EXPRESSION OF TYPE-VI, TYPE-IX AND TYPE-XI COLLAGEN GENES AND ALTERNATIVE SPLICING OF TYPE-II COLLAGEN TRANSCRIPTS IN FRACTURE CALLUS-TISSUE IN MICE

The levels of six mRNAs coding for constituent alpha-chains of three m inor collagens of cartilage were analyzed in an experimental fracture model in normal and transgenic Del1 mice harboring a deletion mutation of exon 7 in the type II collagen gene. Reduced and retarded chondrog enesis in Del1 mice was evident in callus samples as reduced mRNA leve ls for the cartilage specific type IX and XI collagens at days 7 and 9 of fracture healing. Analysis of the calluses for alternative splicin g of pro alpha 1(II) collagen mRNA also suggested retarded chondrogene sis in Del1 calluses, Another developmentally regulated step in limb d evelopment, a switch between alternative promoters of the alpha 1(IX) collagen gene, was also seen during fracture healing but was less obvi ous in Del1 calluses, Finally, the current data suggest that the abnor mality in bone remodelling in Del1 mice involves activation of the gen es coding for alpha 1(XI) and alpha 2(VI) collagens.