry1; overexpression of lamin A increased the expression of core clock genes Per1, Per2, and Bmal1, and decreased the expression of Cry1. Furthermore, in response to in vitro strain by the Flexcell system, primary myoblasts and C2C12 myotubes demonstrated a decrease in Cry1 expression, and an increase in Cry1 and Bmal1 expression, respectively. Additionally, Clock gene expression was upregulated in Gastrocnemius and Quadricep muscle from mice subject to acute and chronic in vivo loading, respectively. Finally, 4 mathematical models were generated to investigate potential regulatory feedback pathways that may link the circadian clock and lamin A. These results revealed that lamin A oscillates with a circadian rhythm in musculoskeletal tissues, that the circadian clock is disrupted in response to lamin A knockdown and overexpression, and that the circadian clock is responsive to mechanical strain. Future studies may include deciphering whether this mechanism conveys mechanical stimulation and myogenic differentiation signals to the clock, and determining if the musculoskeletal clock is disrupted in laminopathy patients. Knowledge of the circadian clock and lamin A regulatory mechanisms can direct therapeutic strategies to reset altered clocks in patients with musculoskeletal disorders.
Supervisor: Tew, Simon ; Clegg, peter ; Pekovic-Vaughan, vanja Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral