Temporal and spatial transitions in collagen types during embryonic chick limb development

Abstract

To determine whether transitions occur in the types of collagen synthesized during embryonic chick limb development, the α chain composition of the collagens produced by whole limbs and various anatomical regions of limbs was analyzed at different stages (23–24 to 40). The tissues were incubated in the presence of 3H-proline and 3H-lysine and the α chain distribution of the purified, labeled collagens was determined by chromatography on carboxymethyl cellulose columns. We found that the stage 23–24 leg mesenchyme is producing predominantly, if not solely, an (α1) 2α2 type collagen (chain type as yet undetermined). At about stage 25–26 the limb core begins synthesizing detectable amounts of (α1) 3 collagen, which we presume to be cartilage type collagen, [α1 (II)] 3, while the outer portion of the limb largely continues to produce (α1) 2α2. The production of (α1) 3 collagen in the core progressively increases until, by stage 33 it is the only species detectable in the tibial diaphysis. Shortly thereafter (by stage 35 +–36) (α1) 2α2 type collagen reappears in the tibial diaphysis signifying the production of bone collagen, [α1 (I)] 2α2. During the next several days of incubation, the relative proportion of (α1) 2α2 increases in the bony diaphysis while (α1) 3 remains the predominant species synthesized in the cartilaginous epiphysis.