Expression of type XIV collagen in developing chicken tendons: Associationwith assembly and growth of collagen fibrils

Collagen fibril assembly is a multistep process involving multiple macromol ecular interactions. Type MV collagen contains multiple domains and is capa ble of interacting nifh collagen fibrils and other extracellular matrix com ponents. During tendon development, naturally changing expression of type X IV collagen and its variants may modulate such interactions. Type XIV colla gen was studied using immunochemical and molecular approaches. Western anal ysis demonstrated that type XIV collagen content was high between days 14 a nd 19, decreasing sharply at hatching. Immunoelectron microscopy demonstrat ed that type XIV collagen was fibril-associated, with a periodicity of 67 n m, indicating specific interactions. Decreased fibril-associated reactivity for type XIV collagen was seen at hatching, indicating a removal of collag en XIV from the fibril surface. The expression of two NCI splice variants w as analyzed. Overall, type XIV collagen mRNA decreased significantly from d ay 14 to hatching. The long NCI splice variant was the predominant species at 14 days; at 19 days the two variants were expressed in lower amounts at nearly a 1:1 ratio; at hatching, both variants were expressed minimally. Ch anges in splice variant expression, suggest that different functional forms of type XIV collagen are present, allowing modified interactions with fibr ils during development. In conclusion, type XIV collagen is fibril-associat ed and developmentally regulated, Modulation of expression of the NCI splic e variants may mediate the fibril interactions that allow the transition fr om growing fibril intermediates to mature fibrils. (C) 2000 Wiley-Liss, Inc .