Searchable abstracts of presentations at key conferences on calcified tissues

ba0001pp493 | Other diseases of bone and mineral metabolism | ECTS2013

Functional assessment of Paget's disease-causing mutations in sequestosome-1 (SQSTM1)

Azzam Eman , Helfrich Miep , Hocking Lynne

Abstract: Paget’s disease of bone (PDB) is characterised by focal lesions of local bone turnover driven by overactive osteoclasts, which often contain nuclear and cytoplasmic inclusion bodies. Mutations affecting the sequestosome-1 (SQSTM1) ubiquitin-associated (UBA) domain have been identified in individuals with PDB. SQSTM1, also known as p62, is a ubiquitously-expressed scaffold protein of 62 kDa that functions in multiple signalling pathways important for cell surviva...

ba0003pp161 | Cell biology: osteoclasts and bone resorption | ECTS2014

Ultrastructural imaging of the osteoclast secretory machinery in 3 dimensions

Helfrich Miep , Wilkinson Debbie , Mackenzie Kevin , Greenhorn John , Coxon Fraser

Osteoclasts secrete acid and cathepsin K to dissolve the mineral and digest the organic matrix of bone, cartilage and dentine. The secretions are by necessity destructive and potentially harmful to the cell itself and are therefore trafficked through the cell in membrane bound vesicles. Secretion takes place over a specialised membrane compartment, the ruffled border, which is only present in resorbing osteoclasts. The ruffled border membrane and the vesicles in its vicinity h...

ba0003pp370 | Other diseases of bone and mineral metabolism | ECTS2014

Isoform-specific effects of Sequestosome-1 UBA domain mutations on NF-κB signalling

Willems Ariane , Azzam Eman , Helfrich Miep , Hocking Lynne

Paget’s disease of Bone (PDB) is caused by mutations in the gene encoding Sequestosome-1 (Q17STM1 or p62) that affect the C-terminal Ubiquitin-Associated (UBA) domain. A second isoform of Q17STM1 exists (referred to hereafter as 55kDa-Q17STM1), which lacks the N-terminal Phox and Bem1 (PB1) domain and has previously been reported to be ~45x more abundant than Q17STM1/p62 in osteoclasts. Mutations in the UBA domain will also occur in this isoform. Several of the UBA mutati...

ba0005p190 | Cell biology: osteoclasts and bone resorption | ECTS2016

Identification and characterisation of vesicles in resorbing osteoclasts using electron tomography

McDermott Emma , Sunderhauf David , Mackenzie Kevin , Wilkinson Debbie , Helfrich Miep

Osteoclasts are the only cell type capable of resorption of mineralised matrix such as bone or dentine. Resorbing osteoclasts form distinct membrane domains: the functional secretory, the basolateral and the ruffled border (RB) domains. The RB allows acidification of the resorption lacuna, exocytosis of osteolytic enzymes and uptake of degraded bone material, processes that require directed vesicular transport. Few studies have tried to classify the vesicles near the RB into s...

ba0001pp211 | Cell biology: osteoblasts and bone formation | ECTS2013

Rab27a is involved in bone formation by osteoblasts

Coxon Fraser , Douglass Angela , Hughes Alun , Helfrich Miep , Seabra Miguel , Tolmachova Tanya

The Rab family GTPases Rab27a and Rab27b play an important role in the trafficking of lysosome-related organelles in specialised cells, such as melanocytes. Since secretory lysosomes, also considered a lysosome-related organelle, are important for osteoclast and osteoblast function, we hypothesised that Rab27 plays a role in bone physiology. In support of this, a recent study demonstrated impaired transport of RANK ligand to the plasma membrane in osteoblasts from mice lacking...

ba0001pp497 | Other diseases of bone and mineral metabolism | ECTS2013

A frameshift mutation in receptor activator of NF-κB reveals a potential ligand-independent mechanism for NF-κB activation

Dignan Cahal , Mellis David , Duthie Angela , Pangrazio Alessandra , Sobacchi Cristina , Schulz Ansgar , Helfrich Miep , Crockett Julie

Osteoclast-poor autosomal recessive osteopetrosis is characterised by susceptibility to fracture despite high bone mineral density as a consequence of an absence of osteoclasts. One of the 12 receptor activator of NF-κB (RANK) mutations associated with this condition is a frameshift mutation encoding a protein that is truncated within the extracellular, N-terminal domain (R110Pfs). We investigated the effect of this mutation on osteoclast formation, receptor localisation ...

ba0002p132 | (1) | ICCBH2013

Studies on bone and osteoclasts in patients with Shwachman Diamond syndrome

Helfrich Miep , Mellis David , Coxon Fraser , Greenhorn John , Kuijpers Taco , Crockett Julie

Shwachman Diamond syndrome (SDS; MIM 260400) is a monogenic, autosomal recessive, pancreatic condition often accompanied by low bone mass and fracture. In SDS, as in cystic fibrosis, a low bone mass may be secondary to poor nutrition or chronic low-grade infection, but it has also been suggested there may be a primary bone phenotype. Paradoxically, recent studies in cell lines and in a mouse knockout for the SBDS gene, have suggested changes in important osteoclast gr...

ba0002p138 | (1) | ICCBH2013

Rare mutations associated with osteoclast-poor osteopetrosis provide molecular insights into receptor activator of NFκβ signalling

Crockett Julie , Das Subhajit , Dignan Cahal , Mellis David , Duthie Angela , Sobacchi Cristina , Schulz Ansgar , Helfrich Miep

Twelve different mutations in TNFRSF11A (encoding the RANK receptor) have been associated with osteoclast-poor autosomal recessive osteopetrosis in patients. Two truncated RANK proteins resulting from substitution mutations (W434X and G280X), identified in two infants, cause loss of the intracellular oligomerisation motif and in the case of the G280X mutation the TRAF6 binding domain. A third mutation was identified in a 10-year-old patient and is a frameshift mutatio...

ba0005p195 | Cell biology: osteoclasts and bone resorption | ECTS2016

The role of LC3 and autophagy in bone resorption by osteoclasts

Tran Anh , Coxon Fraser , McDermott Emma , Ganley Ian , Odgren Paul , Martinez Jennifer , Green Douglas , Helfrich Miep

The autophagy protein LC3 is necessary for bone resorption by osteoclasts, although it has been suggested that this may be through a novel, autophagy-independent process, by promoting lysosomal fusion at the ruffled border (RB). This process would be analogous to LC3-associated phagocytosis (LAP), in which LC3 is acquired by phagosomes through an autophagy-independent process, and controls phagosome maturation by promoting fusion with lysosomes. We have investigated this possi...