For qRT-PCR, the rib cages from 5-day-old mice (wild type (wt) and mutant (m/m)) were dissected and treated with collagenase (type 1A, 2 mg/ml) for 1 h at 37°C in Dulbecco’s modified Eagle’s medium (DMEM). The costal cartilage was dissected from individual ribs, and the perichondrium layer was removed. The cartilage was digested a second time with collagenase for 3 h to remove the collagen matrix and release the chondrocytes. The chondrocytes were passed through a cell strainer (70 μm) and washed with DMEM containing 10% FBS and following centrifugation washed again with PBS. The cell pellet was resuspended in 500 μl TriZol (Invitrogen), and total RNA was isolated according to the manufacturer’s instructions. First-strand cDNA was synthesised using random hexamer primers (Superscript III, Invitrogen), and qPCR was performed using the SYBR® green PCR protocol. Primer sequences were: BiP: 5′-ggcaccttcgatgtgtctcttc-3′ and rev: 5′-tccatgacccgctgatcaa-3′; Grp94: 5′-taagctgtatgtacgccgcgt-3′ and rev: 5′-ggagatcatcggaatccacaac-3′; Calnexin: 5′-tga ttt cct ctc cct ccc ctt-3′ and rev: 5′-cac tgg aac ctg ttg atg gtg a-3′; Calreticulin: 5′-gct acg tga agc tgt ttc cga-3′ and rev: 5′-aca tga acc ttc ttg gtg cca g-3’; Erp72: 5′-agt atg agc cca ggt tcc acg t-3′ and rev: 5′-aga agt ctt acg atg gcc cac c-3′. Each experiment included ‘no template’ controls, was run in duplicate and had an 18S RNA control. Each independent experiment was repeated three times, and the results were analysed by independent-samples t test.
For Western blot analysis, chondrocytes were isolated as above, but aliquots of 2 × 105 chondrocytes were prepared and resuspended in 5× sodium dodecyl sulphate (SDS) loading buffer containing DTT. These protein aliquots were separated by 4–12% SDS-polyacrylamide gel electrophoresis (PAGE; Invitrogen) then transferred to nitrocellulose membranes for Western blot analysis. Ponceau staining was used to confirm equal loading of total protein isolates.
Antibodies to key chaperones associated with the unfolded protein response were used at a dilution of either 1:500 (BiP, Grp94, Erp72 and PDI; all from Santa Cruz) or 1:100 (ATF-6 from Imgenex and Bcl-2 from Abcam).
For Western blot analysis, chondrocytes were isolated as above, but aliquots of 2 × 105 chondrocytes were prepared and resuspended in 5× sodium dodecyl sulphate (SDS) loading buffer containing DTT. These protein aliquots were separated by 4–12% SDS-polyacrylamide gel electrophoresis (PAGE; Invitrogen) then transferred to nitrocellulose membranes for Western blot analysis. Ponceau staining was used to confirm equal loading of total protein isolates.
Antibodies to key chaperones associated with the unfolded protein response were used at a dilution of either 1:500 (BiP, Grp94, Erp72 and PDI; all from Santa Cruz) or 1:100 (ATF-6 from Imgenex and Bcl-2 from Abcam).
