Zebrafish collagen XIV is transiently expressed in epithelia and is required for proper function of certain basement membranes

We found that zebrafish has two differentially expressed col14a1 paralogs. col14a1a expression peaked between 18-somite stage and 24 hpf, whereas col14a1b was first expressed at 32 hpf. To uncover functions of collagen XIV (COLXIV) during early embryogenesis, we focused our study on col14a1a. We characterized the α1 (XIV-A) chain as a collagenase-sensitive 200 kDa protein that formed dimer that could be reduced at high pH. As observed for the transcript, COLXIV-A protein expression peaked between 24 and 48 hpf. Using anti-sense probes and polyclonal antibodies, we show that col14a1a and its protein product COLXIV-A, are transiently expressed in several epithelia, including epithelia undergoing shape changes, such as the fin folds. In contrast, anti-COLXII antibodies stained only connective tissues. COLXIV-A was also detected in the BM, where it co-localized with COLXII. At later developmental stages, COLXIV-A was not expressed in epithelia anymore, but persisted in the BM. Morpholino (MO) knockdown of COLXIV-A provoked a skin detachment phenotype. Electron microscopy analysis revealed that MO-injected embryos lacked a lamina densa and lamina lucida at 24 hpf, and BM defects, such as gaps in the adepidermal granules, were still detected at 48 hpf. These BM defects were accompanied by a rupture of the dermis, and detachment of the epidermis. Taken together, these data suggest an unexpected role of COLXIV-A in undifferentiated epithelia and in the formation of embryonic basement membranes.