Category Archives: Publications

ARMET/MANF paper accepted for publication in Cell Stress and Chaperones

Musculoskeletal news, Publications

Mesencephalic astrocyte-derived neurotrophic factor is an important factor in chondrocyte ER homeostasis.

Bell PA, Dennis EP, Hartley CL, Jackson RM, Porter A, Boot-Handford RP, Pirog KA, Briggs MD.

Mesencephalic astrocyte-derived neurotrophic factor (MANF) is an endoplasmic reticulum (ER) resident protein that can be secreted due to an imperfect KDEL motif. MANF plays a cytoprotective role in several soft tissues and is upregulated in conditions resulting from intracellular retention of mutant protein, including two skeletal diseases, metaphyseal chondrodysplasia type Schmid (MCDS) and multiple epiphyseal dysplasia (MED).

The role of MANF in skeletal tissue homeostasis is currently unknown. Interestingly, cartilage-specific deletion of Manf in a mouse model of MED resulted in increased disease severity, suggesting its upregulation may be chondroprotective. Treatment of MED chondrocytes with exogenous MANF led to a decrease in the cellular levels of BiP (GRP78), confirming MANF’s potential to modulate ER stress responses. However, it did not alleviate the intracellular retention of mutant matrilin-3, suggesting that it is the intracellular MANF that is of importance in the pathobiology of skeletal dysplasias.

The Col2Cre-driven deletion of Manf from mouse cartilage resulted in a chondrodysplasia-like phenotype. Interestingly, ablation of MANF in cartilage did not have extracellular consequences, but led to an upregulation of several ER-resident chaperones including BiP. This apparent induction of ER-stress in turn led to dysregulated chondrocyte apoptosis and decreased proliferation, resulting in reduced long bone growth.

We have previously shown that ER stress is an underlying disease mechanism for several skeletal dysplasias. The cartilage-specific deletion of Manf described in this study phenocopies our previously published chondrodysplasia models, further confirming that ER-stress itself is sufficient to disrupt skeletal growth and thus represents a potential therapeutic target.

 

 

First paper of 2018 published!

Musculoskeletal news, Publications

Calcium activated nucleotidase 1 (CANT1) is critical for glycosaminoglycan biosynthesis in cartilage and endochondral ossification.

Paganini C, Monti L, Costantini R, Besio R, Lecci S, Biggiogera M, Tian K, Schwartz JM, Huber C, Cormier-Daire V, Gibson BG, Pirog KA, Forlino A, Rossi A.

Desbuquois dysplasia type 1 (DBQD1) is a chondrodysplasia caused by mutations in CANT1 gene encoding an ER/Golgi calcium activated nucleotidase 1 that hydrolyses UDP. Here, using Cant1 knock-in and knock-out mice recapitulating DBQD1 phenotype, we report that CANT1 plays a crucial role in cartilage proteoglycan synthesis and in endochondral ossification. Specifically, the glycosaminoglycan synthesis was decreased in chondrocytes from Cant1 knock-out mice and their hydrodynamic size was reduced, whilst the sulfation was increased and the overall proteoglycan secretion was delayed. Interestingly, knock-out chondrocytes had dilated ER cisternae suggesting delayed protein secretion and cellular stress; however, no canonical ER stress response was detected using microarray analysis, Xbp1 splicing and protein levels of BiP and ATF4. The observed proteoglycan defects caused deregulated chondrocyte proliferation and maturation in the growth plate resulting in the reduced skeletal growth. In conclusion, the pathogenic mechanism of DBQD1 comprises deregulated chondrocyte performance due to defective intracellular proteoglycan synthesis and altered proteoglycan properties in the extracellular matrix.

New therapeutic targets in rare genetic skeletal diseases – an Expert Opinion review

Publications

New Targets

Abstract

Introduction: Genetic skeletal diseases (GSDs) are a diverse and complex group of rare genetic conditions that affect the development and homeostasis of the skeleton. Although individually rare, as a group of related diseases, GSDs have an overall prevalence of at least 1 per 4,000 children. There are currently very few specific therapeutic interventions to prevent, halt or modify skeletal disease progression and therefore the generation of new and effective treatments requires novel and innovative research that can identify tractable therapeutic targets and biomarkers of these diseases.
Areas covered: Remarkable progress has been made in identifying the genetic basis of the majority of GSDs and in developing relevant model systems that have delivered new knowledge on disease mechanisms and are now starting to identify novel therapeutic targets. This review will provide an overview of disease mechanisms that are shared amongst groups of different GSDs and describe potential therapeutic approaches that are under investigation.
Expert opinion: The extensive clinical variability and genetic heterogeneity of GSDs renders this broad group of rare diseases a bench to bedside challenge. However, the evolving hypothesis that clinically different diseases might share common disease mechanisms is a powerful concept that will generate critical mass for the identification and validation of novel therapeutic targets and biomarkers.

