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Title: Investigating the role of the RNA binding protein HuR in skeletal development and disease
Author: Johnson, Kirsty Anne
ISNI:       0000 0004 7964 1969
Awarding Body: University of Liverpool
Current Institution: University of Liverpool
Date of Award: 2019
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Osteoarthritis is a complex multifactorial degenerative disease that is characterised by progressive loss of articular cartilage and inflammation of the synovium resulting pain and loss of mobility. HuR is a ubiquitously expressed RNA binding protein involved in the post-transcriptional regulation of target mRNAs and can reduce their rate of turnover. Previously published data suggests that HuR is spatially regulated within developing cartilage and is involved in the regulation of chondrocyte genes and osteoarthritis. Furthermore, knockout of HuR in mice at pre-implantation stage leads a skeletal dysplasia, among other phenotypes. This project aimed to determine whether HuR activity is important for maintaining cartilage and skeletal phenotype appropriately. An inducible, cartilage-specific HuR knockout mouse model and a non-inducible limb bud and mesenchyme-specific HuR knockout mouse model were generated utilising the Cre/LoxP system, were Cre expression is driven by an aggrecan promotor and a Prx1 enhancer, respectively. Using these novel transgenic mouse models of HuR knockout, the role of HuR in embryonic development, during osteoarthritis and in chondrocytes was characterised. Induced aggrecan-driven knockout of HuR leads to severe dysregulation of skeletal development during embryogenesis, resulting in a lack of mineralisation of axial components including the ribs and spine, and craniofacial structures. Similarly, Prx1-driven knockout of HuR during embryonic development leads to altered mineralisation of the skeleton, most strikingly in the developing limbs. This is similar in many respects to the phenotype observed following a broader knockout of HuR at an earlier developmental stage and suggests a role for HuR during endochondral ossification. In vitro assays using murine primary chondrocytes suggest that HuR may be required for the appropriate regulation of a number of known chondrocyte marker genes including Sox9, Runx2 and Mmp13, of which the latter two are known to be critically involved in the regulation of chondrocyte hypertrophy and endochondral ossification. The roles of RNA binding protein-mediated post transcriptional gene control is still not well understood in orthopaedic tissues. This study indicates that spatial and temporal mis-control of the protein HuR can lead to impaired skeletal mineralisation, suggesting that it performs an important function in chondrogenesis and/or osteogenesis.
Supervisor: Tew, Simon ; Bou-Gharios, G. Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral