Haploinsufficiency of Bag-1 affects cartilage development and osteogenic differentiation in vitro

Abstract

Event Abstract Back to Event Haploinsufficiency of Bag-1 affects cartilage development and osteogenic differentiation in vitro RS Tare1*, PA Townsend2, GK Packham3 and ROC Oreffo1 1 University of Southampton, Bone and Joint Research Group, United Kingdom 2 University of Southampton, Human Genetics, United Kingdom 3 University of Southampton, Cancer Sciences, United Kingdom The Bcl-2-associated athanogene-1 (Bag-1) co-chaperone is expressed by chondrocytes and osteoblasts, and functions as a transcriptional regulator mediating chondrocyte differentiation and apoptosis in vitro (1). By utilising cell populations from a mouse model of Bag-1 haploinsufficiency (i.e. one Bag-1 null allele and one normal Bag-1 allele), this study aims to define effects of Bag-1 heterozygosity on formation of cartilage templates and osteoblast development. {BR}Micromass cultures of E11.5 Bag-1+/+ and Bag-1+/- mouse embryonic fibroblasts (MEFs), differentiated in presence of BMP-2 (100 ng/ml), ascorbate and beta-glycerophosphate, were utilised to model in vivo developmental stages in the formation of cartilaginous primordia. Cultures were analysed at days 7, 14, 21, 28, 35 and 42 for expression of Bag-1 and development of cartilage nodules. Bone marrow cells (BMCs) from 14-week Bag-1+/+ and Bag-1+/- mice were cultured for 21 days in media supplemented with either 10 nM Dexamethasone, 25 nM Calcitriol or 100 ng/ml BMP-2, to analyse their osteogenic response. {BR}During the initial 14-day period, significantly high Bag-1 expression was observed in micromass cultures of Bag-1+/+ MEFs compared to Bag-1+/- MEFs. The 14-day period of micromass culture is comparable to in vivo murine embryonic limb development at E10.5 and E11.5, associated with robust Bag-1 expression and formation of vital mesenchymal condensations prefiguring future skeletal elements. Significantly, days 7 and 14 of Bag-1+/+ MEF micromass cultures were characterised by the presence of cellular condensations and mineralised cartilaginous nodules were observed by day 42 of culture. Bag-1 haploinsufficiency compromised the ability of Bag-1+/- MEFs to undergo condensations and organise into defined cartilaginous nodules by day 42 of micromass culture. Moreover, morphologically distinct hypertrophic chondrocytes (characterised by increase in cell volume and hence, enlarged cell size) in lacunae were absent in day 42 Bag-1+/- micromass cultures. Bag-1 heterozygosity also compromised the ability of BMCs to undergo robust osteogenic differentiation, as demonstrated by a decreased osteogenic response of Bag-1+/- BMCs compared to Bag-1+/+ BMCs in presence of the supplemented osteogenic factors. {BR}Our results illustrate a role for Bag-1 in the critical phases of skeletal development, namely formation of the cartilage templates of endochondral bones and osteoblast differentiation.{BR}(1) Bone 2008;42:113-28 Keywords: Bones, Bone Research Conference: 2011 joint meeting of the Bone Research Society & the British Orthopaedic Research Society, Cambridge, United Kingdom, 27 Jun - 29 Jun, 2011. Presentation Type: Oral Poster Topic: Abstracts Citation: Tare R, Townsend P, Packham G and Oreffo R (2011). Haploinsufficiency of Bag-1 affects cartilage development and osteogenic differentiation in vitro. Front. Endocrinol. Conference Abstract: 2011 joint meeting of the Bone Research Society & the British Orthopaedic Research Society. doi: 10.3389/conf.fendo.2011.02.00066 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 30 Sep 2011; Published Online: 30 Sep 2011. * Correspondence: Dr. RS Tare, University of Southampton, Bone and Joint Research Group, Southampton, SO16 6YD, United Kingdom, rt2@soton.ac.uk Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers RS Tare PA Townsend GK Packham ROC Oreffo Google RS Tare PA Townsend GK Packham ROC Oreffo Google Scholar RS Tare PA Townsend GK Packham ROC Oreffo PubMed RS Tare PA Townsend GK Packham ROC Oreffo Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.