Full text available from Journal website here

Or download a .pdf file here: review

Cartilage-Specific Ablation of XBP1 Signaling – research paper

Publications
 oarsiCartilage-Specific Ablation of XBP1 Signaling in Mouse Results in a Chondrodysplasia Characterised by Reduced Chondrocyte Proliferation and Delayed Cartilage Maturation and Mineralization

T.L. Cameron, I.L. Gresshoff, K.M. Bella, K.A. Piróg, L. Sampurno, C.L. Hartley, E.M. Sanford, R. Wilson, J. Ermann, R.P. Boot-Handford, L.H. Glimcher, M.D. Briggs, J.F. Bateman

Osteoarthritis Cartilage. 2015 Jan 16th

The full paper can be found here

Or download a .pdf file here: Xbp1 KO

Role of CHOP and genetic background in chondrodysplasia – research paper

Publications

plos-one-chop

Abstract

Pseudoachondroplasia (PSACH) is an autosomal dominant skeletal dysplasia caused by mutations in cartilage oligomericmatrix protein (COMP) and characterised by short limbed dwarfism and early onset osteoarthritis. Mouse models of PSACH show variable retention of mutant COMP in the ER of chondrocytes, however, in each case a different stress pathway is activated and the underlying disease mechanisms remain largely unknown. T585M COMP mutant mice are a model ofmoderate PSACH and demonstrate a mild ER stress response. Although mutant COMP is not retained in significantquantities within the ER of chondrocytes, both BiP and the pro-apoptotic ER stress-related transcription factor CHOP aremildly elevated, whilst bcl-2 levels are decreased, resulting in increased and spatially dysregulated chondrocyte apoptosis. To determine whether the abnormal chondrocyte apoptosis observed in the growth plate of mutant mice is CHOP-mediated, we bred T585M COMP mutant mice with CHOP-null mice to homozygosity, and analysed the resulting phenotype. Although abnormal apoptosis was alleviated in the resting zone following CHOP deletion, the mutant growth plates were generally more disorganised. Furthermore, the bone lengths of COMP mutant CHOP null mice were significantly shorter at 9 weeks of age when compared to the COMP mutant mice, including a significant difference in the skull length. Overall, these data demonstrate that CHOP-mediated apoptosis is an early event in the pathobiology of PSACH and suggest that the lack of CHOP, in conjunction with a COMP mutation, may lead to aggravation of the skeletal phenotype via a potentially synergistic effect on endochondral ossification.
You can download the full paper here: CHOP paper

Mild myopathy in mouse models of skeletal diseases – research paper

Publications

paper myo

Abstract

Pseudoachondroplasia (PSACH) and multiple epiphyseal dysplasia (MED) are skeletal disorders resulting from mutations in COMP, matrilin-3 or collagen IX and are characterised by short-limbed dwarfism and premature osteoarthritis. Interestingly, recent reports suggest patients can also manifest with muscle weakness. Here we present a detailed analysis of two mouse models of the PSACH/MED disease spectrum; ΔD469 T3-COMP (PSACH) and V194D matrilin-3 (MED). In grip test experiments T3-COMP mice were weaker than wild-type littermates, whereas V194D mice behaved as controls, confirming that short-limbed dwarfism alone does not contribute to PSACH/MED-related muscle weakness. Muscles from T3-COMP mice showed an increase in centronuclear fibers at the myotendinous junction. T3-COMP tendons became more lax in cyclic testing and showed thicker collagen fibers when compared with wild-type tissue; matrilin-3 mutant tissues were indistinguishable from controls. This comprehensive study of the myopathy associated with PSACH/MED mutations enables a better understanding of the disease progression, confirms that it is genotype specific and that the limb weakness originates from muscle and tendon pathology rather than short-limbed dwarfism itself. Since some patients are primarily diagnosed with neuromuscular symptoms, this study will facilitate better awareness of the differential diagnoses that might be associated with the PSACH/MED spectrum and subsequent care of PSACH/MED patients.

The full paper can be seen here

Or downloaded here: myopathy paper