DEVELOPMENTAL REGULATION OF MESSENGER-RNA SPECIES FOR TYPE-II, TYPE-IX AND TYPE-XI COLLAGENS DURING MOUSE EMBRYOGENESIS

Several techniques were used to study the co-ordination of mRNA levels for five constituent chains of cartilage collagen fibrils during mous e development. Short cDNA clones were first constructed for mouse and human alpha 3(IX) and for mouse pro alpha 1(XI) collagen mRNA species. Northern analysis of developing mouse embryos revealed that the mRNA species for alpha 1, alpha 2, and alpha 3 chains of type IX collagen p eaked earlier than those for pro alpha 1(II) and pro alpha 1(XI) colla gen chains. Quantification of these mRNA species by slot-blot hybridiz ation confirmed this developmental regulation: the mRNA ratios for typ e II/type IX/type XI collagens changed from 5.7:1:0.6 (at embryonic da y 12.5) to 10.6:1:0.9 (in newborn mice). However, the genes coding for the three chains of type TX collagen seemed to be under more co-ordin ated regulation during mouse development. In addition to high mRNA lev els in cartilages and the eye, low levels of type IX collagen transcri pts were identified in brain and skin of newborn mouse using RNase pro tection and reverse transcriptase-PCR assays. Finally, hybridization i n situ revealed identical tissue distributions of the three type IX co llagen mRNA species during early chondrogenesis but somewhat more wide spread expression of the alpha 1(IX) and alpha 3(IX) mRNA species duri ng endochondral ossification at day 16.5 of embryonic development. The se results suggest a relatively tight coordination of the alpha 1(IX), alpha 2(IX), and alpha 3(IX) collagen mRNA species in chondrocytes, b ut a lack of co-ordination in several non-cartilaginous tissues.